IONIC BALANCE ANDGROWTH
OF PLANTS
C.T. DEWIT,
W. DIJKSHOORN ANDJ C NOGGLE
^k
CENTRUM VOOR LANDBOUWPUBLIKATIES EN LANDBOUWDOCUMENTATIE
CONTENTS
1 SUMMARY
1
2 INTRODUCTION
3
3 EFFECTS OFSALT SOLUTIONS ON THE IONIC CONTENTS OFPLANT MATERIAL . .
3.1
3.2
3.3
3.4
Summary
Short time uptake experiments
Ionic content ofleafmaterial
Conclusions
5
5
5
9
10
4 COMPETITIVE PHENOMENA
4.1 Summary
4.2 Models of competition
4.3 Examples
4.3.1 Growing plants
4.3.2 Excised roots
5 SELECTIVE ION UPTAKE BYGROWING PASTURE PLANTS
5.1
5.2
5.3
5.4
Summary
Experimental technique
Plantain
Orchard grass
5.4.1 Thefour-ion system
5.4.2 Themonovalent-ion system
5.4.3 Interaction between both systems
5.5 Anion uptake by perennial rye-grass
6 REGULATION OFTHE(C—Ä) CONTENT
6.1 Summary
6.2 Experiments
6.2.1 Cation replacement
6.2.2 Nitrate fertilization
6.2.3 Periodic harvests
6.2.4 Periodicharvests at twotemperatures
6.3 Discussion
7 IONIC BALANCEAND GROWTH OF BARLEY
7.1 Summary
7.2 Design ofthe experiment and yields
11
11
11
13
13
16
19
19
19
20
20
25
26
29
29
32
32
32
32
33
36
36
37
39
39
39
7.3 Ionicinterrelations
7.3.1 Potassium-calcium replacement
7.3.2 Application of chlorides
7.3.3 Fertilization with sodium
7.3.4 Fertilization withnitrogen
7.4 {C—A) content and yield
40
40
42
43
45
46
8 FURTHEREXPERIMENTSONTHERELATIONBETWEENNUTRIENTSUPPLY, (C—A)
CONTENT AND YIELD
8.1
8.2
8.3
8.4
8.5
8.6
8.7
Summary
Nutrient status,growthand yield
Shortage ofmicroelements
Potassium-sodium replacement
Application of chlorides
Ammonium fertilization
Buckwheat
9 IONICBALANCEOFPLANTAND SOIL .
9.1 Summary
9.2 External alkaline and acidiceffects
10 A TESTONTHEMACRONUTRITIONALSTATUSOF GRASS
10.1 Summary
10.2 Specific requirements
10.3 Thetest
10.3.1 Examples
10.3.2 Differences betweenplants and crops
10.4 Otherplant species
LITERATURE .
48
48
48
50
51
52
54
57
59
59
59
61
61
61
61
62
64
65
66
1 SUMMARY
Shorttimeexperimentswithexcisedroots showthat cationsand anionsfrom neutral
saltsarenot necessarily taken upinequivalent amounts. Sinceelectroneutrality must
bemaintained,anydifference betweenbothuptakesisbalancedbyexchangeofHC03~
or H + . Because oftheconcurrent changeinthe organicanion content the pH of the
plant material remains around 6.
The total cation content C equals K+ + Na+ + Ca++ + Mg++, and the total inorganic anion content A is NÛ3" + H2PO4- -f SO4-- + Q-. The N and Sin the
organicform arepresentinthereduction stageofNH3andH2S.Duringreduction of
NO3- and SO4--, the negative charge is released as HC03 - , which is either transformedintoanorganicanionorexchangedwithaninorganicanionfrom themedium,
or neutralised by H+ uptake. The ionic state of phosphate is not changed by its
utilization.
Thedifference betweenthecationandinorganicanioncontent,the(C—A) content,
isnumerically equal to the organic anion content.
Ion selectivity and related competitive phenomena were mainly studied for plants
growingonnutrientsolutionswithvaryingcation oranion composition.For cations,
two competitive uptake systems are distinguished: a four-ion system concerning the
ions K, Na, Mg and Ca, and a monovalent-ion system concerning K and Na. Both
systemsoperatein Gramineous species,whichdiffer from each otherbytheir relative
uptake of K and Na through the monovalent-ion system.The four-ion systemis the
onlyoneoperatinginplantain, sothat thisspeciestakesup theions,K, Na, Ca and
Mg competitively at about equal rates.
The anions N03~ and CI - appear to compete during the uptake by Gramineae.
Thedependence ofthe(C—A) content onthecomposition ofthe nutrient medium
was studied in experiments in which the nutrition is varied in such a way that the
growthisnot affected, but the anion and cation contentsvary over a widerange. In
these cases the plants appear to maintain their (C—A) content at a remarkably
constant value.Depending on growing conditions other than thecomposition of the
nutrient medium, this constant value is between 900 and 1100 me./kg for orchard
grassand perennial rye-grass.
It isinferred that a constant (C—A) content is not dueto the properties of the uptakeandutilization mechanismspersebut toaregulation ofitsvalueduring growth.
The arguments arethattheorganicNcontentisconsiderablyhigherthan1000gat./kg,
the equivalency of the (C—A) content and the organic anion content is maintained
throughout and that the (C—A) content is not constant in short time experiments.
Regulation in the topsis onlypossible ifsufficient organicanions and nitrates move
upward astheir saltsand organic anionsin excess of 1000me./kg (for grasses)move
again downward as their salts.
1
In small grains a stress on the (C—A) content develops when the availability of
cationsislow,the uptake ofinorganicanionswhich stayas suchin theplant ishigh
and thereduction ofnitratesin the shoots proceeds at a lowrate. This stress on the
(C—A) content isaccompanied bya reduction of the growth rate.
A reduced growth rate with a normal (C—A) content may also occur, but a low
(C—A) content is never accompanied by a normal growth rate. Hence, a normal
(C—A) content is one of the conditions for a good growth.
Normal growth ispossible at a wide variation of the Ccontent, the A content and
the contents of the individual ionic species, provided that the (C—A) content is
normal. This indicates that the organic anions are essential for good growth. The
cations are onlynecessaryin amounts above 250me./kgfor K and 50me./kgfor Ca
andMgbecausetheyformneutralsaltswiththeinorganicandorganicanions.Among
thesecationstheKionplaysadominant roleasapositivechargebecauseitisreadily
taken up by most plant species. However, it can be replaced in this respect by Na,
Ca and Mgwhenthese are readily taken up.
An excessive Ccontent or (C—A) content may occur in the case of K shortage in
thepresence ofanyothercationwhichisreadilytaken up.Although these otherions
may function as a positive charge, the K ion seems to be the only one which accompaniesthe excess organic anionsin their downward movement.
Withammonium fertilization growth proceeds often at a lower rate.This is due to
astressonthe(C—A)contentbecauseofcompetitionbetweenNH4+andothercations
andthe release ofH+ions duringthe organicN formation.
Aflowchart, summarizingthe present knowledge with respectto the evaluation of
thenutritional status ofgrassplantsisgiveninfigure37.Thisflow chart can not be
used for other species because they may differ in the relative uptake of cations
(plantain) orinthenormal (C—A) content (buckwheat, beets).
2 INTRODUCTION
I n a review o n t h e physiological basis for assessing t h e nutritional requirements of
plants U L R I C H (1952) showed that for t h e elements incorporated in t h e organic m a terial, analyses of the plant for the anions N O 3 - (in case of nitrate supply), S O 4 - a n d H2PO4- ismore informative with respect t o t h enutrient status t h a n analyses for
total N , S a n dP . W i t h sugar beets, nitrogen shortage is absent if thenitrate content
of the petioles of recently matured leaves is higher than 75 me./kg 1 . DIJKSHOORN
(1958), VAN B U R G H (1962), DIJKSHOORN, LAMPE a n d VAN B U R G H (1960) a n d D I J K S -
HOORN a n d LAMPE (1961) showed t h a t t h esupply of N , Sa n dP is sufficient for grass
if the NO3-", S O 4 - - a n d H2PO4- content is higher t h a n a b o u t 100,50a n d20 me./kg
respectively.
A differentiation cannot be made for the cationic elements because they are n o t
subject t o distinct chemical transformations. With the elements K a n d C a definite
deficiency symptoms develop insmall grains atcontents lower t h a n 200a n d50 me./kg,
respectively (LUNDEGÂRDH, 1951). F o r M gt h elevel is also a b o u t 50me. (BROESHART
a n d VAN SCHOUWENBURG, 1961), a n d only traces ofN a m a ybe necessary. But plants
m a y still respond t oa supply with these elements when thecontents arehigher. Hence
the diagnostic value of these limits is restricted.
Therefore, m u c h attention has been paid t o t h e contents of cations relative t o each
other, especially in view of the findings of VAN ITALLIE (1938, 1948) a n d BEAR (1950)
on t h e constancy of the equivalent s u mof the cations. They showed that in a rather
remarkable n u m b e r of cases t h e cation equivalent sumis a constant function oft h e
cation composition of t h e nutrient medium, provided that t h e anion composition is
n o t varied. W i t h varying anion composition of the medium, t h e cation content m a y
vary, b u tt h e ratio of cations a n d anions taken u p wasfound t o be a r o u n d 0.8. This
correlation between cation a n danion uptake wasconnected with themaintenance of
electroneutrality during uptake.
T h e w o r k was expanded by SCHARRER a n d J U N G (1955, 1956), DIJKSHOORN (1957)
a n d SAID (1959) w h oshowed t h a t theratio of cation a n danion uptake m a y decrease
with increasing nitrate metabolism (table 10). I t was assumed that t h e uptakes of
cations a n d anions from neutral salts a r e directly coupled a n d t h a t when t h e anion
is nitrate, its transformation into t h e nonionic, organic form releases its negative
charge internally as H C O 3 " , a n dthat this H C O 3 - m a yexchange with another anion
from t h e medium.
I t will beshown inthis p a p e r that this assumption isa tvariance with results of short
time experiments with, for instance, excised roots, a n d t h a t t h e combined evidence
1
All weights concern dry matter, unless otherwise stated.
obtained in other fields of research necessitates to assume that the organic anion
content is regulated by growing plants. For this purpose short time experiments on
the uptake and competitiveinteractions ofcations and anions withexcised roots are
consideredin sections3and4.In section 5experimentsarediscussedwhich,ifbased
on the evidence of sections 3and 4, should have resulted in a largevariation of the
organicanioncontent,butwhichinvariablyshowedtheabsenceofthisvariation and,
therefore, rendered it necessary to assume that the organic anion content is subject
to regulation.
Subsequently,theimplicationsofthisregulationwithrespecttothecomposition and
the growth of plants are studied more in particular with respect to the agricultural
aspects.
Speculations regarding thephysiologicalmechanismsinvolvedintheregulation observed proved to beunfruitful and arenot included.
EFFECTS OF SALT SOLUTIONS ON THE I O N I C
CONTENTS OF PLANT MATERIAL
3.1
SUMMARY
Evidence from literature is presented to show that the uptake rates of cations and
anions may differ considerably depending on the salt used. The difference does not
result in a change of pH of the plant material, but at any time and in any part of the
plant the difference between cations and inorganic anions equals the organic anion
content.
3.2
S H O R T TIME U P T A K E E X P E R I M E N T S
LUNDEGÂRDH and BURSTRÖM (1933) studied systematically the 10-hour uptake of
cations and anions by young wheat plants from different neutral salt solutions at
different carbon dioxide and oxygenpressures.Theuptake ofcationsisplotted against
the uptake of anions in figure 1. The observations show that cations and anions of
neutral salts are taken up at unequal rates.
Cotions
50
100
10" 3 m«.Anion*
F I G . 1 The net uptake of cations and anions by 14 young wheat plants from 13 different salt solutions at various CO2 and O2 pressures of the air used for aerating during 10 hours. D a t a of
LUNDEGÂRDH and BURSTRÖM (1933).
The uptake of cations and anions by excised roots of barley was studied also in
detail by ULRICH (1941). His results are given in figure 2a. The uptake of the positive
and negative ions from the neutral salts proceeds apparently with largely different
rates. K+ is taken up rapidly and Ca++ is taken up slowly, independently of the uptake rates of the anions such as S O 4 - - and Br~.
These observations agree with the concept of paired uptake only if excess cation
uptake isbalanced by the uptake of O H - or HCO3-ions and excess anion uptake by
the uptake of H+. Another viewis that the excesscation uptake is associated with the
exchange of H+ and excess anion uptake with the exchange of O H - or HCO3-ions.
Experiments with labelled HCO3" ions in the solution were carried out (OVERSTREET,
RUBEN and BROYER, 1940; JACOBSON, 1955 and HURD, 1956) to distinguish between
both possibilities. But the interpretation of these experiments is difficult because the
specific activity of the bicarbonate is likely to change owing to the relatively large
amounts of bicarbonate associated with the living material and because the entrance
of C* is not indicative of the entrance of HCO3-. Obviously, there is no coupling
between thecation and anion uptake from neutral saltsand, atleastinbalance studies,
the distinction between exchange with H+ or HCO3- and paired uptake with these
ions is rather academic.
The amount of buffering compounds inside the plant material is small compared
withchangesinioniccontents dueto salttreatments. Hence,ifexcesscations are taken
up with HCO3- or exchanged against H+, the internal pH must increase or the basic
bicarbonate ion has to be transformed into the slightly basic carboxylate anion. The
question of whether a difference between cation and anion uptake is accompanied by
a change in internal pH or by a change in the carboxylate content is of course not
academic and can be investigated.
ULRICH determined also the change in organic anion content in the barley roots used
in the experiment of figure 2a. The difference between the uptake of the cation and
the anion is plotted against the change in the organic anion content in figure 2b.
Irrespective of the salt given, the cation minus anion uptake is practically equal to
the changeinthe organicanions.Exceptions occurredwith (NH,i)2S04and Ca(N03)2,
probably because the N ofNH4+and NO3-isincorporated into the organic material,
so that changes in N content do not reflect changes in ionic content of the plant.
JACOBSON and ORDIN (1954) avoided any complication due to exchange and metabolism by not using nitrogen salts and by taking into account the exchange of ions
not given as a salt. The ionic content of barley roots before and after treatment for
three hours with four different solutions are given in figure 3a. The cation and anion
contents changed markedly due to the treatments. In figure 3b the organic anion
content of the roots is plotted against the cation minus inorganic anion content. Both
changed because of the treatments, but to the same extent. Consequently, cations,
balanced by HCO3- ions, are practically absent and there is no evidence of other
ionic components present in amounts comparable to the cation, the inorganic anion
and the organic anion content. The initial organic anion content of the barley roots
was about 10me./kg fresh weight and a three-hour treatment with KHCO3 doubled
this content. Apparently, the rate at which the roots are able to form organic anions
under the influence of a suitable salt treatment is large.
A Org.Anions
me./l
1:1
60
/ S
30
y/
20
'0
me./l Anions
10
9
/\
S
I
I
30
60
me /I Cotions- Anions
FIG. 2 a.Theuptake ofcationsandanionsbyexcisedbarleyroots during 8hoursfrom ten different
salts, as determined by changes in the solution, b. The change in organic anion content andthe
cation minus anion uptake,perliter ofrootsap.
Thenumbersrefer to: 1.CaS0 4 ; 2.KBr; 3.K 2 S0 4 ; 4.KH2PO4;5.K-citrate; 6.KHCO3;7.KNOs;
8. (NH 4 ) 2 S0 4 ; 9.CaBr2; 10. Ca(N0 3 ) 2 .
Data of ULRICH (1941).
Cotions
me./ kg fr. 5
Org.Anions
me./kgfr.
20
me./kgfr. Anions
40
20
me./kgfr.Cotions-Anions
(0
FIG. 3 a.Thecationandanion content ofbarleyrootsbefore andafter athreehour treatment with
four solutions.
b. The content ofthe organic anions andofthe cations minus anions.
