"—J—.
J.H.J.Spiertz
Department of Field Crops and Grassland Husbandry, Agricultural
university Wageningen
Grain production and assimilate utilization ofwheat
in relation to cultivar characteristics,
climatic factors and nitrogen supply
Centre for Agricultural
Publishing and Documentation
s
Wageningen - 1978
1
'' ',,fL
-z*é>i8Ql
'
-p—-^
ISBN9022006824
TheauthorgraduatedasDoctorindeLandbouwwetenschappenon10november 1978atthe
AgriculturalUniversityinWageningenonathesiswiththesametitleandcontents.
© CentreforAgriculturalPublishingandDocumentation,Wageningen,1978.
Nopartofthisbookmaybereproducedorpublished inanyform,byprint,photoprint,
microfilmoranyothermeanswithoutwrittenpermissionfromthepublishers.
Abstract
Spiertz,J.H.J. (1978)Grainproduction and assimilateutilization ofwheat
inrelation tocultivar characteristics,climatic factors and nitrogen
supply.Agric.Res.Rep. (Versl. landbouwk.Onderz.)881,ISBN 90 2200682 4,
(vi)+ 35p.,5figs, 1table, 149refs,Eng.andDutch summaries, summaries
ofNeth.J. agric.Sei. 19(1971): 211-222;Neth.J. agric.Sei. 21(1973):
282-296;NethJ. agric.Sei.22(1974): 207-220;Neth.J. agric.Sei. 25(1977):
182-197;Neth.J. agric.Sei.26 (1978): 210-231,233-249.
Also:Doctoral thesis,Wageningen (with complete articles).
Theeffects ongrainproduction of cultivar characteristics,nitrogen
supply and someclimatic factorswere studied infield trials and under
controlled environmental conditions.A rise intemperature considerably
increased therateof graingrowthbut shortened itsduration,whilst the
positive effect of light intensity on thegrainyieldwas greater athigh
temperatures.
Additionalnitrogen raised post-floral photosynthesis.Thenitrogen
assimilationby thegrainswas increased bywarmth,resulting inahigher
nitrogen concentration of thegrains and inearlier senescenceof theleaves.
Differences between a semi-dwarf cultivar and a standardweremainly expressed
inthedrymatterdistributionbefore and after anthesis and so inahigher
harvest-index.
Freedescriptors: Tritiowi
aestivum L.,wheat, leaf-areaduration, crop
photosynthesis,graingrowth,water-soluble carbohydrates,nitrogenuptake,
grainprotein,grainyield,harvest-index, temperature, light intensity,
semi-dwarf cultivar.
Contents
1 Introduction
1.1 General
1.2 Purposeofstudy
1.3 Literature
1.3.1 Growthofvegetativeorgans
1.3.2 Growthanddevelopmentoftheear
1.3.3 Source—sinkrelationsandthedistributionofassimilatesinthewheat
plant
1.4 References
1
1
2
3
3
4
5
7
2 Experimental studies
10
Summariesofthearticles
10
Relationbetweengreenareadurationandyieldinsomevarietiesofspring
wheat
10
Effectsofsuccessiveapplicationsofmanebandbenomylongrowthand
yieldoffivewheatvarietiesofdifferentheights
10
Graingrowthanddistributionofdrymatterinthewheatplantas
influencedbytemperature,lightenergyandearsize
11
Theinfluenceoftemperatureandlightintensityongraingrowthin
relationtothecarbohydrateandnitrogeneconomyofthewheatplant
11
Effectsofnitrogenoncropdevelopmentandgraingrowthofwinterwheat
inrelationtoassimilationandutilizationofassimilatesandnutrients 12
Cultivarandnitrogeneffectsongrainyield,cropphotosynthesisand
distributionofassimilatesinwinterwheat
12
3 General discussion
3.1
Sizeandactivityofthegreenorgansinrelationtograinproduction
3.2 Responseofgrainnumberandgraingrowthtoclimaticfactorsandnitrogen
supply
3.3 Assimilationandutilizationofcarbohydratesandnitrogencompounds
3.4 Agronomicpossibilitiesandlimitationsforincreasinggrainyield
3.5 References
14
14
16
16
21
24
27
Summary
30
Samenvatting
33
1 Introduction
1.1
GENERAL
Wheatisamongthemostimportantcropsforworld foodandfeedsupply (Table 1).
