Plant Physiol. (1986) 81, 792-797
0032-0889/86/81 /0792/06/$0 1.00/0
Effects of NaCl and CaCl2 on Ion Activities in Complex Nutrient
Solutions and Root Growth of Cotton'
Received for publication December 5, 1985 and in revised form March 18, 1986
GRANT R. CRAMER, ANDRfE LAUCHLI*, AND EMANUEL EPSTEIN
Department of Land, Air and Water Resources, University of California, Davis, California 95616
ABSTRACT
Sodium displaces Ca2 from membranes (GR Cramer, A Liiuchli, VS
Polito Plant Physiol 1985 79: 207-211) and this can be related to the
(Ca2`)/(Na')2 activity ratio in the external solution (GR Cramer, A
Lauchli 1986 J Exp Bot 37: 321-330). Supplemental Ca2" is known to
mitigate the adverse effects of salinity on plant growth. In this report we
investigated the effects of NaCl (0-250 millimolar) and Ca2" (0.4 and 10
millimolar) on the ion activities in solution and on root growth of cotton
(Gossypium hirsutum L.). Ion activities were analyzed using the computer
program, GEOCHEM. Most ion activities in a 0.1 modified Hoagland
solution were significantly reduced by both NaCl and supplemental Ca2".
Ion-pair formation and precipitation were significant for some ions,
especially phosphate. Root growth of 6-day-old seedlings was stimulated
by low NaCl concentrations (25 millimolar). At higher NaCl concentrations, root growth was inhibited; the concentration at which this occurred
depended on the Ca2" concentration and the growth index used. Supplemental Ca2" mitigated the inhibition of root growth caused by NaCl.
There was a curvilinear relationship between root growth and the (Ca2")/
(Na+)2 ratio in the nutrient solution. The mechanisms by which Na+ and
Ca2 may affect root growth are discussed.
Salt stress may reduce plant growth by water deficits, ion
toxicity, ion imbalance, or a combination of any of these factors.
Cotton is one of the most salt-tolerant crops species (19). Growth
of cotton is most salt-sensitive in the seedling stage (1, 3). In
previous studies, we have shown that Na+ displaces Ca2" from
membranes and alters K+ and Ca2" transport in cotton roots (8;
GR Cramer, J Lynch, A Lauchli, E Epstein, unpublished results).
Supplemental Ca2` partly restores perturbations of selective ion
transport (GR Cramer, J Lynch, A Lauchli, E Epstein, unpublished results), ionic balance (5, 16), and growth (5, 10, 16)
incurred by salt stress in cotton.
Salinity can also affect the ion activities in solution by changes
in ionic strength (which affects the activity coefficient), ion-pair
formation, and precipitation (7). Previously, we showed that
consideration of the ion activities in solution was important in
describing the Na+-Ca2+ interactions at the plasmalemma; specifically, that the Ca2" activity at the plasmalemma surface was
related to the (Ca2+)/(Na+)2 ratio (parentheses denote activities)
in the external solution (7). In that study, we considered the ionic
interactions only in simple salt solutions. In this report, we
consider the ionic interactions in complete nutrient solutions
and describe their relationship to root growth.
'Supported by National Science Foundation grant DMB84-04442.
MATERIALS AND METHODS
Analysis of Ion Activities in Nutrient Solutions. Ion activities
in the nutrient solutions were calculated using the computer
program, GEOCHEM (25). The rationale for the use of this
program has been described previously (7). Briefly, the program
calculates ion activities by a method of successive approximations, taking into consideration ion-pair formation and precipitation.
Plant Growth Conditions. Cotton seeds (Gossypium hirsutum
L. cv Acala SJ-2) were planted in germination paper 'sandwiches'
(16). The sandwiches were inserted into slots of plastic racks
which were placed in aerated treatment solutions in 3.7 L plastic
containers for continual wetting of the germination paper. The
tops of the containers were covered with BM and T multipurpose
plastic wrap to minimize evaporation from the germination
paper and salt accumulation. The control solution consisted of
a 0.1 modified Hoagland solution (16) containing 0.4 mM Ca",
with a pH of 6.5. Treatments of NaCl (0-250 mm final concentration), NaCl and supplemental Ca2" (9.6 mM CaC12 to make a
10 mm final Ca2+ concentration), or KCI (50 mM final concentration) were added to the control solution. The temperature of
the nutrient solution was maintained at 27°C using a Lauda K2/RD constant-temperature circulator. When the cotyledons
emerged, the plants were irradiated with incandescent lighting
(400 ,umol m-2 s-'; 15:9 h day:night cycle). Plants were harvested 6 d after the start of seed imbibition. Root growth was
measured as length, fresh weight, and dry weight at harvest time.