The numbers refer to: 1.initial; 2.nosalt; 3.KBr; 4.CaBr2; 5.KHCO3.
Data of JACOBSON and ORDIN (1954).
FromCaBr2theCa++uptakewassmallerthantheBr~uptake,andtheorganicanion
contentofthetissuecorrespondinglydecreasedduringthetreatment.TheBr-uptake
waseven higherfrom KBr than from CaBr2and the K+uptake washigher than the
Ca++ uptake,whichindicates association between cation and anion uptake.It seems
thatthereisalimittotheexcessofanionuptakerateovercationuptakeratebecause
the organic anions available for breakdown in this process are present in restricted
amountsandtheplantmaterialcannotmaintainaprocessresultinginamarked drop
of theinternal pH (ULRICH, 1941).
An upper limit in the organic anion accumulation rate, andtherefore in the excess
cationuptakerate,isalsoprobable.Thisupperlimitmaybereachedwhenasaltwith
a readily accumulating cation and a slowly accumulating anion is given at a higher'
concentration. To test this the uptake from Rb^SCUand RbCl at concentrations of
10 -4and 10"2eq./l bybarleyroots,wasdeterminedwithamodifiedEpsteintechnique,
asdescribedbyNOGGLE, DEWIT and FLEMING(1963). Theresultsaregivenintable1.
TABLE 1 Uptake rates in 10~6eq./(140 min. g fresh) of the ions from RbCl and R02SO4by barley
roots at concentrations of
IO-4 eq./l
RbCl
RbS0 4
10-2 eq./l
Rb+
Cl-
SO4--
Rb+
CI-
SO4-
6.9
6.2
4.6
—
—
0.1
23.0
12.0
18.7
—
—
0.5
The Rb+ uptake rate at 1(H eq./l isthe same from the CI-and the SO4-- salt, although the CI- uptake is large and the SO4-- uptake negligible. This proves again
theabsenceofanydirectrelationbetweencation andanionuptakerate.Ataconcentration of 10-2eq./l the S04— uptakeis stillnegligible and the CI- uptake is large.
Butnowthe Rb+uptakefrom RbClisconsiderablyhigherthantheRb+uptake from
Rb 2 S0 4 . This association between cation and anion uptake at high concentrations
may be due to a maximum excess cation uptake rate, originating from a maximum
in the production rate of organic anions. Here, thismaximum is about 12.10-« eq./
(140 min. g fresh) which is in the same order of magnitude as the organic anion
production rate under the influence of KHC0 3 in the experiment of JACOBSONand
ORDIN (figure 3).
Thepromoting effect of Ca salts on the K+and Rb+uptake issometimes(BRIGGS,
HOPEand ROBERTSON, 1961)ascribed toapossiblyincreased anionuptake caused by
the addition oftheanion withtheCa salt,although VIETS(1944)showedthatit also
occurs with addition of CaS0 4 . NOGGLE, DE WIT and FLEMING (1963) observed a
large increasein Rb uptake by barley roots whilereplacing Rb+with Ca++,keeping
the CI- concentration the same (4.3.2). This showsthat the promoting effect of Ca
on the Rb uptake isnot due to a coupling between cation and anion uptake.
8
3.3
I O N I C CONTENT OF LEAF MATERIAL
The elements K, Na, Ca and Mgare predominantly in their ionic form inside the
plant. Sinceminor elements and organic cations are quantitatively negligible,the total
cation content ofplant material isequal toC= K+ + Na+ + Ca + + + Mg + + equivalents. Itwillbeshown insection 8.6that thecontribution ofNH4+tothetotal cation
content is small even when N isgiven as ammonium.
Phosphate ispresent either asthe inorganic anion orinphosphorylated compounds.
In both cases it corresponds with theionic form of H2PO4- (seealso figure 4). The
nitrogen is present either in thereduction stage of NH3 or as NO3-. It contributes
only in the latter form to the inorganic anion content. Sulphate is present inthe
reduction stage ofH2S orinthe inorganic form SO4--. The organic sulphur content
of the protein ofgrasses, expressed in me. SO4--, is about 0.054 times the nitrogen
content ofthe protein expressedin gramatoms (DIJKSHOORN, LAMPE and VANBURGH,
1960). The SO4-- content can therefore be calculated from the total S content by
substracting this calculated organic Scontent. CIisintheinorganic Cl~ form inthe
plant. Therefore, thetotalinorganic anion content isequaltoA = NO3"+ H2PO4" +
+ SO4-- + CI-me.
Org.Anions
mt./kg
Org.Anions
me./kg
(000
4000 -
2000 -
2000 -
2000
4000
ma./kg (C-A)
0
2000
4000
m«./kg C-(N0J*Cl"*S0/"+P0/~")
Fio.4 a.The relation between theorganic anion content andthe (C—A) content ofthe leavesof
12plant species.Aisslightly overestimated becauseitincludestotal sulphur. Phosphate isincluded
asH2PO4-.
b. Asfigurea,butphosphate asPO4—. The (C—A) content and organic anion content are notat
allequivalent when phosphate isincluded asP O 4 — orHPO4—.
Thenumbersrefer to: 1.limabean,2.peas,3.alfalfa, 4.soybean,5.beets,6.spinach,7.buckwheat,
8. blue grass,9.wheat, 10.tomato, 11.lettuce, 12.cantaloupe (pH cellsap 7.5).
Data of PIERCE and APPLEMAN (1943).
PIERCE and APPLEMAN (1943) determined the (C—Ä) content andthe organic anion
content of 12 plant species (figure 4a). Theobservations areclosely against the 1:1
line,whichindicates that,inleaves,the excessofcationsisalsobalanced by organic
anions. Only the (C—A) content of cantaloupe is considerably higher than the
organicanioncontent,whichwasfound to correspondwithahighervalueofthe pH
ofthecellsap.
Infigure4b,the phosphate content is calculated as PO4 . The scattering of the
observations is now considerable, which shows that phosphate should be expressed
as monovalent.
DIJKSHOORN (1962) determined the organic anion content and (C—A) content of
perennialrye-grass,grownasdescribedlaterinthispaper.Hefound a(C—A) content
of 1100me./kgandanorganicanioncontent of 1000me./kg.Theexcessalkalinityof
1100—1000= 100me./kgmayrepresent other organicions,HCO3-,ormay reflect
analytical errors.
3.4
CONCLUSIONS
In short time experiments there appears to be no relation between the uptake of
cations and anionsfrom neutral salts.Any difference between the uptake of cations
and anions and any reductive assimilation of nitrate and sulphate is reflected in a
correspondingchangeoftheorganicanions,andat anytimein anypart ofthe plant
thedifference betweenthecationandanioncontentispracticallyequaltothe organic
anion content.
It is often concluded from these short time experiments that for growing plants
differences incationandanionuptakeandinreductiveassimilationofions,andthereforeintheorganicanioncontentcanbeeasilyinducedbyvaryingthesupplyofcations
and anions (compare CARLES, 1960). It is not difficult to find experimental results
(compare section 7)whichmaysupport this conclusion.
However, suchconclusions are not consistent withthefindingsof BEAR (1950) and
others on the constancy of the total cation content and of the cation-anion ratio in
plants, indicating regulation that comes to the fore when growing plants are considered. Such a regulation is not necessarily absent in short time experiments with
excisedroots,butitmanifestsitselffar morepronouncedwhenintactplants,growing
under normal conditions,are considered.
To study this regulation it is desirable first to determine to what extent different
plantspeciesmayshowpreferencefordifferentionsandandthispreferenceismodified
bycompetitive phenomena.
10
4 COMPETITIVE PHENOMENA
4.1
SUMMARY
Some well-known mathematical models of competition are discussed and applied to
uptake data for whole plants and excised roots. In this way it appears possible to
discriminate between competitive and other interactions.
4.2
M O D E L S OF C O M P E T I T I O N
The n equations
17.=
1
bEl
hEx + b2Ez+ . . . . + bßt + . . . . + bnEn + 1
Mi<°°>
W
(i)
withy = 1,2,3
,i,
n and withproper designations for the symbols are widely
usedto describecompetitive phenomenainphysicalandchemicalengineering,physical
chemistry, plant ecology (DE W I T , 1960) and animal ecology (VOLTERRA, 1928).
EPSTEIN and HAGEN (1952); FRIED and NOGGLE (1958); SCHUFFELEN (1954) and
othersusedtheseequationstoevaluatewhethertwoionsaffect eachother competitively
during the uptake by excised roots. In this case £ i , E%,....En represent the concentrations ofions ofthe same signintheroot medium, U{istheuptake ofionicspecies i,
Mi(a,) is the (extrapolated) value of t/j at infinite concentration of this ion only, and
bi is a constant. The constant 1 in the denominator reflects the dependence of the
competitive phenomena on concentration.
A concentration series of ion species 1 is defined as Ei variable and Ei,... ,Ej
En each constant.
A replacement series of the ion species 1 and 2 is defined as £ i + £2 = £1+2 =
constant and £ 3 , . . . , Ej,..., En each constant, hence an experimental series where
the total concentration of ions in the medium is the same but the ratio of two varies
between treatments. They enable the study of competitive phenomena between ions
of one sign of charge without varying the ions of the other sign of charge in the
treatment solution.
The factor
1 + S bjEj
3
can be eliminated with advantage by the following rearrangement. The abbreviation
D is used for
11
n
p. _L_ /T„
2
1 + S bfi) and D V
3
( = 2))
-Cl+2
is substituted for thisfactor in equation (1).Then
Ü! =
^ L
biEi + b2E2+ — {Ei+ E2)
E
6X
,A , D s . ' '
?T^M
i+v
^ÔT:
MX™
(2)
Now
Afi =
L ^ ^(oo)
— A/ifa>)
(3)
-£"1+2
isthe uptake of species 1 for Ei = Ei+z and E2 = 0.The constant
*•=(*'+£;)
<4>
is called the crowding coefficient of ionic species (1). Equation (2) can now be rewritten as
TT
k\E\
k\Ei + k2E2
k\2E\
K12E1 + E2
fc,
for species 1 and
U2 =
kaE
*
for species2.
Onlytherelative crowding coefficient
kiz =
hi
k2
can be determined in a replacement series.
Therelation between the concentration and theuptake for w i . • • ,.
relative crowding coefficient is 1.Thisis the a ewhen * - h T "
,
the values of*, when E1+2 is small compared witlD
m J ^ t ^ ^ T
coefficient isnot equalto 1,therelations betweenu p t a k e ^
' ^ ^
f r b th
ions are curved to the sameextent but in o p ^ T e c t i ' s ^ ^ ^
° °
Therelativeuptake of twoionsin a replacement seriesisgivenby
k
WE*
"-M7
andis a constant function ofthe ratio betwppn +v.„• •
12
(6)
(7)
concentration series for both ions. Instead of using equation (3) it is convenient to
express this equation for the concentration series directly into Mi, ki and £1+2,the
latter value being the maximum value of E\ in the concentration experiment. This
results in
(fci—l)Ei +E1+2
Thisequationisobtainedbysubstituting 1forki andE\+z—E\for£2inequation(5).
Finally,equation (5)isextendedto a replacement seriesofnionsbythenequations
Ui—^^-Mi
XkjEj
(9)
with Ei + Ei + . . ..Et + .... En = constant.
DE WIT (1960) gives more mathematical details and shows that at this stage two
models of competition have to be distinguished.
Model 1. The observations of a replacement series fit equations (5) and those of a
concentrationseriesequation(8)andthevalueofk\2inequation(5)canbecalculated
from the constants k\ and ki in equation (8)with equation (6).Onlyin this case the
datafitthe original equations(1).
Model2.The observations ofareplacement seriesfitequation (5);thoseofaconcentrationseriesmayormaynotfitequation(8),butthevalueofkiz cannotbecalculated
from the constants k\ and ki in equation (8). In this case the data do not fit the
original equation(1).
In plant ecology and animal ecology (DE WIT, 1960) competition according to
model 1is exceptional, but competition according to model 2 is not unusual. In
physical chemistry it often is not possible to test the validity of model 1 because
concentration series cannot berealized. In thesefieldsof studytheterm competition
isnot restrictedto model 1.
In case ofion uptake studies by growing plants the cation uptake often dependsin
someway on the anion uptake. In such casesit is not possible to interpret concentration experiments as described. The term competition ishere also not restricted to
model 1 ifthereis somecircumstantial evidencefor usingthisterm.
To clarify the use of these equations examples ofmodels 1and 2are given. Oneof
these examples is also used to prove that competition between monovalent and
divalent ions occurs.
4.3
EXAMPLES
4.3.1 Growingplants
With growing plants there is interaction between the cation uptake and the anion
uptake. Since a cation cannot be added to a nutrient solution without adding an
13
anion, complications duetothisinteraction oftheionscannot beavoided in concentration experiments. Hence, to study selectivity and competition only replacement
seriescan beused.
Thetechnique of replacement experiments will be discussed in 5.2. As an example
theresultsoftworeplacementseriesaregivenhere,whichconcern Na-K replacement
withperennial rye-grassand orchardgrassasperformed by SAID(1959).Thecomposition of the herbage isplotted against theinitial concentration of the replaced ions
in the treatment solution of figure 5a and b. The K and Na contents of the plants
me./kg
ma./1
me./l
Periodofregrowthonthetreatments;33 ^ S ° * = °' S ° 4 "" °'Q :°'
Renewalofsolutions
. 0x
Averageyieldpercontainer
• io s
Data of SATO(1959).
'
grown without these elements in the treat™™*e~i*•
ions were introduced withthe^ n ^ < £ £ ? T ** ™° ^ ^
**"
K-load, the Na-load etc. The l ^ T d î L
Z
™° S U P P l y " " C a U e d t h e
of the presence of these^ 0 J ^ ^ £ ^ ^ DOt affeCt t h e * e l d b e C a U S e
treatments and theloads aret h u P t a L < l w * ! " ***** * ? - " **"
The K uptake line curves u p w j ^ ^ ^ v ' 0 0 " ' " ^
same extent. This indicates that a t r e a ^ n t t c o r H
"*^
^ ^ ^ t0 ^
e q U a t i Q (5) Can b e U S e d
inthegraphs
a eare
X obtained
i L
f described
^ '°
vThecurvesasgiven
.
gwpns
as
bv° DEWIT nQfi(V> These
huesrepresent equaùon (5)withthe constants listedin table 2.
14
TABLE2 Values ofM,k and a forthe curves infigure5.
Afna
&kna
Qkna
m«./l
perennial
rye-grass
orchard
grass
880
800
2.0
2.2
860
490
2.5
4.4
me./kg
me./kg
mi./l
FIG. 6 Mg-Careplacement diagramfor theherbage ofperennialrye-grass(a)andorchardgrass (b),
grown inmixed culture. Initial composition ofthe solutions inme./l
Mg :x,Ca:6—x,K :1.5, Na:0, NO3 :6,H2PO4 :0.5,SO4 :1,CI : 0.
Period ofregrowth ontreatments: 3weeks
Renewal ofsolutions
: 0x
Average yield per container
: 12g
Data of SAID (1959).
The relative uptake akna is calculated from thethree other constants according to
equation (7), and characterizes the difference between both grass speciesasfarasthe
uptake ofK andNaisconcerned. This difference ismostly due tothedifference in
Mna.
Sinceitiswell known that monovalent ions may affect each other's uptake adversely
in short time experiments with barley roots (EPSTEIN andHAGEN, 1952), the K-Na
interaction ishere anexample ofcompetition according tomodel 2. Because concentration experiments cannot beexecuted without introducing anion effects, it cannot
be tested whether thetwo ions compete according tomodel 1.