Muchwheatisgrownunderseasonalconditionscomparablewiththoseinwhichitevolved.
InMediterraneanclimates,vegetativedevelopmentandearinitiationoccuroncool,short
winterdays.Eardifferentiationtakesplaceunderconditionsofincreasingdaylengthand
temperature,whilegrainfillingoccursunderconditionsofhighsolarradiationand
warmth.Inmaritimeclimatesatmoderatelyhighlatitudes,asinWesternEurope,ear
differentiationtakesplaceunderlongandstillincreasingdaylengths,butoftenwith
relativelylowtemperaturesandpoorlightconditions.Duringgrainfilling,mostlyafter
midsummer,averagedaytemperaturesaremoderate.However,duetoannualandseasonal
variationsthetemperaturerangeisquitelarge.Undermorecontinentalclimates,the
winterwheatcropisexposedtoextremelowtemperaturesduringthewinterperiodandto
Table1.Acreage,yieldandproductionofarablecrops.Source:FAO-Yearbook,1975,
Crop
Acreage
(x1000ha)
Yield
(kg/ha)
Production
(x1000ton)
228169
25864
140880
1557
3025
2441
4987
2816
3842
1695
3056
355172
78245
343871
1893
322536
46406
155083
58187
46871
i
wheat
Rice
Maize
Barley
Millet
Pulses
Soybeans
Sorghum
Oats
Potatoes
Rye
Sugarcane
Cassava
Sugarbeet
World
Europe
World
Europe
World
Europe
World
Europe
World
Europe
World
Europe
World
Europe
World
Europe
World
Europe
World
Europe
World
Europe
World
Europe
World
Europe
World
Europe
380
114534
12079
9J504
19038
71354
657
24
1340
32
69560
4326
46463
661
641
45995
2774
68356
323
44599
134
31644
6446
21783
6400
15021
5389
12681
5
11551
1971
1369
1203
3563
1549
2617
13374
18247
1601
2406
50268
64585
9108
442
53632
477
49007
16870
291321
116784
24044
12966
637427
342
105209
-
-
-
8892
3716
28097
35301
249851
131175
heatanddroughtduringgrainfillinginmidsummer.Thusthewheatplanthasbeenadapted
byselectiontoawiderangeofclimaticconditions,especiallytovariationsin
temperatureanddaylength.
AsEvans&Wardlaw(1976)statedtherehavebeenfashionsintheemphasisonwhich
physiologicalprocesslimitscerealyieldandalsoonthestageofthecroplifecycle
regardedasmostcritical.Earlystudiesbyagronomiststogaininsightintothefactors
andprocessesthatdeterminegrainyieldswerebasedonyieldcomponentanalysis (Engledow
&Wadham,1923).Latergrowthanalysesintermsofdryweightincreaseperunitleafarea
becameanimportantresearchtool.Growthanalysisofcerealswereinitiatedandpromoted
byWatsonandco-workersatRothamstedExperimentalStation,England.Theyintroducedthe
conceptofleafareaindex (LAI),whichisdefinedastheratiooffoliageareatoground
area.Thisisconsideredasanimportantgrowthparameterfordeterminingyieldinrelation
toenvironmentalfactors (Watson,19S2).Themainresultsofthisapproachweresummarized
byThorne (1965).
Insubsequentyearsmuchmoreemphasishasbeengiventothefinalstageofthecereal
lifecycle;variousresearchworkers (Birecka&Dakic-Wlodkowska,1964;Stoy,1965;
Thorne,1966)havedemonstratedthatgraingrowthlargelydependsonpost-floralassimilation.Thengrainyieldwasassumedtobelimitedprimarilybyphotosynthesisandthe
supplyofassimilates.Thus,particularattentionwasgiventocropphotosynthesisthroughoutthegrain-fillingperiodasamajordeterminantofgrainyield (Puckridge,1971;
Baldy,1972;Lupton,1969;Apeletal.,1973;Austinetal.,1977;deVos,1977).More
recently,however,muchevidencehasbeenfoundtoshowthatthecapacityofthegrainto
storeassimilatesmaylimityieldjustasmuchasthecapacityofthecroptoprovidethe
grainswithassimilatesdoes (Bremner,1972;Rawsonetal.,1976;Fischeretal., 1977).