RESULTS
Ion Activities in Relation to NaCI and Ca2 Concentration.
Additions of NaCI or CaCl2 significantly affected the activities of
most ions in solution. Here, we report only those ions (Mg2",
Ca2+, Na+, P04 species, and SO42-) whose concentrations were
reduced by ion-pair formation and precipitation by 10% or more
of their original concentration. Sodium activity in a complete
nutrient solution rose almost in direct proportion to increasing
concentrations of NaCl; supplemental Ca2" had no significant
effect (Fig. la). Magnesium (Fig. lb) and S42- (Fig. lc) activities
declined with increasing NaCl concentrations. Supplemental
Ca2" reduced activity of these ions further, particularly at low
NaCl concentrations. One should note that the original Mg2'
and S042- concentrations in solution were 100 ,uM. Calcium
activity was also markedly reduced by increasing NaCl concentrations (Fig. 2). Activity in the low Ca2" treatment (Fig. 2a) did
not decrease in a smooth manner as did that of the previously
discussed divalent ions. This is the result of changes in ion-pair
formation and precipitation with phosphate (data not shown).
Figure 3 demonstrates the complex ion interactions that can
occur in a complete nutrient solution when the composition and
ionic strength are altered. Phosphate is particularly susceptible
to precipitation and ion-pair formation. As percentages of all
Downloaded from on June 17, 2017 -792
Published by www.plantphysiol.org
Copyright © 1986 American Society of Plant Biologists. All rights reserved.
EFFECTS OF NaCl AND CaC12 ON ION ACTIVITIES
793
E
U
4
ct
0.
+
z
4
U
O-
5sr.
b
N
0
4.5
4.0
F
._
U
3.5 -
.S-
4
N
20
2.5
F
0
100
I50
NoCI (mM)
50
s
-
40
0
4
20
0
50
100
150
NaCI (mM)
200
250
FIG. 1. Effect of added NaCl on ion activities in a 0.1 modified
Hoagland solution (pH 6.5). a, Na+; b, 100 AM Mg; c, 100 AM SO42. (/-A), 0.4 mM Ca; (LI---U), 10 mm Ca.
phosphate present, the phosphate species bound with hydrogen
(H3PO4, H2P04-, and HP042-) increased with NaCl concentrations (up to 50 mM) for the low Ca2+ treatment (Fig. 3a), while
phosphate bound or precipitated with Ca decreased (95% of the
phosphate is as a precipitate at 0 mm NaCI). As NaCl concentrations increased, Na+ formed ion-pairs with phosphate, reducing
phosphate activity even more. At 10 mm Ca>, phosphate activity
completely dominated by precipitation with Ca2 (Fig. 3b).
The activity of H2P04- was affected differently by increasing
NaCl concentrations at low and high external Ca>2 concentrations (Fig. 4). At the low Ca>2 concentration, H2PO4- activity
varied between the range of 61 and 95 AM, increasing at low, but
declining at high NaCl concentrations (Fig. 4a). At high Ca>2
concentration, H2PO4- activity was very low and varied between
the range of 0.3 and 0.9 uM, increasing steadily with increasing
NaCl concentrations. The original concentration of phosphate
was 200 uM.
250
0.1 modified
Effects of NaCI and Supplemental Ca2" on Root Growth.