The result ofa Ca-Mg replacement series with both plant species isgiven in figure
6a andb (SAID, 1959). Theobservations are on straight lines so that the relative
15
crowding coefficient is 1in both cases. Theconstants in equation (5)aregivenin
table3.
TABLE3 Values ofM, k anda forthecurvesinfigure6.
A/mg
ATcamg
a
camg
perennial
rye-grass
orchard
grass
310
380
1
0.82
220
500
1
0.44
me./kg
me./kg
It maybethat the Cauptake andtheMguptake areboth proportional to concentration andindependent ofeach other. Experiments with excised roots donothelp
much to distinguish between such a peaceful coexistence and competition with a
relativecrowdingcoefficient of1 becauseinthiscasetheuptake ratesofdivalentions
are smallcompared withtheinitialexchangereactions.
4.3.2 Excisedroots
Thereisverylittlerelationbetweencationuptake andanion uptakebyexcised roots
FIG. 7 CaandRbuptake ratesbyexcisedplantainrootsfrom theirchloridesaltsat concentrations
around 10me./l.
a. Concentration series,b.Replacement series.
The lines in figure b were calculated according to competition model 1with thedata in figure a.
Data of NOGGLE, DE WIT and FLEMING (1963).
16
(3.2). Hence concentration experiments can be interpreted without paying undue
attention to the other ion of the salt.
NOGGLE, DE W I T and FLEMING (1963) studied the interaction between Rb and Ca
uptake of excised roots of barley and plantain (Plantago lanceolatd). Two of the
experiments will be discussed here to show an example of competition according to
model 1and of a much more complicated interaction.
The results of a Rb-Ca replacement series with plantain roots at a concentration
levelof 10~2eq./l of their chlorides are givenin figure 7b.The Ca-lineis bent upward
and the Rb-line is bent downward. This indicates competition according to model 2.
Theresults oftwoconcentration experimentswiththeseelements aregiveninfigure7a.
These fit equation (8)with Afrb = 4.8,Afca = 6.5 units,fcrt>= 1and kca. = 4. Hence
the relative crowding coefficientfccarbin equation (5)is equal to 4/1 = 4. The curves
for the replacement series calculated with these constants are given in figure 7b and
pass there through the observations. Apparently the data are not at variance with the
supposition of competition according to model 1. But at concentrations around
10 - 4 eq./l the two ions suppress each other's uptake also in some other way besides
competition according to model 1 (NOGGLE, DE W I T and FLEMING, 1963).
One may question whether the basic equation 1holds for a mixture of monovalents
and divalents. But, even when the interrelations are governed by exchange reactions,
the data have to be much more accurate and to extend over a wider range to find
any effect of the valency not accounted for by the values of k.
10"7eq
g KO min.
100
50 -
0.5
10-*iq.n
10"* «q./l
FIG. 8 Caand Rbuptake ratesbyexcised barleyroots from theirchloridesaltsat concentrations
around 10-1me./l.
a. Concentration series,b.Replacementseries.
Thefull drawn lineinfigure b wascalculated according to competition model 1with the data in
figure a.Dataof NOGGLE,DEWrrand FLEMING(1963).
17
The result of a similar experiment with barley roots at concentrations around 10~4
eq./lisgiven infigure8a and b. Based on the results of the concentration serieswe
calculated the solid lineinfigure8bfor the replacement series.But the observations
for Rb are on the dotted line, so that it is obvious that theinterrelation is not competitive. The Rb uptake in the presence of Ca is even larger than in the absence of
Cain spite ofthe lower Rb concentration. Thisisknown asthe VIETS effect.
A further analysis (NOGGLE, DE WIT and FLEMING, 1963) showed that the Rb uptake rate in the absence of Ca cannot be maintained, but in the presence of Ca it
behaves as other ions. Hence, this VIETS effect is of small importance for growing
plants supplied withreasonable amounts of Ca.
The VIETS effect occurred also at concentrations around 10-2 eq./l, although to a
smaller extent. Here the Ca uptake was measurable and appeared to be depressed
markedlybythepresence of Rb, indicating someform ofantagonistic effect between
this monovalent and thisdivalent (figure9).
itr 7 «q.
g HO min.
200
X
X
/•*.
100
-/
•
•
n
_
0.5
1
10"'»q.Co/l
X CaCI,
Co: :Rb
FIG. 9 The Ca uptake from CaCl2 at concentrations around 10me./linaconcentration series and
a replacement series with Rb. Data of NOGGLE, DE WIT and FLEMING (1963).
18
SELECTIVE ION UPTAKE BY G R O W I N G
PASTURE PLANTS
5.1
SUMMARY
The effect ofvaryingcation or anion concentrations on thecomposition ofthe herbage
is studied by means of an experimental technique developed by DIJKSHOORN (1956)
and SAID (1959) and with the aid of the considerations presented in section 4.
It is shown that two competitive systems are operating for the cations. The four-ion
system concerns K, Na, Mg and Ca and the monovalent-ion system K and Na. Both
systems operate in grass, but in plantain only the four-ion system operates. The occurrence of competition between NO3 and CI is also shown.
5.2
EXPERIMENTAL TECHNIQUE
Selectivity experiments with growingplants have been restricted to replacement series,
to avoid interaction between cation and anion uptake. If in a nutrient solution one
cation is replaced by another, the growth of the plants may be affected. This is likely
to change the properties of the plant and to induce different degrees of exhaustion of
the nutrient medium.
According to DIJKSHOORN a good growth rate, not affected by the composition of
the treatment solution, is obtained when: (1) nitrate is supplied with the treatment
solution, and (2) a reasonable supply of other elements is secured by starting an
experiment with clipped plants and restricting the regrowth to some weeks.
The grass species orchard grass (Dactylis glomeratd) and perennial rye-grass (Lolium
perenne) and the dicotyledonous herb plantain (Plantago lanceolata) were used. The
plants were taken from a normally fertilized field, therootswerecleaned andfor each
treatment plants mounted in perforations of 30 x 20cm covers of 6-liter containers.
Subsequently the plants were clipped at 3cm above the covers and transferred to the
treatment solutions. Regrowth during two or three weeks took place in a greenhouse
at 20-25 °C. No experiments were made during the winter.
During regrowth the transpired water was replenished by demineralized water. The
regrowth, collected by clipping again at 3 cm, was dried, weighed and analysed.
Sometimes the remaining plant parts were also harvested, the roots being rinsed in
running tap water.
The dryweight ofthe startingmaterial variedbetween experiments,butwasthe same
for different replacement series of one experiment. The weight of the clipped plant
material was about 40 g, that of the regrowth about 15g and the total plant weight
19
at the end ofthe experiment was about 60g. Within a seriesthe yield did not vary
systematically with treatments.
Thetreatments canbevariedbyrenewingthetreatment solutions0 x , l X , 2 x . . . .
duringthe period ofregrowth.Experiments withsomenutrient exhaustion appeared
togivemoreinformation thanexperimentswithoutexhaustion.Moreover,thepractical valueis obvious becauseplantsin thefieldare also subject to exhaustion during
growth.
In a series of experiments the sum of the four cations was kept the same, and one
or more of thefollowing replacement serieswereprepared:
-Ek+ -Ena= \ S E
Eca, = Emg = \ S E
andinthesamewayfor K-Ca, K-Mg,Na-Mg,Na-Caand Mg-Careplacementseries.
Thesymbol Sisrepresentsthetotalinitialcationconcentrationinme./landthe other
symbols the initial concentrations of the ion species employed. Similar series were
made for the anions NO3-, H2PO4-, Cl~and SO4--.
Treatments with one of the ions at zero supply were at first not used. When the
disadvantage of this omittance became apparent they were included.
The treatment solutions were prepared by adding 1N stock solutions to 6liters of
demineralized water. In the case of less soluble salts slight differences between the
replacementseriesastotheiranioniccompositionwereintroduced. Althoughthisdid
not lead to any serious diificulties with the interpretations it would have been wiser
to avoid this complication instead of some work.
The weights of the plant material were determined after drying at 105°C, and the
contents were determined with an error of about 5 per cent according to routine
procedures usedat the Institute in Wageningen. They are givenin me./kg dry matter
(N, P, CI,K, Na asmonovalents and S,Ca and Mgas divalents).Kjeldahl nitrogen
includes onlyfrom 40to 80percent ofthe nitrate present and may haveledto some
underestimation ofthe total nitrogen content at contents above 2000me./kg (DIJKSHOORN and LAMPE, 1960).
5.3
PLANTAIN
The cation content of the herbage of plantain grown on K-Na, K-Ca, Ca-Na and
Ca-Mgreplacement seriesisgiveninfigure10.Thetreatment solutionswererenewed
onetime.The degree of exhaustion isnot known because the wholeplants were not
analysed, but conductivity measurements indicated that it did not exceed 50per cent
before renewal of the solutions. The yield was a constant function of the treatment
differences so that content minus load (content at zero supply of the cation) is the
uptake by the herbage.
Thecationcontentsareonapproximately straightlines,sothattherelativecrowding
coefficient in equation (5)is about 1for all combinations. The values of M read in
the graph are given in table 4.
20
me./kg
mt./kg
eoo
BOO
*oo%
400
mt./t
mt./l
mt./kg
mt./kg
800
400 -
FIG. 10 Cation replacement diagrams for the herbage of plantain. Initial composition of the solutions in me./l
Na-K
K
Na
Mg
Ca
N03
H2PO4
Ca-K
Na-Ca
Mg-Ca
2.5
2.5
X
2.5
5—x
2.5
2.5
2.5
2.5
5—x
X
2.5
5—x
5—x
5
2.5
2.5
0
5
0.83
2.5
1.67
5
0.83
1.67
2.5
5
0.83
1.67
2.5
X
S0 4
Cl
Period of growth on the treatments: 4 weeks
Renewal of solutions
: 1x
Average yield percontainer
:25 g
X
21
TABLE 4 Vaines of M for the curves in figure 10.
K-Na
K-Ca
•J5 ca
-™mg
¥>
—
—
330
4I0
Mna
325
—
300
-
Ca-Na
Ca-Mg
375
—
_
390
405
370
_
_
average
395
370
315
360
me./kg
me./kg
me./kg
me./kg
These valuesforanycation depend little,ifany, onitspartner ioninthe replacement
series. Therefore, they are averaged to estimate the relative uptake according to
equation (7), with k = 1:a cak = 395/315 = 1.25,a m g k = 370/315 = 1.18, a„ a k =
360/315 = 1.14,and a k k = 315/315 = 1.
There is a slight preference in the order Ca, Mg,Na, K. It maybe that eitherthe
ions compete equally wellwith each other oraretaken upindependently butin such
a waythat their uptakes are linear functions of their concentrations, which arethe
same for allfour ions.
Since concentration experiments with growing plants cannot be interpreted easily,
it is imposable to distinguish between these two processes on the basis of suchexperiments. Butit wasshown already that Rb and Ca ions compete with each other
during theuptake by excised roots of plantain. Nowit is very hard to imagine that
with excised roots two ions compete, but are taken up independently of each other
by growing plants.
If there weretwosystems ofcompetition according toequation (5),forinstanceone
for the combination K-Naand the other for the combination Ca-Mg, then theMg
and Na lines m the K-Ca replacement series would differ considerably from the
horizontal, both m opposite directions (compare section 5.5). Butsince thelinesare
horizontal, it must beconcluded that thefour ions K, Na,MgandCa compete with
each other according to theequations (9)
t/ k = .
tó
**&
+ fcna£na + kmgEmg + kcaEca
.,
*
M
and so on,with about equal values for thecrowding coefficient andfor M.
5.4
O R C H A R D GRASS
The results ofsome replacement serieswith orchard grass aregiven in the figures 11
to 13 The experiments differ in the degree ofexhaustion ofthe treatment solution,
which wasvaried bythe frequency ofrenewal. Roots andstubbles were also harvested
m one experiment. The different response, compared with plantain, is evident from
n t S e r i e S f figUre 1 L T h e K U n e i s c u r v e d
* : JCP
°
"
> the Ca-line is straight
and theNa content increases with decreasing K inthe solution even with a constant
supply ofNa.
22
me. / k g
me. / kg
1200
1200
me. / k g
K 9"
1200
r
800
-.x^Mg
é-
400
^P^§=*--«^—©- o-
,Mg
Ns
0
Ca
©
Mg
O
Ca
No
Na
0
5 *—
Na
K —* 5
0
me./1
0
5 • -
2.5
2.5
Mg
Na
•5
0
K
1200
800 -
400 - Mg
Ca
Mg
2.5
2.5
•
°0
5 »— Ca
2,5
2.5
me./L
«K —*
5
0
me./l
me./kg
me./kg
me./kg
5 ^ -
-•
I
2.5
2.5
"5
°-
1200
800
800 -
400
400
Na
Ca
2.5
2.5
me./l
Na — • 5
0
me./l
0
5
Ca
2.5
2.5
Mg —«• 5
0
me./l
FIG. 11a Cation replacement diagrams for the herbage of orchard grass.Initial composition of the
solutions in me./l
Na-K
Mg-K
Ca-K
Mg-Na
Ca-Na
Ca-Mg
X
K
Na
Mg
Ca
5—x
2.5
2.5
x
2.5
5—x
2.5
x
2.5
2.5
5—x
2.5
x
5—x
2.5
2.5
x
0
5—x
2.5
2.5
x
5—x
NO3
H2PO4
S0 4
Cl
5
2.5
2.5
0
5
0.83
1.67
2.5
5
0.83
2.5
1.67
5
0.83
1.67
2.5
5
0.83
1.67
0
5
0.83
1.67
2.5
Period of regrowth on the treatments: 17days
Renewal of solutions
: 2x
Average yield per container
: 17g
In the Na-Ca series Mg was erroneously omitted.
23
me./kg
1200,-
800 H
/
400,
™
"0
5 *— Na
x
Mg
Na"-»~—•
.
_1_
2.5
2.5
^
K —• 5
O
me./I
"o
5 *— Mg
25
2.5
K —• 5 "o
0
5 « — Ca
me./I
2.5
2.5 '
K —•• S
O
me./I
me./kg
1200 r
800
R^t-==!x>—'
Na
5 _
Mg
25
25
Na
me./I
me.II
F I G . H b Cation replacement diagrams for the whole plants of orchard grass, calculated from the
dry weight and composition of the herbage (figure 11a) and of the roots plus stubbles.Averageyield
of whole plants per contamer: 46 g.
The increasing Na content with decreasing K content shows that these two ions
effect each other in a competitive fashion, independent of the other cations given.
This interaction was studied in detail by BANGE (1959) by means of short time experiments with corn seedlings. He found that the interaction between K and Na is
governed bytwocompetitive systems.Inthefirstsystem K and Na are equallycompetitive, but in the second system the presence of K suppresses the uptake of Na
rather effectively.
Figure 11shows that, apart from where Kisreplaced,the relations between cation
contentandconcentrationinsolutionareverysimilartothoserelationswithplantain.
This suggeststhat here also two competitive systems are operating. Thefirstsystem
is similar to that operating in plantain. The four ions K, Na, Ca and Mg are about
equally competitive. The second system concerns the cations K, Na and probably H
(5.4.2).
24
5.4.1 Thefour-ion system
The contents of the ions Na, Mg and Ca are linear functions of the concentration,
except for the Na content in the replacement series with K (figure 11). Treated according to equation (5) the relative crowding coefficients are therefore about 1and
the uptake relations are then completely characterized by the values of M, given in
table 5.
TABLE 5 Values of M for curves in figure 11.
series
K-Mg
HERBAGE(figure 11a)
A/ca
—
A/mg
270
Mna
—
K-Ca
Na-Mg
Na-Ca
Mg-Ca
270
—
—
—
215
130
200
—
155
275
285 '
—
250
250
140
me./kg
me./kg
me./kg
180
—
—
—
195
155
190
—
160
220
220
—
195
210
160
me./kg
me./kg
me./kg
average
WHOLE PLANTS(figure lib)
Mca
—
Mms
220
Mna
—
It isevident that the values of M depend little on the partner ion in the replacement
series.Therefore, theyareaveraged (table 6)to estimatetherelativeuptake according
to equation (7)with an approximate value of 1for the relative crowding coefficient.