Othercropphysiologistshavegivenmoreattentiontoprocessessuchasassimilate
transport (Jenner&Rathjen,1975;Wardlaw,1968)andhormonalregulationofgraingrowth
(Radley,1976;Goldbach&Michael,1976;King,1976).
Anearly,morecomprehensivewhole-plantphysiologicalapproachofgrainproduction
inwheatwaschosenbyMiller (1939)andbyStoy (1965).Thiswhole-plantapproachwas
alsofollowedinmystudyoftheeffectsofclimaticfactorsandnitrogensupplyongrain
productionincontrastingwheatcultivars.
1.2 PURPOSEOFSTUDY
Thesequenceofexperimentscanbeclassifiedinthreegroups.Theaimofthefirst
groupofexperimentswastostudy:
-therelationbetweengreenareadurationandgrainyield,consideringthevariousgreen
organsofthewheatplantanddifferencesbetweencultivars;
-theinfluenceofaprolongedgreenareadurationongraingrowthandyield,bymeansof
latenitrogenapplicationsanddisease-controlwithfungicides.
Theseexperimentswerecarriedoutinthefield.
Aftersomepreliminaryshadingexperimentsinthefieldasecondgroupofexperiments,
carriedoutinacontrolledenvironment,weredirectedtostudytheeffectsoflight
intensityandtemperatureonrateanddurationofgraingrowthandconsequentlyonassimilationandutilizationofcarbohydrates andnitrogencompounds.Asink-sourceapproachwas
includedintheanalysisofplantbehaviour.
A thirdgroupofexperimentswascarriedoutinthe fieldunderthefavourablesoil
conditionsoftheFlevopolder.Theaimoftheseexperimentswastoanalyse:
-thesignificanceofannualvariationsinclimatic factorsforthepatternofgrain
production;
-theeffectofvariousnitrogentreatmentsoncropdevelopment,graingrowthandon
productionandutilizationofassimilates andnutrients;
-theeffectofcultivardifferencesondrymatterdistribution (carbohydrateandnitrogen
economy)inrelationtothepatternofgrainproductionandgrainyield.
Thefieldexperimentswerecarriedoutattheexperimental farmsoftheAgricultural
UniversityintheFlevopolderandinWageningen.Theexperimentsundercontrolled environmentalconditionsweredoneinthephytotronoftheDepartmentofFieldCropsandGrasslandHusbandryoftheAgriculturalUniversityatWageningen.
1.3 LITERATURE
Thedevelopmentsinthevarious fieldsofcropphysiology concerninggrainproduction
ofcerealsarecoveredbythefollowingreviews:Baldy (1972,1973),Thome (1974),
Evansetal. (1975),Austin&Jones (1976),Evans&Wardlaw (1976)andBiscoe&Gallagher
(1977).
Sincethereareextensivereviewsonmoregeneralaspects,thefollowingreviewjust
givesabackground fortheexperimentalworkpresentedinChapter3.Themost recent
literaturehasbeenpartly includedinthischapterandpartlyintheGeneral discussion
(Chapter4 ) .
1.3.1
Growth of vegetative
ovgam
Thevegetativephaseofthewheatplantextends fromshootemergencetoear initiation,
butgrowthofsomevegetativeorgans (e.g.roots,topleavesandstem)continuesuntil
anthesisandafterwards.Intheearlyvegetativephase leafandrootgrowthpredominate.
Rootgrowthmayexceedshootgrowthatlowtemperatures (Welbank, 1971),butastemperature
risesthegrowthofshoots increasesmorethanthatofroots (Brouwer, 1966).Shoot growth
thusappearstohaveahigheroptimum temperature thanrootgrowth;thisdifferencemay
result fromincreasedcompetition forassimilatesbetweenrootandshootathighertemperatures (Friend, 1966).Lowlight intensities reducerootgrowthandtillering (Baldy,
1973).Similarly,limitednitrogen supplymayreduce shootgrowth,butincreaseroot
extensionandtheratioroot:shoot (Brouwer, 1966).Lowerrootnumberscausedbynitrogen
deficiencyarecompensatedbygreaterlateral lengthsintheseminalbutnotthenodal
rootsystems (Tennant, 1976).