Having examined the effects of NaCI on the activities of various
ions in a complete nutrient solution, we attempted to relate these
findings to the growth of cotton roots in solutions characterized
by their ion activities. Root growth was measured by several
indices: tap root length (lateral root development was minimal
at this age), fresh weight, and dry weight. At 0.4 mM Ca2", tap
root length was significantly reduced at 50 mM NaCl and above
(Fig. 5). At 10 mm Ca2 tap root length was increased at low
NaCl concentrations, reaching its maximum at 100 mM NaCl,
and was only reduced to values significantly below its control at
250 mm NaCI. At low Ca2" and high NaCl concentrations, the
roots turned brown, particularly at their tips, whereas with the
high Ca2+ treatment, the roots appeared healthy and white, even
at 250 mm NaCl. Similar trends were evident for the fresh weight
of roots (Fig. 6a). There was an increase at low and a reduction
at high NaCl concentrations. The dry weight of roots was not
significantly increased at low, but was significantly reduced at
high NaCl concentrations (Fig. 6b).
The NaCl concentration at which there was a decline in growth
varied with the index measured. Of the three indices measured,
tap root length was increased to the largest extent, and reduced
the least, for the high Ca2+ treatment. In contrast, tap root length
appeared to be the most NaCl-sensitive parameter at the low
Ca2" concentration. The fresh weight:dry weight ratio was reduced to below its control value at NaCl concentrations of 150
mm and beyond (Fig. 6c). The high and low Ca2+ treatments had
no significant effect on this ratio.
Root Growth in Relation to Ion Activities in Solution. Since
supplemental Ca2+ stimulated root growth, tap root length at
varied NaCl concentrations was plotted against the Ca2' activity
in the external solution for both Ca2' treatments (Fig. 7). Although root growth within each Ca2+ treatment appeared to be
,
0
was
200
FIG. 2. Effect of added NaCl on Ca2" activity in a
Hoagland solution (pH 6.5). a, 0.4 mm Ca; b, 10 mm Ca.
60
._
F
I
n L..
2I^
80.
0
3.0
Downloaded from on June 17, 2017 - Published by www.plantphysiol.org
Copyright © 1986 American Society of Plant Biologists. All rights reserved.
794
Plant Physiol. Vol. 81, 1986
CRAMER ET Al.
100
a
80S
60
40
201
*-., --
06
O-
ct
(I,
60
0.9
b -o
IL.
w
a-
--_
-.*
1oo
+
_
_
_
__
_
_
_
.
____
N
In
80
_-
60
F
40
F
0.7
-o~~~~.-.
-~
~
~
~
.
0.5
20 _
0.3
0
0
a1r
I
I
50
100
i
150
I
2250
200
NoCI (mM)
FIG. 3. Effect of added NaCI on phosphate species (% of total phosphate concentration). a, 0.4 mM Ca; b, 10 mM Ca. (A-A), P04 bound
with H; (@---4), P04 with bound and precipitated Ca; (O
50
-1
-O),
-
100
150
NoCI (mM)
200
250
FIG. 4. Effect of added NaCl on H2PO4- activity in a 0.1 modified
Hoagland solution (pH 6.5). The phosphate concentration was 200 uM.
a, 0.4 mM Ca; b,
10
mm Ca.
20
P04
bound with Na.
E
related to the reduction in Ca2" activity, the latter could not
account for the differences in root growth between Ca2" activity
of 2.34 mM (250 mM NaCl and 10 mM Ca2") and 0.2 mm Ca2"
(25 mM NaCl and 0.4 mM Ca2"). Previously, we showed that the
Ca2" activity at the plasmalemma surface was related to the
(Ca2+)/(NaNY ratio in the external solution (7). Since growth
might also be related to this ratio, root length was plotted against
it (Fig. 8). The (Ca2+)/(Na+)2 ratios were log transformed since
they differed by 10 orders of magnitude between the low and
high salt treatments. The log transformation did not affect the
conclusions derived from this plot. There was a distinct relationship between root growth and ion activity ratios (Fig. 8). Root
growth was maximal at a (Ca2+)/(Na+)2 ratio of approximately 1
(log 1 = 0), declining sharply at values below this ratio. At higher
ratio values root growth declined, but to a lesser extent. Similar
relationships were found for fresh and dry weights of roots (data
not shown).