TABLE 6 Relative uptakes calculated from the data of table 5.
herbage
(figure 11a)
Ocana
—
ttmgna
~
CEnana
^
Okna
=
1.8
1.8
1
1
whole plant
(figure lib)
1.2
1.3
1
1 (estimate)
Becausethe uptake of K is mainly governed by the other system there is no similar
wayto calculate atna- The Ca and Mglinesin thereplacement serieswith theseions
at a constant concentration in solution arepractically horizontal,in spite of varying
K concentration andK content. The slopeoftheK curveathigher K concentrations
isnot largerthan theslopeofthe Ca, MgandNa linesinthereplacement serieswith
theseions. Since,moreover, BANGE(1959)provedwithcorntheexistence ofasystem
inwhichK andNacompeteequallywellwitheach other,itisreasonableto conclude
that the relative uptake a^nain thisfour-ion systemisabout 1.
Withexcisedbarleyroots Rb suppressestheuptake ofCa(figure 9),which supports
the supposition ofcompetition between monovalents and divalents.Any competitive
25
effect of Ca on the Rb uptake with this material of course is overshadowed by the
VIETS effect.
Takingintoaccountallavailableinformationitmustbeconcludedthatthefourions,
K, Na, Mgand Cacompete witheach other according to equation (9)
jj
kçgEça,
,»
kkEk + &na-£na + femg-fimg + kc&Eca.
and so on,with about equal valuesfor the crowding coefficients and for M.
5.4.2 The monovalent-ion system
Superimposed on the discussed four-ion system, a system for the K and Na uptake
ispresent.TheK-Nareplacement seriesoffigure 11 showscompetition betweenboth
ions so that the results can be treated according to equation (5). For a correct procedureitisnecessary to substract first the uptake of these ions through the four-ion
system. Since the uptakes through this latter system are relatively small and the
accuracy of the data hardly warrants such a correction, all calculations are done on
the data inthefigure.The constants in equation (5)are given in table 7.
TABLE 7 Values of M, k and a for curves in figure 11.
herbage
(figure 11a)
whole plant
(figure lib)
*
na
800
460
600
370
ATkna
Okna
6
10
6
10
M
M
* e a n d t h e -hole plant, but the
COeffiCientaQdthCrdative U t a k e are
amefor
^i^^i.T?*
?
**
gC8V6Sherea g 0 d indkati0noftheionselectivi of
values f o r t h e f Ï 7
Da
me./kg
me./kg
?
different f 0 r thCh e r b a
the!whokXT
°
*
thMtheKUPtakCWlth
J
Nat
S
S
^
^
s
^
^
^
r
f
b
T
c o m p e ^ ^
this drfference may be dueto hydrogen ion competition
is^nXnendent ofT ^ " * * m ° n ° V a l e n t i m S y S t e m t h e <K + ^ + H) uptake
isindependent of the K/Na rat10 itispossible to transfer equation (9)into
akkEk + a„ ak £ na + H
i7 n a =
Mm
"nak-Ena
a
**E* + ^E^+WMm
Ub =
H
Okk^k + a n ak£na + H
26
( 10)
A/f
Mm
Un isdefined asthe apparent hydrogen ion uptake and is measured by the deficit in
uptake oftheneutral monovalents.Thefactor H characterizesthe competition ofthe
hydrogen ion and is constant possibly because the hydrogen ion concentration is a
constant function of the treatments in the present experiment. The values of the
constantsMmandHcanofcoursedirectlybecalculatedfrom M^andMnaintable7.
They arefor theherbage givenintable 8.
TABLE 8 Values of M, H and a calculated from table 7.
860
4
10
Mm
H
Qkna
me./kg
me./l
The value of H is in the same order as Ens. for £k = 0, but much smaller than
akna• -Ekfor Ena. = 0. This means that the hydrogen ion competes effectively with
the Na ion, but not withthe K ion. Thisisthe sameinthe experiment with orchard
grass offigure5(4.3.1) as can bejudged from the difference between Mt and M na .
Forperennialrye-grassthis difference issmall,indicatingthat aroundneutralpH the
hydrogenion competition withNa isalso small.It willbeshown later that in foxtail
(Alopecuruspratensis) the competition ofthehydrogenissmallcomparedwith K but
largecompared with Na. Apparently, grass speciesdiffer markedly in this respect.
In the experiment offigure5 (4.3.1)aknawas4.4andintheexperimentsoffigure11
itwas 10.Allcalculationsarebasedoninitialconcentrations;thetreatment solutions
were not renewed in the experiments offigure5, but were renewed twice in the experiment offigure11.The difference betweentherelativeuptakein both experiments
isprobably caused bythis difference in degree of exhaustion.
This is confirmed by a calculation ofthe exhaustion, whichispossible on the basis
ofthedatafor thewholeplantsinfigurelib. ThetotalsupplyofKinthetreatments
with0.5me.K/1was 3 X 6 X0.5 = 9me.K, the plantweightwas46grams and the
contentwas380atEt = 0and600me.K/kgat£ k= 0.5me.K/l,sothattheuptakewas
about 10me. K. Hence at this supply, exhaustion was complete and the K content
would havebeen higher if the supply had been increased bymore frequent renewal.
An experiment with practically daily renewal of the treatment solutions is given in
figure12.The relevant constants are given in table 9together withthose of the two
other experiments.
TABLE 9 The effect of exhaustion on k and a.
figure
11a (herbage) 12a
£k + £na
renewal sol.
£kna
akna
5
0
2.5
4.4
5 5
22
66
1010
5 5
12 12
2020
3333
12b
3.3
12
15
23
me./l
27
m«./kg
1200h
me./kg
t
1200H
,'o
eoo
<00h
«00
+-®^-_®___
x
X
x
®"
®
®
®
-X-J
\Na
Na
2.5
2.5
• 5
0
me./l
FIG. 12 K-Na replacement diagrams for the herbage of orchard
solutions in me./l
K
Na
Mg
Ca
N03
H2PO4
S0 4
Cl
a
x
5—x
2.5
2.5
5
2.5
2.5
0
grass. Initial composition of the
x
3.331.67
0.17
3.33
0.17
1.67
0
Period of regrowth on the treatments: 18days
Renewal of solutions
: 12x
Average yield per container
a : 12g
b :12g
raPldly With deCreasin d e e e
tlat vÏthont anvna I T
* ^ ofexhaustion so
005mKnZ f Tnl^T* b e a t 1CaSt 5 °- T h i s m e a n s t h a * even with
0.05 me. K 1 and 5me. Na/1 the K/Na ratio of the uptake through this monovalent
xonsystemis still about 0.5. Hence Na uptake through this system
ToclZo^
the K supplyispracticallyexhausted.TheNainplantsgrownwithout exhaustion of
K is mainlytaken up through the unselective four-ion system
Plants differ markedly with respect to this uptake system for monovalents. It is
28
absent in plantain to such a degree that it cannot be detected in replacement series
withgrowingplants.TheNauptakeisaffected toadifferent extentbytheH+concentration with orchard grass, perennial rye-grass and foxtail. With corn the Na in the
tops taken up through this system is negligible (compare WYBENGA, 1957)and data
of SUTCLIFFE(1956, 1957)infigure 13 showthat slicesofpotatoesandbeettissuealso
differ considerably in thisrespect.
mi.M
me./I
FIG. 13 K-Na replacement diagrams for washedbeetdisks(a),potato disks(b)andredbeetdisks(c)
Composition of the solutions in me./l: K :x, Na :20—x, CI :20.
Period ofuptake a: 2-40hours; b:2-70 hours; c:2-12 hours.Thesolutions wererenewed frequently
enough to prevent severe exhaustion. Data of SUTCLIFFE (1956, 1957).
5.4.3 Interaction between both systems
The rather independent operation of the four-ion and monovalent-ion system is
particularly clear in the K-Ca and K-Mg replacement series of figure 11, where the
Ca and Mguptake lines are not affected by the widely varying uptakes through the
monovalent ion system. It will be shown later that this does not hold where yield
responses occur.
5.5
A N I O N UPTAKE BY PERENNIAL RYE-GRASS
Anexperimentwithperennialrye-grass,incorporating allpossiblereplacement series
between NO3-, H2PO4-, CI"and SO4-- was carried out. Where NO3is one of the
replaced ions, particular care must be taken that the growth is not affected by N
shortage.For thisreason thesmallestconcentration ofNusedwas2.5me./l. Further
29
details on the composition of the treatment solutions are given in the caption of
figure14.
TheuptakeofH2PO4andSO4increasesonlyslightlywiththeexternalconcentration,
within the range studied, but the NO3uptake and CIuptake increase considerably
withincreasingconcentrations.SincethelinesforbothionsintheNO3-CIreplacement
series areabout straight, any conclusion as to the competitive nature of the relation
mi./kg
me./kg
meVkg
1000
1000
/N-1!
"V.0<
S00
N,.
^ o
0—s 2 *- 0 '
©—Ô—©—S>—Ô
I
0
10
5
N
»10
5
• ct
0
J_
S
0
10 . . — S
5
me./l
mt./kg
I
N
• 10
0
m«./l
S
"0
10
P
N
• «
0
S
mt./l
mt./kg
m«./ kg
1000
1000
JJ-1500
X
1000
N -1500
_ X
•*X\N-1500
x
x
»
,o^°
0
n
_1_
5
P
S
Cl
«-10
0
""•"
30
n
0
500
.0«=®-^
s——
10 —
o
CL
500
S
J_
0
10 _
5
S
Çt
5
m»ji
,.10
0
1° _
1
s
s
5
p
i»
0
m,,n
cannot bemade.Butin the NO3-Sand the NO3-Preplacement seriesthe CIcontent
decreaseswithincreasingNO3in solution, eventhoughthe supply of CIisconstant.
A similar effect on the N-content is noted in the Cl-P and Cl-S replacement series.
Here,thescatteringmaybeduetoincompleterecoveryoftheNO3withthe Kjeldahl
modification used at that time, but the decreasein N content was also observed in
othersimilarexperiments.Someexperiments,discussedlater,showthatthedepressing
effect on the N uptake manifests itself also in the NO3content. Unfortunately, the
samplesofthisexperimentwerediscardedbefore theimportanceofanNO3 determination wasrealized.
The data suggest the existence of a competitive interaction between NO3 and CI
during the uptake by growing perennial rye-grass. This conclusion is supported by
dataof LUNDEGÂRDH(1959)onshorttimeexperimentswithwheatplants.Heshowed
that theNO3and CIionsin solutiondepresseachother'suptakeconsiderably.
FIG. 14 Anion replacement diagramsfor the herbage of perennial rye-grass.Initial composition of
the solution in me.per 6liter
Cl-N
No3
H2P04
S04
CI
K
Na
Mg
Ca
S-N
P-N
P-Cl
S-Cl
S-P
X
X
X
5
4
4
(10-x)
4
(10-x)
4
(10-x)
4
4
X
5
5
5
(10-x)
5
(10-x)
X
(10-x)
x
15.5
0
1
1.5
15.5
0
1
1.5
10
5
2.5
2.5
10
5
2.5
2.5
15.5
0
1
1.5
5
10
5
2.5
2.5
Period of regrowth on the treatments: 12days
Renewal of solutions
: 1x
Averageyield per container
: 15g
TheNcontentswerebroughtwithinthescaleofthegraphsbysubstracting 1500me./kg;thescattering
of the observations isabsolutely correct but seemsrelatively too large.
31
6 REGULATION OF THE (C-A) CONTENT
6.1
SUMMARY
Theeffect ofsimultaneouslyvaryingthecationandanionsupplyontheioniccontents
isstudied under conditionswheretheyielddoesnot vary appreciably withthe treatments. Although there are large variations in the C and A contents, the (C—A)
content appearsto beaconstantfunction ofthenutrient supply.Depending onconditions,its constant valueisfound between 900and 1100me./kgfor grasses.Taking
intoaccountthelargevariationoftheorganicanioncontentinexcisedroots following
salt treatments, this indicates that growingplants can regulate their (C—A) content
at a constant value(compare 3.4)at varyingcation and anion uptake.
6.2
EXPERIMENTS
6.2.1 Cation replacement
Theanionandcationcontents oftheherbagegrown ontheK-Ca and K-Mgreplacement series offigure11aregiveninfigure15.
The constancy ofthe A content overthegreaterpart ofthereplacement rangemay
me./kg
2000
Ç
-•—
0
O
•
0
C-A
1000
_o
«
' _ ..
Co(Mg)
Ô
0-7-
- Ô —
1
2.S
2.5
mt./l
FIG. 15 TheC, A and the(C—A) contentsoftheherbagegrown ontheK-Ca(o)and K-Mg(•)
replacement series,presentedinfigure11.
32
be readily related to the constancy of the anion supply, but it is not clear why the
totalcationcontent doesnotincreasewiththeincreaseofthereadilyabsorbed cation
in solution. The reason may be either that the uptake rate of the cations is at its
maximum as far as its absorption mechanism is concerned or that plants grow in
sucha waythat the (C—A) content isregulated at a constant valuewhen cations are
adequately supplied. The two possibilities may be distinguished by experiments with
varying cation and anion supply.
6.2.2 Nitratefertilization
SAID (1959) applied 0, 10, 20, 30 and 40 me. of K-, Na-, Mg- or Ca-nitrate to soil
filled potsplanted withperennial rye-grass or orchard grass.The cation status of the
soil was such that the yields were not affected by the cation supply. Nitrate in the
unfertilized potswassohighthat thenitrogenfertilization increasedtheyield onlyby
a little over 10%.
The fertilization affected the contents to a large extent as is illustrated in table
10where contents at 0 me. and 40 me. nitrates per pot are given for both grass
species.
Thetotalcationcontent of both perennial rye-grass and orchard grass is practically
independent of the cation given with the nitrate ion although the contents of the
individual cations differ considerably. With both species the contents of ions taken
upascationsandasanionsincreasewithincreasingnitratefertilization.Withperennial
rye-grass, the uptake ratio of cations to anions decreases from about 0.65 to about
0.51withincreasingnitrate fertilization, butthisratio remains constantatabout 0.60
with orchard grass (SAID, 1959). This difference between the grass species makes it
difficult to generalize alonglinesofcationequivalent constancy and constancy ofthe
uptake ratio of cations to anions.
Nitratewasdeterminedandfrom organicNandtotalStheinorganicSO.j~~content
can be calculated. Hence it is possible to calculate the inorganic anion content (A)
(2.3) and to relate this value to the total cation content (C). This is shown for all
treatments and both plant species in figure 16.The A content appears to vary from
600to about 1100me./kg and the C content from about 1600to 2100 me./kg. The
difference between the cation content and anion content is constant at 1000me./kg
for both species, throughout the whole range. This constancy is strikingly different
from theresultswithexcisedroots asshowninfigure3,anditindicatesthat growing
plantsregulatethe(C—A)contentwithinarathernarrowrange,wherepossible.This
range is the same for orchard grass and perennial rye-grass, even though there is a
difference betweentheuptakeratio ofcationsto anionsfor both species.The organic
N content without nitrogen fertilization is 1850 and with nitrogen fertilization
2200-2600 me./kg. The internal HCO3- production due the metabolic reduction of
nitrate was,therefore, about 1850and 2400me./kg,but the(C—A)contentisinboth
casses about 1000 me./kg, which indicates that the organic anion content is not
directly dependent on the nitrate metabolism.
33
o
g
ca s M
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*Ti <S CJ —I *H
111
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34
o
ei (S r- N m
co co CN co TJ-
1000
itie./kg A
Flo.16 TheCandAcontentsoftheherbageoforchardgrassandofperennialrye-grassfertilized
with0,10, 20,30 or40me. nitrateastheK,Na, MgorCasalt.Fromdataof SAID (1959).
nie.f
8 day«
2000
•2V
•jS^
40days
1000
»
^
^ s ^
.^-""^
M
• HOmg N
o 560mgN
n
500
mi./kg
1000
A
50
100
anion uptak» m*.
FIG. 17 a.The CandA content oftheherbageofperennialrye-grassharvested between 8and40
daysafter application of10 and40me.asNH4NO3.
b.Theuptakeofcationsandanionsintheherbagefrom8to40daysafterapplicationofthenitrogen.
Fromdataof DIJKSHOORN(1958).
35
6.2.3 Periodic harvests
DIJKSHOORN(1958b)harvested perennial rye-grass on soilwith 140and 560mgN as
NH4NO3 at four-day intervals from 8 to 40 days after the beginning of regrowth.
Sincetheconditionswerefavorable for nitrification, thiswascomparable to a nitrate
fertilization. Theanionuptakeisplotted againstthecationuptake for the 140mg N
treatment infigure17b.
With the firstfiveharvests the anion uptake is considerably higher than the cation
uptake. The ratio between cation uptake and anion uptake of 0.5 is maintained as
long as the nitrate is not exhausted. After the fifth harvest the nitrate is exhausted
andthecationuptakeproceedswithoutconcurrentanionuptake.Thesedataillustrate
that there is no direct coupling between cation and anion uptake.
The Cand A contents for both treatments are plotted infigure17a.The A content
decreases with timebecause ofnitrate exhaustion and because of dilution by growth
ofanions suchasCl - (DIJKSHOORN, 1958a).Evenwiththislargechangein A content
the(C—A)changedonlyfrom 925 to 1050 me./kg.Although theratiobetween cation
andanionuptakevariedconsiderablyduringgrowth,theplantsmaintained aconstant
(C—A) content during the period of 40 days.Thewatercontent ofthe fresh herbage
was600per cent at the 8th dayand 375per cent of the drymaterial at the 40th day.
Hence, the (C—A) content variesconsiderably when expressed on a fresh weight or
waterbasis.
6.2.4 Periodicharvests at two temperatures
DIJKSHOORNand't HART(1957)studied theeffect oftemperature onthe composition
ofperennialrye-grass.Onesetofplantsgrewat 20°Cfor 11 daysandat 10°Cthereafter; the other set grew at 10°Cfor 11days and at 20°Cthereafter. Samples were
Cation uptake
me.
c
ma./Kg
* * 2000
J**
^.1:1
1000
• 10-»20»C
x 20-»10»C
500
-J
1000
I
1500
me,/kg A
40
60
Anion uptake me.
FIG. 18 a. The Cand A content of the herbage of perennial rye-grass, harvested between 0 and 20
days after transfer from 10to 20 and from 20 to 10 centigrades.
b. The uptake of cations and anions in the herbage from 0 to 20 days after the transfer
From data of DIJKSHOORN and 'T HART (1957), and not published data on nitrate.
36
taken from 2 to 20 days after the transfer. The final yields were 13 g/pot for the
10° ->20°plants and 11g/pot for the 20° -*10°plants.
Theanion uptake isplotted against thecation uptake infigure18b.The ratio is0.4
for the 20° ->10°plants and 0.6for the 10° -»20°plants.The Cand A contents are
plotted against each other in figure 18a. The A content of the 10° ^-20° plants increases and that of the 20° ->10° plants decreases during the periods of sampling,
which indicates the different effect of temperature on growth and uptake. However,
inbothcasesthe(C—A)contentremainscloselyat 900me./kg,whichagain indicates
regulation of the (C—A) content. The water content varied according to treatment
and date ofharvesting between 750and 550per cent of the dry material.
6.3
DISCUSSION
The(C—A) content ofgrassin thegreenhouseexperimentswasfound to be constant
at the values of table 11.
TABLE 11 (C—A) contents in four experiments.
figure
grass
root med.
year of exp.
temp. (°C)
(C—A) me./kg
15
16
17
18
orchard
water
1960
20-25
1100
orchard per. ryesoil
1958
20-25
1000
1000
per. ryesoil
1956
20-25
950
per. ryesoil
1956
20
10
900
900
The values are strikingly close together in spite oflarge treatment differences and in
the same range as the (C—A) content of blue grass and wheat in the experiment of
PIERCE and APPLEMAN (fig. 4). In short time experiments similar salt treatments as
givenhereaffect the(C—A)content ofplantmaterialconsiderably(section2).Hence,
the resultscan onlybeunderstood bysupposing that thesetwograssspeciesregulate
the(C—A)contentatanormalvalueroughlyintherangebetween1100and900me./kg
during their growth.
Sincethe(C—A)contentequalstheorganicanioncontent,(fig.4a)suchplantshave
a neutral reaction (pH x 6).Accordingly, the organic anions can accumulate in the
shoot in the following ways. Organic anions formed in the roots are translocated
upwards as their salts, or the nitrate ion is translocated as its salt, and metabolized
intheshootintoorganicNandorganicanion.
An upward translocation of bicarbonates (HC03~ + metallic cations) or a downward translocation of acids (inorganic or organic anions + H+) cannot contribute
substantially to the organic anions in the shoot, since buffering substances (mainly
phosphates) capable of buffering at pH 6arecommonlypresentatabout 100me./kg
only,while (C—A)isabout 1000me./kg or more.
37
Therefore, a regulation of the organic anion or (C—A) content is possible only if
sufficient organicanions andnitratemoveupwards astheir salts,and organic anions
in excess of about 1000me./kg(in the case of grass) move downward as their salts.
Subsequently, decarboxylation takes placeinthe roots and the HC03 - produced exchanges with an anion from a neutral salt in the medium. Obviously, this kind of
regulation fails when either the uptake of cations is too small or the uptake of inorganic anions which stay as suchin the plant istoo large. It may fail as wellwhen
metabolic reduction of nitrate proceeds at a low rate in the shoot. These conditions
did not existin the experiments ofthe present section, asisevident from the normal
values for the (C—A) content ofthe plants. Their study requires other experiments
with more extreme treatments, including those resulting in reduced plant growth as
a result of stress on theion balance.
38
7 IONIC BALANCE AND GROWTH OF BARLEY
7.1
SUMMARY
The relation between nutrient supply, composition and yield in barleyisdiscussed.
Itisshownthat, apartfrom anyspecificshortageofsingleions,astressonthe (C—Ä)
content leadsto a reduction of theyield.
Theeffects ofareplacement of KbyCa, of CIexcessand of Na and N fertilization
are considered particularly.
7.2
DESIGN OF THE EXPERIMENT AND YIELDS
Tento twelvebarleyplants weregrownin potscontaining8.5lbs of Evesboro sandy
loamandharvestedatthetimeofearemergence.Aninitialnitratesupplyof30me./pot
appeared to be adequate.
With Ca, Mg and possibly Na-nitrate, K was in short supply. K can be supplied
by(1)replacing the Ca, Mg or Na cation in the nitrate by K, (2)adding K2SO4and
(3)adding KCl. Sincethe exchangecapacity ofthe soilisabout 250me./pot and the
pH about 6, a treatment with KHCO3results in a soilwith a reasonable K content
withoutanincreased anioncontentandgivesnomoreinformation than,for instance,
the experiment offigure17.
To restrict the number of treatments without losing the possibility of comparing
results in terms of replacement series,the K salts wereadded in amounts equivalent
to the nitrate.
Hence thetreatments were:
1. xme.KN0 3 + (30—x)me.Ca(N03)2 withx = 0, 7.5, 15,22.5and 30
2. xme.KN0 3 + (30—x)me.NaN0 3 withx = 0, 15and 30
3. xme.KNOs + (30—x)me.Mg(N03)2withx = 0, 15and 30
4. xme.NaN0 3 + (30—x)me.Ca(N03)2 withx = 0, 15and 30
5. xme.NaN0 3 + (30—x)me.Mg(N03)2withx = 0, 15and 30
6. xme.Ca(N03)2 + (30—x)me.Mg(N03)2 withx = 0, 15and 30
Totesttheeffects ofadditional salts,KCl, K2SO4and CaCl2wereaddedin amounts
of 30me./pot to the K-Ca replacement series.The nitrates of the four cations were
alsousedin amounts of 10and 20me./pot to study the effect of nitrate application.
For salt damage the treatment 30me.N0 3 + 30me.Cl is most critical. It will be
shown later that one of the main difficulties involved in heavy fertilization of poor
soilsisrelated to thiscombination. The soilreceiveda liberalamount ofCa and Mg
39
phosphate. The experiment was made in triplicate and harvested at the time of ear
emergence.
• KstCa
X K«£Co +30me.K2S04
O K;»Co +30m«.CaCl2
+ K;±Ca+30mt.KCt
20
10
me,Ca(N03)2
FIG. 19 Pot experiment with barley. The yield diagram.
TheyieldsoftheK-Catreatments aresummarizedinfigure19.Ontheleft the effect
of the KN0 3 and on the right the effect of the Ca(N03)2 application is presented.
Themiddlepart givestheeffect oftheK-Ca replacementwithand without additional
salts.
Anitratesupplyof30me./pot isapparentlysufficient. ThetreatmentwithCa-nitrate
yielded about half asmuch asthetreatment with K-nitrate, whichindicates a severe
K-shortage.TheK-Careplacementseriesshowsthat 15me.KN0 3 + 15me.Ca(N03>2
suppliessufficient K.TheKshortagewasrelievedbytheapplicationof30me.K2S04.
TheyieldoftheKNO3+ K2SO4treatmentishigherthanthatoftheKNO3treatment,
but this wasinreproducable (comparefigure29).TheK shortagewasnot relievedby
the application of KCl; the treatment KNO3 + KCl even gave a much lower yield
than KNO3only.
7.3
IONIC INTERRELATIONS
7.3.1 Potassium-Calcium-replacement
The cation contents of the K-Ca replacement series are given infigure20a. The K
and Calinesarecurvedin opposite directionsandwithdecreasing Kthe Mgcontent
increases in spite of the constant Mg supply. The shape of the curves suggests that
all the K is taken up in competition with Ca and Mg. However, it has been shown
(5.4, figure 11) that only a minor fraction of the K is taken up through a system
40
where the four cations compete and the major fraction enters the plant through a
system operative for the K and Na ions.
mi./kg
mt./kg
«30m«.K2SOJ
2000 o
.
(C-A)
1000
Mg
U°-*--&--*---•
0
30.
• 30
0
0
30.
K.
mt.
30
0
FIG. 20 Pot experiment with barley. K-Ca replacement series at an anion supply of 30me.NOs
a. in the absence of K2SO4
b.in the presence of K2SO4
c.the C,A and (C—A) content of the seriesin absence of K2SO4.
The difference between the experiments offigure20andfigure11doesnot concern
the competitive system, but the yield response.The yield wasnot affected in theexperimentoffigure11,butinthepresentexperimenttheyielddecreasedwithdecreasing
K content.
Suppose that with K the upward transport of (C—A) is 100me. per day. This is
sufficient to maintain a (C—A)content of 1000me./kgat a growthrate of 100grams
per day. However, without K an upward transport of for instance, 50 me. (C—A)
perdaymaintainsa(C—A)content of 1000me./kgat agrowthrateofonly50grams
per day.
Hence, when a plant responds to a stress on the (C—A) content with a decrease in
growth rate, this counteracts any sharp decrease in the (C—A) content and leads to
an enhanced content of Ca and Mg. The yield reaction (figure 19)is therefore the
reason that the (C—A) content decreases only from 1200 to 900 me./kg with the
replacement ofK by Ca (figure20c).
By adding K2SO4 the K content is higher over the whole range of the K-Ca replacement series (figure 20a and b). Since little SO4 is absorbed, the stress on the
(C—-A)content isrelieved. TheA content increased from 800to 950me./kg, but the
C content increased from 1710to 2230 me./kg ,so that the (C—A) content was increased from 910 to 1280 me./kg by K2SO4 in addition to Ca nitrate. The yield
depression isof course absent after fertilization with K2SO4.The (C—A) content of
41
theKNO3+ K2SO4treatmentsis2220—880= 1340me./kgandonlyslightlyhigher
thenthe(C—A)contentof 1250me./kgfortheKNO3treatment.Thisagainillustrates
plant regulation ofthe(C—A) content.
7.3.2 Application ofchlorides
Theaboveinterpretationimpliesthat,apartfrom specificfunctions, cationsarenecessarytokeepthe(C—A)contentandtherebytheorganicanioncontentattheirnormal
levels. RATHJE (1952) suggested thisfunction of the cations, especially of the K ion.
Hearrivedatthisbecauseyeastundertheinfluence ofsugar,andLemnaand Chlorella
under the influence oflight take up K ions and excrete CIions, this situation being
reversedwithexhaustion ofsugar orwithdarkness.Thischange oftheinorganicion
content has to go together with a change of the organic anion content, because
neutralityismaintained. Sinceitisnotpossibletofindspecificfunctions for K atthe
ratherhighcontentsinvolved, RATHJEsuggestedthatthiscationisnecessaryinrather
high concentrations because the organic anions are necessary for maintaining good
growth.
me./kg
me./kg
20001-
2000
1000$-
1000
(C-A)
60.«—Ca
FIG.21 Potexperimentwithbarley.
a.TheK-Careplacementdiagramat 30me.NOaplus30me.Cl.
b.TheC, Aand(C—A)content.
Any cation accompanied by aninorganic anion is uselessin this respect, sothat it
is difficult to relieve a stress onthe (C—A) content by the application of a fertilizer
containing an anion that is readily absorbed and stays as such in the plant. This is
illustratedbytheresultsofthetreatmentswithadditionalKClandCaCl2,summarized
42
as a K-Ca replacement series over a range of 60 me./pot in figures 21a and b. The
anions were 30me.NOs" and 30 m e . Q The Mg line is practically horizontal and the Ca line is straight except for the
treatments 0 and 7.5 me.K. Since only these treatments have a lower yield than the
other treatments with CI (figure 19),this reaction of Mg and Ca is directly related to
the yield response, as in figure 20.
With increasing K the C content increases (figure 21b). This is not associated with
an increase of the (C—A) content but with an increase of the A content. Rather than
relieving the stress on the (C—A) content, as with K2SO4, the KCl application increases the CI content from 820 me./kg at 0 me.K to 1390 me./kg at 60 me.K. The
(C—A) content is maintained at the low level of 660me./kg, and this is accompanied
by a considerable yield reduction. It should be noted that this does not imply that the
stress on the (C—A) content is the only cause of yield reduction. Osmotic stresses in
the soil due to Q - and NO3" application may have interfered as well (compare 8.7).
7.3.3 Fertilization with sodium
The element K has apparently two functions in the plant. It is essential as such and
it functions as a positive charge accompanying organic anions, necessary for growth.
As an essential element K cannot be replaced by any other ion. According to
LUNDEGÂRDH (1951) severe K deficiency develops at a level of about 200 me./kg.
With a good supply of Na it is even possible to obtain small grain plants with a K
content as low as 100 me./kg (BROESHART and VAN SCHOUWENBURG, 1961). These
observations indicate that the minimum and essential level of K in small grains and
grasses is between 100 and 200 me./kg.
The cations K, Na, Mg and Ca all function as positive charges. The Na ion is the
most important for grasses and small grains grown at a low K level, because it can
be taken up readily. For plant species such as plantain (5.3) the Ca and Mgions may
do as well in this respect. These two functions of K and the role of Na will be illustrated by means of the K-Na and the Ca(Mg)-Na replacement series of figure 22.