Ion-Specific Effect on Root Growth. To test whether the inhibition by salt of root growth was cation-specific, tap root length
in the absence of salt was compared (Table I) with treatments of
50 mM NaCl or KCI in a modified Hoagland solution (0.4 mM
Ca2+). NaCl inhibited tap root length to a significantly greater
extent than did KCI.
DISCUSSION
Salt Effects on Ion Activities in Solution. The calculated results
of ion activities in a complete nutrient solution show that ion
'5
0
z
w
-J
I0
0
0
W.
4
5
I.-
0
0
50
ISO
100
NoCI (mM)
200
250
FIG. 5. Effect of added NaCI on cotton tap root length. The error
bars represent 95% confidence intervals for their respective curves. Each
value is the mean of 3 replications, with at least 17 subsamples (seedlings)
per replication (A-A), 0.4 mm Ca; (---O), 10 mM Ca.
interactions in a complex solution are much more significant
and complex than those found in a simple salt solution (7). These
interactions cannot be descibed by the simple assumption that
ion activities are determined principally by their activity coefficient. Some ions, such as K+, NO3-, and Cl- may fall into this
category, but others (particularly phosphate) do not, and require
one to consider the formation of ion pairs and precipitates.
Phosphate precipitation is not always readily visible in a nutrient solution, but may occur nonetheless, resulting in a sus-
Downloaded from on June 17, 2017 - Published by www.plantphysiol.org
Copyright © 1986 American Society of Plant Biologists. All rights reserved.
795
EFFECTS OF NaCl AND CaCl2 ON ION ACTIVITIES
40
0
h.
E
i4 4
-
0
0
w
Ua.
0
4
0
3
2
1
0
5
4
Activity (mM)
FIG. 7. Relationship between tap root length and Ca2+ activity in
solution (NaCl concentrations varied from 0 to 250 mM). (A-A), 0.4
m Ca; (0-0), 10 mm Ca.
Co
7
6
5
I
0~~~~~~~~~~--
0
0
20
4
0
E
-
O
o
3
E
15
I-
2
ohA
a
c
I
0
o F0
0
0
cr.
25
5
A
I.
¢ 20
0
I
-2
I
0
I
I
6
4
1
+2
log (Coa) /(No ) (mM)
8
I
2
II
2+
a:
>.
X
FIG. 8. Relationship between tap root length and the (Ca2`)/Na')2
ratio in solution. (A), 0.4 mm Ca; (0), 10 mM Ca. The parentheses denote
activities. NaCl concentrations varied from 0 to 250 mM.
15
U.
10
0
50
150
1OO
NOCI (mM)
200
250
FIG. 6. Effect of added NaCl on (a) fresh weight, (b) dry weight, and
(c) fresh weight:dry weight ratio of cotton roots. The error bars represent
95% confidence intervals for their respective curves. (A-A), 0.4 mM
Ca; (0---0), 10 mm Ca.
pended, invisible precipitate. Once precipitated, calcium phosphate redissolves very slowly. The pH of the solution can have a
substantial effect on these interactions. For example, using GEOCHEM, we have calculated that a 0.1 modified Hoagland solution at pH 6.5 has approximately 50% of the phosphate precipitated as calcium phosphate, but at pH 5.5 no precipitation
occurs. This effect may be significant for many nutrient solutions
since plants often alter the pH of the solution in which they
grow.
These findings indicate that addition of any salt not only
changes the concentration and activity of the ions added, but
can substantially alter the concentrations and activities of the
other ions present in solution. This is particularly important
Table I. Cation-specific Effects on Tap Root Length
The control was a 0.1 modified Hoagland solution (pH 6.5).
Ion Activity Ratioa
Tap Root Length
(Ca2+)
Treatment
(Total Cations)
cm
% of control
mM
100
11.9 ± 0.6b
Control
2.05 x 10-'
50 NaCl
7.0 ± 0.9
58
3.87 x 10-3
8.6 ± 0.6
73
3.75 x 10-3
50 KCI
b Mean ± 95% confidence interval.
' Parentheses denote activities.
mean
value with at least 13 subsamples
3
There were replications per
(seedlings) per replicate.
when one wants to study the effect of a specific ion in solution,
because of the usual implicit assumption that the activities of the
other ions do not change. For the studies of such ion effects, it
is therefore important to develop a system such as that of Bloom
and Chapin (4), in which the activities in the nutrient solution
can be closely monitored or have a computer program (such as
GEOCHEM) available for calculation of ion activities.