A comparison of the Na-nitrate and Ca(Mg)-nitrate treatments in figure 22b and c
show that for both the (C—A) content is about 900 me./kg, the yield 3.5 g/pot, and
the K content about 200 me./kg. This K content is about the minimum, so that the
yield in both cases was mainly determined by the amount of K which was taken up.
The ability of the plant to take up Na more readily than Ca(Mg) is reflected by the C
content of 2300 me./kg for the Na treatment and 1650 me./kg for the Ca(Mg) treatment. But this high C content is accompanied not by a high (C—A) content, but by
a highA content aswith the CItreatments (figure 21).The highA content is of course
not a result of the high CI, but of the high nitrate content which increased from 430
to 980 me./kg by replacing Ca(Mg) with Na. This inability to regulate at a high Na
and a low K level will be studied in more detail in section 8.3.
The difference in the ionic balance of K deficient plants at high and low Na is reflected in their appearance. The plants with Ca(Mg) nitrate were stunted with a dry
43
matter content of 15 percent, but developed normally otherwise.TheplantswithNa
nitrate werelongleaved and weakwith a dry matter content of 12per cent and had
many more tillers. These two symptoms of K deficiency are described by WALLACE
(1944).Apparently, theonlyeffect ofreplacing Ca(Mg)nitrate withNa nitrateisthat
the plants change from one form of K deficiency to the other, and it can hardly be
concludedfrom thispartoftheexperimentthatNacanreplaceKasapositivecharge.
However,thetreatmentwith 15me.Ca(Mg)nitrate + 15Nanitrateyielded6.5g/pot,
and theplants had a (C—A) content of 1150me./kg. Both werehigh compared with
the3.5g/potandthe900me./kgfortheNa-nitrateandtheCa(Mg)nitratetreatments.
But the K-content wasalso at its minimum of 200me./kg, so that K as an essential
element wasstilllimitingtheyield.The remarkable difference isthat on pots treated
withtheNa nitrate orwith Ca(Mg)nitrate,theplants accumulated (200/1000) 3.5 =
0.7 me.K, whereas theyaccumulated (200/1000) 6.5 = 1.3 me.K on the pots treated
with a mixture ofboth nitrate forms.
mt./kg
2000A-
me./kg
2000
1000 h
meNO, Ï Ü ^ T T r ? fyi ^ K ' N a (a) a n d Ca(Mg>Na(b)replacementseries at30
S ™ h n , ^ ™
, ? d^V**** a r e 8ivon i n fisure c a n d d- ™e Ca-N* a n d M S" Na
seriesgaveaboutthesameresults,sothatbothareaveragedtoaCa(Mg)-Naseries.
Probably, the exploration of the soil in the pots treated with Ca(Mg) nitrate was
hampered by the stunted growth and on the pots with Na-nitrate by the severe
competitionof Na withK (5.4). Inthepotstreatedwiththe mixture of Ca(Mg) and
Na nitrate theuptake ofK wastwiceaslargebecausetheexploration for K wasnot
hampered by stunted growth dueto stress on the (C-A) content and not to such a
largeextentbycompetition ofNawithK. Thisprovesindeed that Na mayreplaceK
as a positive charge.
44
The cations K, Na, Mgand Ca are readily taken up byplantain (5.3). Preliminary
experiments with this plant species showed that under conditions where grass yields
are depressed becauseofK shortage, plantain grows normally.
7.3.4 Fertilization with nitrogen
Theioniccontents and theyields ofthetreatments 0,10, 20and 30me.nitrate asits
K orCa salt are giveninfigure23.
mt./kg
b
mt./kg
y
/
a
/
K-farln
1
1
1
3000
3000
-
'n-or 9 .
/
i
(>**-—•**°
2000
2000
»
,\
\
\
1000 h
•
C/
\
/
S
\\
•
n
0
me./kg
1
A ^'S
~s
0
?' " ^
) \ 9
yto
'*^*^^*s*— X
""-•—'of*—
0
<
<
,^
1
:
k*.
\
•
M
-Ü2—
Trt10
—o—
1
20
30
mt.Ca(N03)2
FIG. 23 Potexperiment with barley. The KNO3 (a)andCa(N03>2 (b) concentration series. The
(C—A) contents, the NO3content and the yield are giveninfigurecandd.
TheunfertilizedplantswereverystuntedandtheCandAcontentswerehighbecause
oftheabsenceofanydilutionbygrowth.Thenitratecontentwaslowandbadgrowth
wasinthefirstplaceduetonitrogenshortage.The(C—A)contentwasonly900me./kg,
probably because at this lowsupply anynitrate absorbed is metabolized in the
roots.Thegrowthwasstunted from thebeginning, whichindicatesthat the stress on
the(C—A)contentexistedfrom thebeginning.Forthisreason,smallcellsare formed
whichhaveahighnitrogen content in spite ofthenitrogen shortage.
With 10me.KN03thegrowthappeared tobethesameaswith30me.KN03 during
the first part ofthe growth period, but later on the growth was retarded becauseof
nitrogen shortage, asjudged from the low NO3content and an Nand Kuptakeof
45
9me.and 4me.,respectively, from a supply of 10me.The (C—A) content wasonly
900me./kgprobably because oftheabsence ofnitratereductionin theleaves during
thelaterpart ofthegrowingperiod.Duringthefirstpartgrowthproceeded normally
and a normal (C—A) content was probably maintained. At this stage plants with
normal sized cells of a normal protein content were formed. The transition from
higher to lower N content as the result of N application at low N levels has been
frequently observed.
With 10me.Ca(N03)2the N-uptake was only 6.5 me. and the plants were stunted
because of severe K shortage, as appears from the low K content and the very low
(C—A) content. Withincreasing Ca(NC>3)2 theyieldincreased because somemoreK
became available. This may be due to exchange reactions between the soil and the
soil solution.
7.4 (C—A) CONTENT AND YIELD
TheCandAcontentsoftheplantsofalltreatmentsaregiveninfigure24.Thenormal
value of the (C—A) content is apparently somewhat higher than in grasses (section
6.3) at around 1250 me./kg, although many treatments resulted in lower (C—A)
contents.
1000
2000
m«./kg A
Fio. 24 Pot experiment with barley. The relation between the Cand A contentsfor alltreatments.
The (C—A) contents and the yields are related as shown infigure25.It could be
that lowyieldsareassociated withalowwatercontent oftheplants and,becausethe
ionsaremainlyintheplantjuice,alsowithalow(C—A)content.However,thewater
46
content ofplants withayieldof9gramsper pot was675percent and ofplants with
3gramsyieldwas525percent ofthedrymaterial, whereas (C—A) varied from 1200
to 600me./kgwithin the sameyieldrange.
yield
9
10
• • •
•
500
••
1000
mt./kg (C-A)
FIG.25 Potexperimentwithbarley. Theyieldandthe(C—A)contentforalltreatments.
Therefore,therelationbetween(C—A)andyieldmustbeunderstoodinanotherway.
Either,thetreatment affects theyieldand theyieldaffects the(C—A) content, or the
treatment results in a stress on the (C—A) content and this stress affects the yield.
Experiments with more extreme treatments are required to distinguish between both
views. If, in addition, it is only possible to combine a high yield and a low (C—A)
content, a highyieldisone ofthe conditionsfor anormal (C—A)content. However,
ifinadditionitisonlypossibletocombinealowyieldwithnormal(C—A),anormal
(C—A) content isoneofthe conditions for a highyield.
47
8 F U R T H E R EXPERTIMENTS OF THE
RELATION BETWEEN N U T R I E N T SUPPLY,
(C-A) CONTENT AND YIELD
8.1
SUMMARY
A distinction is made between the effect of the nutrient status of the plant on the
growth rate and the correlation between nutrient status and yield.
Subsequently it isshownthat a normal (C—A) content isone of the conditions for
maximalgrowth. Nafertilization, CIapplication and therelation between NH4fertilization, (C—A) content and yield isconsidered morein detail.
8.2
NUTRIENT STATUS, GROWTH AND YIELD
At the time of sampling, a functional relation may exist between the nutrient status
and the growth rate of a plant. But the relation between the nutrient status and the
yield at the time of sampling is, at most correlative, because the yield is the growth
rate integrated overthewholegrowingperiod.
Infigure26,three growthcurvesaregiven on an arbitrary scale.Itissupposed that
the growing conditions are constant functions of time. Curve A represents the yield
on afieldwith a plant species with a normal growth. During the early part of the
growing period, new assimilatory products are used to form new leaves and these
leaves contribute to light utilization. Hence, the growth curve is more or less exponential. At a certain stage,hereat the weight 5and time 3.3,all the light is intercepted, i.e. the crop surface is closed. Thenceforth the yield increases linearly with
time,untilrespirationallossesorsenescencebeginstointerfere. Thesmallertheplant
density,thelatertheonsetofthestraightlinepart ofthecurve.Singlegrowingplants
mayshowa similarstraight lineportion whena stageisreached without net increase
ofleaf area.
Curve Brepresents the growth of a crop of a plant species with a net assimilation
rate at one-half of the net assimilation rate of the plants A and, at the onset of this
difference (time 0), of the same size. Because plants B assimilate at a much slower
rate,a difference in sizedevelopsrather quickly sothat at thetime 5.7instead of 3.3,
the closed crop surface is established. After that the growth rate of crop Bdoesnot
change with time and is only one-half of the growth rate of crop A. The yields of
B and A will be near to this proportion as long as senescence, etc. do not disturb
growth. Hence,inthiscase,theultimate ratio oftheyieldscorresponds quite wellto
the ratio ofthe growth rates.
48
In the case of plant species C and A, the growth rate of Cisagain one-half of that
of A, but now because for each gram of dry matter produced only half of the leaf
surface is formed. At the beginning the weight increase of plants A and C is about
the same because the leaves present at time 0 assimilate at the same rate. However,
plants C staybehind in due course because lessleaf areaisformed. Theweight of 5
units isreached at time 4.3.Atthis timecrop A,having a yield ofabout 10,already
hasaclosedcropsurface. CropCisstillopenbecauseoftheretardedleaf formation,
totol
dry matter
FIG. 26 Three growth curves.
and this crop proceeds therefore to grow in a more or lessexponential fashion and
catches up with crop A. Around time 6, also crop C intercepts all the light and
from then on both crops grow at the same linear rate, because the net assimilation
rate is the same. The difference in dry matter production of about 6 units remains
unchanged but the relative difference decreases very rapidly with time. Hence, only
ataroundtime4istheyieldratio aboutequaltotheratio ofthegrowthrates,whilst
before and thereafter the yieldratio ismuch lower. In this case the yield differences
reflect the growth differences only,if the onset of the growthdifference occursin an
earlystageandifthecropisharvested attheendoftheperiodofexponentialgrowth.
WATSON (1952) studied the effect of nutrients on growth by growth analysis. He
found that aneffect ofnutrientsmanifests itselffirst intheleaf development and that
the net assimilation rateis onlyaffected in cases of more extreme growth reduction.
This conclusion was confirmed by DEWIT(1958) in a study on the effect of the
49
nutrient status of plants on the transpiration ratio. Therefore, the effect of nutrients
on the growth of a crop is better pictured by the growth curves C and A, than by
the curves Band A offigure26.
Fertilizer experiments withthe purpose of relating nutrient status and growth rates
onthebasisofyieldsmusttherefore becarried outwithplantsgrowingexponentially.
On the other hand, densily planted grass with a high leaf density on a reasonably
fertile soil and grown for some weeks very likely shows small yield effects of treatments(10.2).
8.3
SHORTAGE OF MICROELEMENTS
The low (C—A) contents offigure25may result from bad growth, or bad growth
from a stress on the (C—A) content (7.4).Apparently, varying the supply ofmacronutrients isnot a suitable method for distinguishing between both possibilities. But,
growth may also be varied by varying the micronutrients at constant supply of the
macronutrients.
SCHARRER and JUNG (1956) grew corn on a nutrient solution in which the microelements Mn, Cu, Zn, Fe, B, Mo and Co were present in varying quantities. Low
yieldswereobtained byadding Coinexcessand byomitting one of the other microelements.The effect ofthe growth rate on the (C—A) content can be studied in this
way.
k:
25
500
1000
mt./kg IC-A)
FIG. 27 a. The C and A contents of maize, supplied with different amounts of micro-nutrients.
b. The yields and (C—A) contents.
From data of SCHARRER and JUNG (1956).
The C and A contents are given in figure 27a. The growth differences resulted in
different degreesofexhaustion, whichinturn causeddifferent CandA contents.The
50
corn plants maintained, however, their (C—A) content close to 1000 me./kg. The
cluster of observations around 400 me./kg of A concerns plants with good growth.
The (C—A) content is somewhat lower here than with the other plants, probably
because nitrogen, asjudged bythe zero NO3content, was in rather short supply. The
yield and the (C—A) content are plotted in figure 27b. The (C—A) content is close
to 1000 me./kg whereas the yield varied markedly. Hence, the (C—A) content is not
afunction ofgrowth. Combined with the data of figure 24, a normal (C—A) content
appears to be one of the conditions necessary for maintenance of a good growth rate.
Thisconclusion wasconfirmed bya similarexperiment of SCHARRERand JUNG (1956)
with horse beans, although Fe-shortage resulted there in an excessively high (C—A)
content. It is known that iron induced chlorosis may go together with a high organic
anion content.
8.4
POTASSIUM-SODIUM REPLACEMENT
The normal (C—A) content of barley is maintained over a wider range when K is
replaced by Na (figure 22a and c),than when K is replaced by Ca (figure 20a and c).
However, with extreme K shortage in the presence of Na, weak barley plants developed which had lost their ability to maintain the normal (C—A) content.
The change of contents with K shortage and Na excess is shown more in detail by
results of VAN DEN BERGH (IBS, Wageningen). Two grass species, perennial rye-grass
mo./kg
ma./kg
2000 -
2000
N
1000
' - ' _ . . .
9
Y.^
' \
>—s.
1000
CO
0
•
[ • — - ^ t ^ -
0
4 0 « — Na
•40
0
tO -— No
K — * tO '
0
mi.
0
tO«—Na
K — » tO
0
mt.
FIG. 28 K-Na replacement diagrams of perennial rye-grass (a) and foxtail (b) grown together. The
(C—A)contentsandtheyieldsaregiveninfigurecand d.Data of VAN DENBERGH,IBS,Wageningen.
51
and foxtail (Alopecuruspratensis), were grown in mixed culture in containers and K
exhaustionwasachievedbycuttingafewtimesbefore applyingthetreatments.Mixed
culture ensures that the nutrient supply is the same for both species throughout the
growing period.
Theresultsaregiveninfigure28.The(C—A)content ofperennialrye-grassremains
constantat 1000me./kgoverawiderange.With40me.NaN03theK contentisonly
140me./kg so that the yield is completely governed by the K uptake. Under these
conditionsperennialrye-grassaccumulatesexcessiveamounts ofNa andanions.This
was also the case in the experiment offigure22, but there it was associated with a
(C—A)contentlowerthannormal,whereasitisabovenormalinfigure28forperennial
rye-grass.
Referring to the regulatory mechanism postulated in 6.3, it seems that the plants
are unableto transport cations other than K readily downwards.Thebreakdown of
regulation at high Na and low K doesnot occur in thefoxtail offigure28,probably
because this speciescannot take up Na at a rate comparable to that of K.
8.5
APPLICATION OF CHLORIDES
Theyield ofbarleyfertilized with30me.Ca(NOs)2wasunchanged bytheaddition of
30me.KCl.Thiswasassociatedwiththedifficulty ofrelievingthestressonthe (C—A)
content bygivingKtogetherwithCI.However,the saltlevelsinthe soilweresohigh
that osmotic damage might have interfered.
To study the problem in more detail oats were grown under similar conditions as
the barley plants ofthe experiment of section 7.The potswere fertilized with 20me.
KjtCa
KCl
m«./kg
1000
\
A ^ *
•
—--0
'Cl
0*.