Effects of Na' and Ca2" on Root Growth. It is clear that NaCl
at high concentrations inhibited root growth and that this re-
Downloaded from on June 17, 2017 - Published by www.plantphysiol.org
Copyright © 1986 American Society of Plant Biologists. All rights reserved.
796
CRAMER ET AL
sponse was mitigated by supplemental Ca2", regardless of the
index of root growth examined. This effect was most pronounced
when tap root length was investigated.
Cotton root growth appears to be very sensitive to Ca2" concentrations (3, 10, 15, 16, 22, 23). Supplemental Ca" increased
Ca2 influx (GR Cramer, J Lynch, A Lauchli, and E Epstein,
unpublished results) and Ca2 tissue concentrations (16) for saltstressed cotton roots, supporting this hypothesis. However, the
Ca>2 activities in the nutrient solutions did not correlate well
with tap root length (Fig. 7). Root growth was better correlated
with the (Ca2+)/(Na+)2 ratio in the solution (Fig. 8).
Adams and co-workers (2, 14) suggested that it is the (Ca")/
(total cation) ratio (where parentheses denote activities) in the
nutrient solution that influence growth and Ca> sufficiency.
They found that cotton root length began to be inhibited at ratios
between 0.1 and 0.15, and markedly declined at ratios below this
value. Their hypothesis implies that ion-specific effects are not
important; they did not, however, investigate the effects of NaCl.
In our study, root length was not inhibited by 25 mM NaCl at
the low Ca> concentration, which has a (Ca2")/(total cation)
ratio that is less than 0.008. In addition, this ratio is slightly less
with KCI (3.75 x 1-0) than with NaCl (3.87 x 10-3) at 50 mM,
yet root growth was inhibited by NaCl to a greater extent than
by KCI (Table I). Thus, the hypothesis of Adams and co-workers
(2, 14) does not seem to take into account differences in growth
due to ion-specific effects, particularly in relation to salt stress.
In light of the present findings, their hypothesis requires modification to improve its general applicability. Our data were
plotted using their ion ratio; it did not fully account for the
differences observed between the two Ca>2 treatments (data not
shown). Our growth data were best described by the (Ca>2)/
(Na+)2 ratio, for which there is a theoretical basis (7). This implies
that it is the interaction between the Ca> and Na+ activities in
solution that is important for determining root growth of cotton
in saline solutions.
Calcium is important for normal plant function. It is involved
in cell wall extensibility and membrane stability and function,
and acts as a second messenger for many biochemical processes
within the cytosol (13). Cleland and Rayle (6) concluded that
Ca2> did not have any direct physical role in cell wall extensibility. Nakajima et al. (21), however, showed that cell wall extension
was inhibited by 50 mm CaCl2 and that this could be reversed
by replacement with 50 mM MgCl2. Furthermore, Soll and
Bottger (24) found that concentrations of NaCl or KCI between
100 and 1000 mm induced extension of coleoptile epidermal
strips. These authors concluded that Ca> was involved in cell
wall stiffening and that the exchange of Ca> from the cell wall
caused cell wall loosening.
Sodium probably displaces Ca> from the cell wall (24) and
should allow for rapid expansion, yet under saline conditions at
a low Ca> concentration (Fig. 5), cotton root growth was not
stimulated but inhibited. Extension or growth of the cell wall is
partly a result of synthetic processes (17). Plant cell wall polysaccharides and proteins are secreted to the apoplast by exocytosis ( 13). Griffing and Ray ( 12) suggested that cell wall secretion
may be regulated by intracellular Ca". Meindl (20) stated that
Ca> seemed to be a general mediator for recognition and fusion
processes of different types of vesicles at the plasmalemma.
According to Hanson (13) various ionic perturbations adversely
affect normal secretion, indicating that these ionic perturbations
may also alter membrane permeability and Ca> fluxes. He
further stressed that the regulatory system for macromolecule
secretion requires external Ca".
Calcium is also important for membrane stability and ionselective transport (9, 13). Sodium displaced Ca> from the
plasmalemma of cotton root hairs (8). Associated with this was
a loss of K+ from the root tissue and an alteration of K+/Na+
Plant Physiol. Vol. 81, 1986
selectivity (8, 16; GR Cramer, J Lynch, A Lauchli, E Epstein,
unpublished results). Potassium is important for normal protein
function and is an important solute for the maintenance of cell
turgor (18). A reduction in K+ tissue concentration could impair
these processes, essential for expansive cell growth. However, the
loss of K+ did not correlate well with the inhibition of root
growth by NaCl at 0.4 mM Ca". Root growth was inhibited by
50 mM NaCl (Fig. 5), but K+ efflux only increased at 150 mM
NaCl and beyond (8). Furthermore, 50 mM KCl inhibited root
growth (Table I), although this treatment did not displace membrane-associated Ca> (8). The leakage of K+ may indeed lead to
impaired growth of salt-stressed cotton roots, but only at high
NaCl concentrations.
Supplemental Ca> reduced the phosphate activity in the nutrient solution. Phosphate concentrations similar to those used
in this study were thought to be toxic in salt-stressed soybeans
(1 1). Cotton may respond similarly to these unrealistically high
phosphate concentrations under salt-stress. The nutrient solution
with the low Ca2"/salt treatments had 100 times the H2PO4
activity than did the high Ca2+/salt treatment (Fig. 4). However,
the changes in phosphate bound with H (Fig. 3) or H2P04activity (Fig. 4) did not correlate well with root growth (Fig. 5).
Root growth was stimulated at low concentrations of NaCl
(Figs. 5, 6, a and b). This may be due to increased turgor as a
result of a lower osmotic potential in the cell generated by the
uptake of NaCl. However, the high Ca>2 treatment stimulated
growth more than did the low Ca>2 concentration, yet Na+ influx
was significantly less in the high Ca>2 treatment (GR Cramer, J
Lynch, A Liuchli, E Epstein, unpublished results). Calcium may
affect growth by effects on cell wall extensibility (i.e. macromolecule secretion). At higher NaCl concentrations other factors
may come into play, such as the disruption of normal membrane
function, which could then lead to further physiological dysfunctions (8; GR Cramer, J Lynch, A Lauchli, E Epstein, unpublished
results). Thus, there appear to be complex interactions between
Na+, Ca2+, and growth.
In summary, NaCl at increasing concentration significantly
affected the activity of most ions in the nutrient solution. This
complicated the analysis of the growth data. Root growth was
stimulated by low NaCl concentrations, but was inhibited at
higher concentrations. Supplemental Ca>2 improved root growth
under saline conditions. KCI (at 50 mM) inhibited root growth
to a lesser extent than did NaCl, indicating that this inhibition
was partially ion-specific. Root growth was best related to the
(Ca2+)/(Na+)2 ratio in the external solution.
LITERATURE CITED
1. ABUI.-NAAS AA, MS OMRAN 1974 Salt tolerance of seventeen cotton cultivars
during germination and early seedling development. Z Ack Pflanzenbau
140: 229-236
2. BENNETT AC, F ADAMS 1970 Calcium deficiency and ammonia toxicity as
separate causal factors of (NH4)2HP04- injury to seedlings. Soil Sci Soc Am
Proc 34: 255-259
3. BERNSTEIN L, HE HAYWARD 1958 Physiology of salt tolerance. Annu Rev
Plant Physiol 9: 25-46
4. BLOOM AJ, FS CHAPIN III 1981 Differences in steady-state net ammonium
and nitrate influx by cold- and warm-adapted barley varieties. Plant Physiol
68: 1064-1067
5. CALAHAN JS JR 1977 Some physiological effects of high sodium, calcium, and
chloride concentrations on cotton. PhD thesis. Texas A&M University,
College Station
6. CLELAND RE, DL RAYLE 1977 Reevaluation of the effect of calcium ion on
auxin-induced elongation. Plant Physiol 60: 709-712
7. CRAMER GR, A LAUCHLI 1986 Ion activities in solution in relation to Na+Ca2" interactions at the plasmalemma. J Exp Bot 37: 321-330
8. CRAMER GR, A LAUCHLI, VS POLITO 1985 Displacement of Ca2" by Na+ from
the plasmalemma of root cells. A primary response to salt stress? Plant
Physiol 79: 207-21 1
9. EPSTEIN E 1972 Mineral Nutrition of Plants. Principles and Perspectives. Wiley
and Sons, New York
10. GERARD CJ 1971 Influence of osmotic potential, temperature, and calcium on
growth of plant roots. Agron J 63: 555-558
Downloaded from on June 17, 2017 - Published by www.plantphysiol.org
Copyright © 1986 American Society of Plant Biologists. All rights reserved.