20
m«.K
FIG. 29 Pot experiment with oats. The cation contents (a) and anion contents (b) at three levels of
a KforCa and a KCl application. The (C—A) contents and the yields for these treatments and for
application of K2SO4are given in the figures c and d.
52
20
mt.K
NO3. The K was applied by replacing the Ca of Ca nitrate with K, or by applying
KCl or K2SO4up to amounts of 20me.These arelevels at which, according to the
experience with barley, no serious osmotic damage occurs.
The (C—A) contents (figure 29c) and the yields (figure 29d) of the plants supplied
withKinsteadofCaandintheform ofsulphatearepracticallythesame.Thesulphate
treatments yielded somewhat less, but this difference between both forms of K application appeared unreproducible (compare figure 19).
Theresults oftheK for Caand KCltreatmentsdeserveadetailedcomparison. The
(C—Ä) content oftheplantsfertilized withCa(NC>3)2isonly650me./kg.Sincethe K
contentis400me./kg,theseplantssuffered from astressonthe(C—A)content rather
than from a specific K shortage.The stressisrelieved by the KforCa treatment but
not by the KCl treatment (figure 29c). Likewise, the yield of the KCl treatment is
lower over the whole range (figure 29d).
The stress of the (C—A) content in case of CIapplication was associated with an
increased A content in the barley experiment. However, in this experiment it is associatedwithalower Ccontent,andthesameA contentcomparedwiththeK for Ca
treatment. Afurther comparison oftheresults showsthat with20me.K as K nitrate
the nitrate content is high and the CI content low and that with 20 me. K as KCl
ClishighandNO3correspondinglylower(figure 29b).TheorganicNcontentis2500
and 2100me./kgfor the KNO3and KCltreatments,respectively. Thepresence ofCI
resulted in a lower transport of nitrates and organic anions to the top, so that the
(C—A) content was not maintained at its normal value of 950me./kg (section 6.3).
Asdiscussedin 7.3.2, K has two functions in the plant: a specific function and its
function as a positive charge accompanying the organic anions. KNO3, K2SO4and
K-clay are good sources to meet the requirements for both functions. When K is
m«.Nuptake
O Co(N03)2-H<2Sqt
X NH^Cl+KjSOj
o Ca(N0 3 ) 2 *KCl
+ NH«Cl + KCl
FIG. 30 The effect of N-application on the N-uptake (a) and the protein production (b) and the
relation betweenN uptake andyield(c)ofrapeseed,fertilized withnitrogen asCa(N03>2orNH4CI
with K2SO4or KCL From data of BÜCHNER(1952).
53
belowthespecificrequirement of200me./kgKClisalsoanadequate Ksource.When
Kismainlyrequired asapositivecharge,accompanying the anions, KClmay suffice
as long as K is absorbed in a sufficient excess to CI, which again depends on the
supply with NO3and otherions.
In the soil, CI is easily transported with the water. During this transport the accompanying cations are subject to exchange with other cations, mainly Ca. Hence,
CI, applied as KCl, reaches the roots mainly as CaCl2, so that a KCl application to
the soil maybemore harmful than KCl supplied in solution. If there isleachingthe
sameprocessleads to a removal of CIwith Ca,whereas K is retained.
8.6
AMMONIUM FERTILIZATION
Nitrateisreadilyabsorbedandtransformed tothereduction stageofammonia before
it is assimilated into organic compounds, and ammonium is also readily absorbed.
Any differences in response to either form of nitrogen are therefore related to their
different effects ontheionicbalance ofplant and solution (STREET and SHEAT, 1958;
NIGHTINGALE, 1937).
Some effects of ammonium fertilization are illustrated in figure 30, based on data
of BÜCHNER (1952),who supplied rape plants with different amounts of NH4C1and
Ca(N03)2innutrient solutions,addingKintheform ofKCl or K 2 S0 4 . The relation
between applied amount ofnitrogen and uptake of N isgiven in figure 30a.TheuptakeofNishighestwith(NH4CI+ K2SO4)andthelowestwith Ca(N03)2. Likewise
theproteinproduction(figure30b)isthehighestwith(NH4C1 + K 2 S0 4 ).Ammonium
is apparently the better source of N for protein production.
But it is seen infigure30cthat the relation between dry matter production and N
uptake isby far the most favorable for the treatments with nitrate. The plants with
mtrate produced about 8g of dry matter and those with (NH4C1+ KCl) only 5g
of dry matter at an uptake of 10me.N. Even though ammonia is a good nitrogen
source,theplants treated withthision did not growverywell,especiallywhen theK
was given as KCl.
Other data, mentionedin 8.3,suggestthatplants canmaintain their (C-A) content
inthetopsonlyifapartofthenitrogenistransportedupwardasNO3-.Consequently,
withammoniaasthesolenitrogensourcea stressonthe(C-A) contentmaydevelop.
Moreover, the ammonium ion maycompetewiththe Kion duringuptake. Sincethe
N from the ammonium ion is incorporated in the protein and its positive charge
releasedasH+,theammoniumionisofnouseasfarasthemaintenanceofthe (C-A)
content is concerned.
The competitive effect of NH 4 on the uptake of Rb is shown by an experiment
withexcised roots ofbarleygiveninfigure31. TROMP(1962)studied the interactions
m theabsorption ofammonium, potassium and sodium byroots ofwheat plants.He
showed that the K uptake isreduced to one-half orlessbythe concurrent uptake of
54
Rb
uptake
lO- 6 ^!«.
0.59 g
1<r«q.Rb/l
lO^eq-Rb/lt
10- 2 «q.NH«/l
minutes
of NH4CIon the Rb uptake by excisedbarleyrootsfrom RbCl
Fio. 31 The effect of the presence
g
100
SO
2"00
1000
1000
m«./kg(C-A)
• NH<3=fcN0j
2000
mt./kg (C-A)
1000
mt./kg Org.Anion!
O NO) without K
FIG 32 The organic anion contents and the (C-A) contents (a) and the (C-A) contents and
S d s (b) for tobacco fertilized with ammonium and nitrate in different proportions. Data of
r X y i e w f a n d t r g a n i c anion contents of Bryophyllumfertilized with ammonium and nitrate in
d i f f W r o p o r t i o n s and withnitratein theabsence of potassium.Data of PUCHER etal. (1947).
55
ammonium. These observations suggest that ammonium as a nitrogen source may
lead to plants with a stress on the (C—A) content and therefore to plants with a
lower yield.
Somedirectinformation onthissubject canbeobtained from data of VICKERYetal.
(1940) and PUCHER etal. (1947),who cultivated tobacco andBryophyllum calycinum
withvaryingamounts ofammonium andnitrateinthenutrient medium.The (C—A)
contentandtheorganicanioncontent oftheleavesoftobacco aregiveninfigure32a.
Theobservationsarearoundthe 1:1 lineoverthewholerangefrom 100%ammonia
to 100%nitrate so that this relation found for nitrate appears to be essentially the
same for ammonium. The relation between the yield and the (C—A) content of
tobaccoisgiveninfigure32b.Withhighammonium,theyieldis50gandthe (C—A)
content about 800me./kg. High yields are obtained only at (C—A)contents around
1800 me./kg, reached by giving nitrogen mainly in the form of nitrate. A similar
relation was found between the yield and organic anion content of Bryophyllum
(figure32c),whichwasobtainedbyvaryingtheform ofnitrogensupplyorbyomitting
potassium from the solution withnitrate.
9P
o
«o
o
o
O NOJ
O NH{N03
0
500
1000
m*./kg (C-A)
FIG.33 Potexperimentwithoats.Yieldsand(C—A) contentsofoatsfertilized withN asNÜ4,
NH4NO3andNOs.
The experiment with oatsdiscussedin 8.3included alsotreatments with nitrogen as
(NH4)zSO4andNH4NO3 attherate of20me.and Kattherates of0, 10and20me.
per pot as the chlorides or sulphates. Yields and (C—A) contents of all treatments
are summarized infigure33.Whatever the fertilizer treatment, good growth can be
expected onlyifthe(C—A)contentismaintained arounditsnormal value.Theyield
of4.5gata (C—A)content of650me./kgfor thetreatment 20me.N asNH4NO3 +
10me.K2S04 and the data offigures32b and 32cindicate that the (C—A) content
maybeless critical when ammonium and nitrate are applied together.
56
SCHARRER and JUNG (1955) reported some data on the composition of perennial
rye-grass, harvested far in thefloweringstage. The C and A contents are given in
figure 34. The normal (C—A) content at this advanced stage is apparently about
mt./kg A
FIG. 34 The relation between the Cand A content of perennial ryegrass far in the flowering stage,
fertilized with N as NO3, NH4NO3and NH4 fertilizer. From data of SCHARRER and JUNG (1955).
500me./kg. It was reported that the plants fertilized with NH4NO3in combination
with other fertilizers had a loweryieldthan the plants withnitrate onlyand that the
plants with ammonium had very low yields. The NH4NO3 plants maintained the
normal (C—A) content at a low yield, which shows again that a normal (C—A)
content is only one oftheconditions for a good yield. However, the plants fertilized
with NH4-salts had both a lowyield and a low (C—A) content.
8.7
BUCKWHEAT
The plant species discussed up to nowhave a normal (C—A) content of about 1000
me./kginthevegetativestage.Thedata of PIERCEand APPLEMAN(figure 4)showthat
there are plant species such as spinach, buckwheat and beets,with an organic anion
content of about 5000me./kg.
In anexperiment with buckwheat it was studied to what extent this high (C—A)
content isa condition for good growth.
The results of the K-Ca replacement series with the nitrate at 20 me. is given in
figure 35. The cation content (figure 35a) increases from the already high level of
2000 to 4400 me./kg with increasing K. The anion content (figure 35b) remains
constant around 340 me./kg and the (C—A) content increases from about 1700 to
4000me./kg(figure 35c). Theyieldincreasesfrom 2.2to 5.3grams(figure 35d),which
indicatesthat thishigh(C—A)content of4000me./kgandhenceaK content around
this valuearenecessary for good growth.
57
Theplantsfertilized with20me.Ca(N03)2plus20me.K 2 S0 4 yielded 4.5gand had
a (C—A) content of about 5000me./kg, whereas the ammonium nitrate treatments
yielded2gramswitha(C—A)contentofabout 1200me./kg.Likewise20me.Ca(N03)2
plus 20me.CaCl2 yielded 1.3 gwith a (C—A) content of only 2200 me./kg. In this
respect buckwheat responds about the same asthe oats(8.5).
me./kg
mi./kg
a
«000 ,i
(i
\yT
2000
s o
•
©__Ça
/ H i
No
= ^ 1
K—«-20
0
_ü°2_
2 0 - * - Ca
K—*-20
0
FIG.35 Thecationcontent(a),anioncontent(b),the(C—A)content(c)andtheyield(d)ofbuckwheatgrownonaK-Careplacementseries.
Theplants treated with20me.KClplus20me.Ca(N03)2 or 20me.KN0 3 had an A
content of 800 me./kg, and a C content of 5350 me./kg. The (C—A) content was
therefore about normal at 4500me./kg, but the yield was only 3.2 grams. The yield
was probably reduced by an osmotic stress in the soil, whereas the relative uptakes
oftheionsappeared tobesuchthatthenormal (C—A)content couldbemaintained.
This result shows again that a normal (C—A) content is one, but not the only one
condition for good growth.
58
9 IONIC BALANCE OF PLANT AND SOIL
9.1
SUMMARY
Well-nourishedplantshaveeitheranexternalalkaline oranexternalacidiceffect. An
external acidic effect isassociated with a net movement of metallic cations from the
soilcomplextothesoilsolution,whereasanexternalalkalineeffect isassociatedwith
a net movement of metallic cations from the soilsolution to the soilcomplex.
9.2
EXTERNAL ALKALINE AND ACIDIC EFFECTS
The cation and anion uptake by good growing grass is given in figure 17b.As long
as nitrate is not exhausted the anions are taken up in excess to the cations. During
this process of excess anion uptake, electroneutrality is maintained by a net uptake
ofH+ions.Thisexternalalkalineeffectwithnutrientsolutionsisreflectedinadecrease
ofthe H + concentration ofthe solution. In the presence of the soilcomplex this decreasein H+concentration isbuffered by the exchange of H+from the soilcomplex
withmetallic cations from the soil solution. The processis depicted in the left-hand
part ofthediagram offigure 36.Duringexcessanionuptake thereisa movement of
metallic cations to both the plant and the soil complex, and the soil complex is not
a source,butasinkfor metalliccations.WALKER(1960)pointstotheshift ofmetallic
external
alkaline effect
external
acidic effect
C+
c+
plant
decreasing [H + J
soil solution
C+ AH+ O H -
Increaslng [ H + ]
H+
C+
C+
soil complex
H+
FIG.36 Ionicbalanceofplantandsoil.
59
cations from the soil solution to the soil complex as a result of the external alkaline
effect. During further growth nitrate eventually comes to exhaustion and from there
oncations aretaken upinexcessofanions.Infigure17bthecurve doesnot intersect
the 1:1 line sothat the net external effect remains alkaline.
Irrespective of the nutritional status the organic N content of grass always exceeds
the (C—A) content so that grass always has an external alkaline effect. This also
holds for the barley of figure 23 and the oats of figure 29, both of which had an
organic N content of around 2500 me./kg and a (C—A) content of at the most
1250me./kg.
Thebuckwheatplantsoffigure35tookupabout4000me./kgcationsand3000me./kg
anionswhenfertilized withKNO3.Duringtheprocessofexcesscationuptakeelectroneutrality ismaintained by a net release of H+ions.This external acidic effect is,in
nutrient solutions, reflected in an increase of the H+ concentration of the solution.
In the presence of the soilcomplex this increase in the H+concentration is buffered
by the exchange of metallic cations from the soil complex with H+ from the soil
solution. This processis depicted in the right-hand part of the diagram offigure36.
During excess cation uptake there is a movement of metallic cations from the soil
complexto the soilsolution to the plant. In this case the soil complex isa sourceof
metallic cations. When fertilized with Ca(N03)2 the buckwheat plants offigure35
tookupabout 2000me./kgcationsandabout 3500me./kganionsand,therefore, had
an external alkaline effect. Such an inversion of the external effect as a result of a
change of the nutritional status can occur only when the normal (C—A) content is
of the same order ofmagnitude asthe organic N content.
60
10 A TEST ON THE M A C R O N U T R I T I O N A L
STATUS OF GRASS
10.1
SUMMARY
A block diagram for evaluating thenutritional status of grassplantsisgiven.Its application isillustrated with someexamples.
10.2
SPECIFIC REQUIREMENTS
Asdiscussedin section 1,N and Saresufficient iftheNO3-andSO4—contentsofthe
plant are higher than 100and 20 me./kg. Adequacy of P supply is indicated by a
total H2PO4-content higherthan 70me./kg.Asamacroelement CI - isnot essential.
In the case of NH4 supply an organic N content higher than 2500me./kg indicates
adequate N supply, irrespective ofthe NÛ3"content (VAN BURG, 1962).
ContentsofAhigherthan250me./kgarecommonanddonotaffect growthprovided
that the ionic balance is maintained. Contents of A higher than about 1000me./kg
indicate excessive chloride or nitrate.
Specific shortages for K, Ca and Mgoccurwhentheir contents arelowerthan200,
50 and 50 me./kg. Na is considered nonessential as a macroelement. The nutrient
supply is balanced if the (C—A) content is normal. For grasses, grown under the
various conditions of the experiments discussed, this is about 1000 me./kg. This
quantity is necessary because the accompanying organic anions are required in this
amount for good growth. The specific requirements for each of the organic anion
speciesarenotknown.Nevertheless,atestonthenutritionalstatuscanbemadewith
data onthe macroelements only.