EFFECTS OF NaCl AND CaC12 ON ION ACTIVITIES
11. GRATTAN SR, EV MAAS 1984 Interactive effects of salinity and substrate
phosphate on soybean. Agron J 76: 668-676
12. GRIFFING LR, PM RAY 1979 Dependence of cell wall secretion on calcium.
Plant Physiol 63: S-283
13. HANSON JB 1984 The function of calcium in plant nutrition. In PB Tinker, A
ULuchli, eds, Advances in Plant Nutrition, Vol 1. Praeger, New York, pp
149-208
14. HOWARD DD, F ADAMS 1965 Calcium requirement for penetration of subsoils
by primary cotton roots. Soil Sci Soc Am Proc 29: 558-562
15. JOHANSON L, HE JOHAM 1971 The influence of calcium absorption and
accumulation on the growth of excised cotton roots. Plant Soil 34: 331-339
16. KENT LM, A LXUCHLI 1985 Germination and seedling growth of cotton:
salinity-calcium interactions. Plant Cell Environ 8: 155-159
17. LABAVITCH JM 1981 Cell wall turnover in plant development. Annu Rev Plant
Physiol 32: 385-406
18. LEIGH RA, RG WYN JONES 1984 A hypothesis relating critical potassium
concentrations for growth to the distribution and functions of this ion in the
plant cell. New Phytol 97: 1-13
797
19. MAAS EV, GJ HOFFMAN 1977 Crop salt tolerance-current assessment. ASCE
J Irr Drain Div 103: 115-134
20. MEINDL U 1982 Patterned distribution of membrane associated calcium during
pore formation. Protoplasma 112: 138-141
21. NAKAJIMA N, H MORIKAWA S, IGARASHI, M SENDA 1981 Differential effect of
calcium and magnesium on mechanical properties of pea stem walls. Plant
Cell Physiol 22: 1305-1315
22. NELSON LE 1971 The effects of root temperature and Ca supply on the growth
and transpiration of cotton seedlings (Gossypium hirsutum, L). Plant Soil
34: 72 1-729
23. PRESLEY JT, OA LEONARD 1948 The effect of calcium and other ions on the
early development of the radicle of cotton seedlings. Plant Physiol 23: 516525
24. SOLL H, M BOTTGER 1982 The mechanism of proton-induced increase of cell
wall extensibility. Plant Sci Lett 24: 163-171
25. SPOSITO G, SV MATTIGOD 1980 GEOCHEM: a computer program for the
calculation of chemical equilibria in soil solutions and other natural water
systems. The Kearney Foundation of Soil Science, University of California,
Riverside
Downloaded from on June 17, 2017 - Published by www.plantphysiol.org
Copyright © 1986 American Society of Plant Biologists. All rights reserved.
868
INGEMARSSON ET AL.
Plant Physiol. Vol. 85, 1987
Plant Physiol. (1987) 85, 868
0032-0889/87/85/0868/01/$00.00/0
Correction
Vol. 81, 792-797, 1987
Grant R. Cramer, Andre Lauchli, and Emnanuel Epstein. Effects
of NaCI and CaCl on ion activities in complex nutrient solutions and root growth of cotton.
Page 793, Fig. 2b: For Ca2` Activity (PM) should read Ca2+
Activity (mM)
Page 795, Fig. 8: For log [(Ca2+)/(Na+)2J (mM-') should read
and for (Ca2+)/Na+)2 ratio should read (Ca2+)/(Na )2 ratio.