10.3
T H E TEST
The purpose of nutritional tests is to evaluate whether thenutrition is adequate for
good growth and, if not, to decide what measures should be taken to improve the
nutrition for the next similarcrop orfor the samecrop during subsequentgrowth.
Sincetheinterrelationsbetweenelementsare rather complexthetest is summarized
inablock diagram. A diagram, madefor plants of perennial rye-grass and orchard
grass in the vegetative stage, is given infigure37at the endof the paper. Decisions
are given astilted squares (<^>).Thefirstsquare met contains (C—A) and has the
exits <900,>900 but <1100, and >1100.This decision symbols should be read as
61
follows: follow the lines at the exits <900, >900 but <1100 or ^1100 when the
(C—A) content islower than or equal to 900me./kg, between 900and 1100me./kg
or higher than or equalto 1100me./kg,respectively. Instructions aregiven asblocks
( • ) • Any instructions passed should be listed. If at any decision step the content
is close to a value at the exit, one should follow both directions so that two lists of
instructions are obtained. It will appear that, where both listsdiffer, acompromiseis
possible.In thisway decisions with more than two alternatives are avoided.
10.3.1 Examples
The use ofthe diagram isillustrated by someexamples givenin table 12.
Example1 The(C—A) content oftheplantswithout fertilizer isslightlylower than
900andAislowerthan 1000.CIishigherthan250sothattheinstruction toomuch CI
isgiven.NO3islowerthan200andthe organicN lowerthan 2500me./kg, sothat N
is obviously needed. The form of N to be applied depends on the K content. Here,
K is below 600, and the instructions applyN asnitrateand applyK withoutCIare
given. Subsequently, Na excess and the specific shortages of P, Mg, S and Ca are
tested. Thesetests do not lead to further instructions.
With the (C—A) content 850the exit 900< (C—A) < 1100may also be followed.
Thisonlyleadstotheinstruction apply N. Acombination ofbothpathwaysindicates
that N isdefinitely short, some Kisrequired and the excess CIisnot serious.
Because of Ca nitrate application (C—A) dropped far below 900.A is below 1000.
SinceNO3ishigherthan200andKlowerthan400,theinstruction applyKispassed.
The P content of 70 indicates that the plants are at the verge of P shortage. The
instruction:toomuchCI,isnowby-passedbecause ofthenitrate application. With K
nitrate (C—A)isslightlybelow900,NO3above 200and K above 800,sothat except
for P no further instructions are given. The same result is obtained when the exit
900< (C—A) <1100 isused.
Example2 The (C—A) contents of the plants with 40me. K nitrate and with 26
me. K nitrate + 14me.Na nitrate are slightly higher than 1100. Whether the exit
900 < (C—A) <1100 or the exit >1100 isused it isfound that the plants needed N
but not K andmayhaveneededsomeadditional P.The K content oftheplantswith
14me.Knitrate + 26me.Na nitrate isslightly lowerthan 500sothat, apart from N
and P,these plants needed some K.
The path to be followed for the plants with 40me. Na nitrate is outlined in detail.
(C—A) is extremely high. Since K is much lower than 250,this is probably due to
extreme K shortage. Hence the instruction applyK. Nitrate is 450 which indicates
that someadditional N maybeneeded.Theboundary between the exitsfor nitrateis
fixedat the high value of 400because the increase in yield following K application
results in an increased demand for N. Na is higher than 1000 and K is lower than
250so that the instruction toomuchNais given. Na istoo much because it islikely
that the uptake of K is considerably reduced by Na competition. According to the
62
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63
diagram P in this case is adequate but the other treatments show that after K application P may be short. Different exit boundaries for P, Mg, Sand Ca, depending
onthe K and N instructions arenot given because the boundaries havebeen chosen
well above the minimumlevel.
Inthecasethat (C—A)iswellabove 1300andKhigherthan250theplantsarelikely
to suffer from lime-induced or iron chlorosis. It may be that application of NH4
restores the balance (compare CAIN, 1952).
Example3concernsanexperimentwithsoiltreatedwithcalciumcarbonate(pH x 7)
or sulphuricacid (pH x 4.5)andwith(NH^SC^ or Ca(NÛ3)2.AtpH 7thereisno
difference between NH4and NO3fertilization because ofnitrification. Thereis some
N shortage but K is about sufficient. The same holds for the nitrate application at
pH 4.5. On the acid soil treated with NH4 the (C—A) content is much lower than
900andthe SO4content muchhigherthan 150,sothat theinstruction too much SO4
isgiven.NO3islowerthan200butorganicNhigherthan2500,sothattheinstruction
toomuchNH4is given. When (C—A) isnot lower than normal a similar path with
respect to nitrate and organic N doesnot givethe instruction: too much NH4.
Example 4 The test of the unfertilized plants yields only the instruction apply N.
AtestonCIisunnecessarybecausetheinstructionapplyKisnotgivenandthe(C—A)
content isnormal. The CIcontent of 280istherefore not too high.
With N application (C—A) islower than 900and A slightly higher than 1000and
theinstructionstoomuchCIandtoomuchNO3arepassed.FollowingtheexitA < 1000
theinstruction:toomuchNO3,isnotgivenbecauseasubsequent decreaseoftheNO3
content at further growthis expected.
With K application (asKCl + NaCl), (C—A)ismuchlower than 900and A much
higherthan 1000.WithCI1200theinstruction toomuch CIisgiven.Theexit boundariesfor theCItest areat alowvaluebecauseunder theseconditions anyreductionof
the high A content isuseful. NO3islow and K more than sufficient.
With the N and K application N shortage is relieved but the low (C—A) and the
high A contents are maintained.
Example5 Some plant compositions leading only to the instruction macronutrition
adequate are given in table 10.
10.3.2 Differences betweenplantsandcrops
In section 8it was shown that the yield differences resulting from different growth
ratesaremuchsmallerfor closedcropsthanfor singleplants,aslongasmoreextreme
shortagesareabsent.Therefore,inadequacy ofnutrition,foundbyapplyingthepresent
single plant test to closed crops does not necessarily imply that the crop yield is
significantly depressed. This smaller yield response of closed crops isfor the greater
part taken into account by changing thefigure900 at the exits of (C—A) into 750.
This boundary of 750 me./kg is based on experiments such as example 2, table 12,
with densily planted grassin pot experiments.
64
10.4
OTHER PLANT SPECIES
The normal (C—A) content of small grains in their vegetative stage is about 1200
me./kg. Apart from this they do not differ from grass. Therefore, the diagram for
grass plants is practically suitable for small grains if the values at the exits of the
(C—A) test areincreased by200.
The normal (C—A) content of buckwheat and beet is about 4500 me./kg. In this
case a simple adjustment ofthe diagram for grass cannot be satisfactory. Moreover,
beetandbuckwheat differ from grassandfrom eachotherwithrespect totherelative
uptake of thecations. Plantain didnot showpreference for any ofthe cations and a
test diagram for plantain would beentirely different from the diagram for grass.
Theseexamplessuffice toshowthattheconstruction oftestdiagramsfor otherplant
species requires similar basic information as given here for grass and smallgrains.
65
LITERATURE
BANGE, G. G. J.
BEAR, F . E.
BRIOGS, G. E., A. B. H O P E and
R. N . ROBERTSON
BROESHART, H. and
J. C H . V A N S C H O U W E N B U R G
BUCHNER, A.
B U R G , P. F . J. VAN
CAIN, J. C.
CARLES, J.
DIJKSHOORN, W.
DIJKSHOORN, W.
and
M. L . ' T H A R T
DIJKSHOORN, W. and
J. E. M. LAMPE
DIJKSHOORN, W., J. E. M. LAMPE
and P. F . J. VAN B U R G
EPSTEIN, E. and C. E. HAGEN
F R ΠD , M. and J C NOGGLE
H U R D , R. G.
66
1959 Interactions in the potassium and sodium absorption by
intact maize seedlings. Plant and Soil 11, 17-29.
1950 Cation and anion relationships in plants and their bearing
on crop quality. J. Amer. Soc. Agron. 42, 176-178.
1961 Electrolytes and plant cells. Oxford 1961.
1961 Early diagnosis of mineral deficiencies by means of plant
analysis. Netherl. J. Ägric. Sei. 9, 108-118.
1952 Über den Einfluss der Chlorionen auf den Kohlenhydratund Stikstoffhaushalt der Pflanze bei Ammoniak- b.z.w.
Nitraternährung. Z.Pflanzenern. DüngungundBodenk. 57,
1-29.
1962 Interne stikstofbalans produktie van droge stof en verouderingbij gras. Versl. Landbouw/c. Onderz. nr. 68.12., 131p.
1952 A comparison of ammonium and nitrate nitrogen for blue
berries. Proc. Amer. Soc. Hort. Sei. 59, 161-166.
1960 Le métabolisme des acides organiques dans l'ensemble de
la plante. Encyclopedia of Plant Physiology 12-2, 663-700.
Berlin.
.
1956 De opneembaarheid der kationen uit oplossingen bij
Engelsraaigrasenkropaar. Verslag
C.I.L.0.7955,187-195.
1957 A note on the cation-anion relationships in perennial ryegrass. Neth. J. Agric. Sei. 5, 81-85.
1958 Nitrogen and potassium in perennial rye-grass and,their
a relation to the mineral balance. Neth. J. Agric. Sei. 6,
131-138.
1958 Nitrate accumulation, nitrogen balance and cation-anion
b ratio during the regrowth of perennial rye-grass. Neth. J.
Agric. Sei. 6, 211-221.
1960 Het effect van de nitrificatie van een ammoniumbemesting
op de nitraat-accumulatie en de kation-anion balans in
Engels raaigras. Jaarboek I.B.S., 123-134.
.1962 Metabolie regulation of the alkaline effect of nitrate utilization in plants. Nature 194, 165-167.
1957 The effect'of alteration of temperature upon the cationic
cpmposition in perennial rye-grass. Neth. J. Agric. Sei. 5,
18-36.
1960 Nitraat in de stikstofbepaling volgens Kjeldahl. Jaarboek
I.B.S., 135-137.
1961 Phosphorus fractions in perennial rye-grass. Jaarboek
I.B.S., 101-106.
1960 A method of diagnosing thé sulphur nutrition status of
herbage. Plant and Soil 13, 227-241.
1952 A kinetic study of the absorption of alkali cations by
barley roots. Plant Physiology 27, 3 5 7 ^ 7 4 .
1958 Multiple site uptake of individual cations by roots as
affected by hydrogen ion. Plant Physiology 33, 139-144.
1956 The effect of p H on salt uptake by plant tissues. Thesis Un.
of London.
1938 Cation equilibria in plants in relation to the sou.. Soil
Science 46, 175-186.
1948 Cation equilibria in plants in relation to the soil II. Soil
Science 65, 393-416.
JACOBSON, L . arid L . O R D I N
1954 Organic acid metabolism and ion absorption in roots.
Plant Physiology 29, 70-75.
JACOBSON, L.
1955 Carbon dioxidefixation andionabsorbtioninbarley roots.
Plant Physiology 30, 264-269.
1951 Leaf analysis, London.
LUNDEOÂRDH, H .
1959 Investigations on the mechanism of absorption and accumulation of salts. Physiol. Plant. 12, 336-341.
1933 Untersuchungen über die Salzaufnahme der Pflanzen III.
LUNDEGÂRDH, H . U n d
Biochem. Z. 261, 235-251.
H . BURSTRÖM
1937 Thenitrogen nutrition ofgreen plants.Bot. Rev. 3, 85-174.'
NIGHTINGALE, G. T.
NOGGLE, J C, C. T. DE W I T
1963 Interrelations of Calcium and Rubidium by excised loots
of barley and plantain. S.S.S.A. Proc. (in press).
and A. L. FLEMING
1940 The absorption of bicarbonate ion by barley plants as
OVERSTREET, R . , S. RUBEN
indicated by studies with radioactive carbon. Proc. Nat.
and T. BROYER
Ac. of Sei. (U.S.) 26, 688-695.
1943 Role of ether soluble organic acids in the cation-anion
PIERCE, E. C. and
balance of plants. Plant Physiology 18, 224-238.
C. O. APPLEMAN
1947 Studiesinthemetabolism ofcrassulacean plants;the effect
PUCHER, G . W . ,
upon the composition of Bryophyllum calycinum of the
C. S. LEAVENWORTH,
form in which nitrogen is supplied. Plant Physiology 22,
W. D . GINTER and H . B. VICKERY
205-227.
1952 ZurPhysiologie desKaliums. Z. Pflanzenern. Dängn-"; und
RATHJE, W.
Bodenk'. 57, 151-163.
1952 Zur Physiologie des Chlors. Z. Pflanzenern. Düngung und
Bodenk. 57, 163-168.
1959 Cation selectivity and cation-anion balance as factors
SAID, I. M .
governing the mineral composition of pasture herbage.
Versi. Landbouwk. Onderz. 65. 16,64 p.
1955 DerEinfluss derErnährung auf dasVerhältnis von KatioSCHARRER, K. and J. J U N G
nen zu Anionen in der Pflanze. Z. Pflanzenern. Düngung
und Bodenk. 71, 76-93.
1956 Über denEinfluss von Mangan, Kupfer, Zink, Eisen, Bor,
Molybdaen undKobalt auf die Mineralstoflaufnahme bei
Mais und Ackerbohnen. Z. Pflanzenern. Düngung und
Bodenk. 75, 47-66.
1954 Theabsorption ofpotassium bytheplant.Potassium Symp.
SCHUFFELEN, A. C.
169-181. Bern.
1958 The absorption and availability of nitrate and ammonia.
STREET, H . E. and D . E. G. SHEAT
Encyclopedia of Plant Physiology 8, 150-161.
1956 Theselectiveabsorption ofalkali cations bystorage tissues
SUTCLIFFE, J. F .
and intact barley plants. Potassium Symp. 1-11.
1957 The selective uptake of alkali Nations by red beet root
tissue, J. Exp. Bot. 8, 36-49.
1962 Interactions in the absorption of ammonium, potassium,
TROMP, J.
and sodium ions by wheat roots. Acta Bot. Neerl. 11,
147-192.
U L R I C H , A.
1941 Metabolism of non-volatile organic acids inexcised barley
roots as ielated to cation-anion balance during salt ac. cumulation. Am. J. of Bot. 28, 526-537.
1952 Physiological basis for assessing the nutritional requirements of plants. An. Rev. Plant Phys. 3, 207-228.
I T A L L I E / T H . B . VAN
67
ViCKERY, H . B., G. W. PUCHER,
A. J. WAKEMAN and
C. S. LEAVENWORTH
VlETS, F . G.
VOLTERRA, V.
WALKER, F. W.
WALLACE, T.
WATSON, D. J.
WIT, C. T. DE
WYBENGA, J. M.
68
1940 Chemical investigations of the tobacco plant VIII. The
effect upon the composition of the tobacco plant of the
form in whichnitrogen is supplied. Conn.Agr. Expt. Sta.
Bull.442.
1944 Calcium and other polyvalent cations as accelerators of
ionaccumulation byexcisedbarleyroots.PlantPhysiology
19,466-480.
1928 Variations and fluctuations of the number of individuals
in animal species living together. In: R. N. CHAPMAN,
Animal Ecology. New York 1931,409-448. Original in J.
du Cons.int.p. l'Expl. delaMer III vol.1,1928.
1960 Uptake of ions by plants growing in soil. SoilScience89,
328-332.
1944 The diagnosis of mineral deficiencies in plants by visual
symptoms. London 1944.
1952 The physiological basis of variation in yield. Adv. Agron.
4, 101-145.
1958 Transpiration and crop yields. Versl. Landbouwk. Onderz.
64.6, 88p.
1960 On Competition. Versl. Landbouwk.Onderz.66.8, 88p.
1957 A contribution to the knowledge of the importance of
sodium for plant life. Thesis Agr. Univ., Wageningen.
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