Usuallygrowthoftherootsystemcontinuesuntilheading,afterwhichroot growth
mayceaseandrootsmayevendegenerateduring thegrain-fillingperiod (Welbank, 1971).
Withanadequatewaterandnutrient supply,however,root growthandnutrient uptake
continuewellintothegrain-fillingperiod (Campbelletal., 1977).
Therateofleafformationaswellasthesizeofthematurelaminadependontemperature,lightintensity,daylengthandnutritionalstatusunderwhichtheplantisgrown
(Watson,1971;Friend&Helson,1976).Maximumleafareapershootisattainedwhenthe
flagleafhasfullyemerged (Watsonetal.,1963;Puckridge,1971).Leafarrangementisan
importantaspectofcanopystructure.Leavesformedpriortoearinitiationoriginate
closetothecrown,butelongationofsteminternodesseparatestheleavesinthevertical
plane,leadingtoamoreeffectivelightdistributionwithinthecanopy.
Throughouttheearlylifeofthewheatplant,theleafbladesarethemainphotosyntheticorgansandcropgrowthratedependsbothontherateofexpansionofleafarea
andtherateofphotosynthesisperunitleafarea.Theincreaseoftheleafareaindex
(LAI)iscloselyparalleledbytheincreaseincanopyphotosynthesis (Puckridge,1971).
Towardstheendofthelifecycle,photosynthesisbythestems,leafsheathsandears
tendstobecomeincreasinglyimportantastheleavessenesce (Austinetal., 1976).
Thestemgrowsconcurrentlywiththeleaves,rootsandear;rapideargrowthcoincides
withthatofthetopinternodes (Wardlaw,1974).Consequently,growthofthestemunder
limitingsubstrateconditionsmaycompetewiththatoftheear (Rawson&Hofstra,1969;
Patrick,1972).
1.3.2
Growth and development of the ear
Thedouble-ridgestageisusuallyconsideredasakeystageinthedevelopmentofthe
wheatplant,bymarkingtheendofvegetativedevelopmentandthebeginningofeardevelopment.Kirby (1974)suggestedthateardevelopmentcanbedescribedquantitativelyinterms
of (a)therateofspikeletinitiation,(b)thedurationofspikeletinitiationand
(c)thetotalnumberofprimordia.Bothleafandspikeletinitiationproceedatmoreor
lessconstantrates,butspikeletsinitiateconsiderablyfasterthanleaves.Therateof
eardevelopmentisaffectedbylightintensity,daylengthandtemperature (Friendetal.,
1963;Puckridge,1968;Rawson,1970;Lucas,1972).Thenumberoffertilespikeletsformed
increaseswithhigherlightintensities (Friend,1965);athighplantingdensitiesandin
denselytilleredstands,therefore,thenumberoffertilespikeletsmaybereducedby
mutualshading.Nitrogenmayaffectspikeletnumber,butonlywhenappliedbeforethe
stageofearinitiation;latenitrogendressingsmayincreasethenumberoffloretsper
spikelet (Langer&Lieuw,1973).Aftertheterminalspikelethasbeenformed,environmental
conditionsnolongerinfluencespikeletnumber,buttheymayaffectthenumberofflorets
differentiatedwithineachspikelet (Kirby,1974).
Differentiationofthespikeletprimordiastartsinthespikeletsinthelower-mid
partoftheear.Amaximumofninefloretsperspikeletmaybeformed,thoughsomeofthe
last-formedprimordiadonotproducefertileflorets (Kirby,1974).Hightemperaturesat
anthesismaycausesterilityanditappearsthatpollendevelopmentisparticularlysensitivetowaterstressandhightemperatures (Fischer,1973).Seedsetispromotedbyhigh
lightintensityduringfertilization (Wardlaw,1970)andisverysusceptibletowater
stress(Asana&Saini,1962).However,manyotherfactorssuchasthepositionontheear,
mayalsoaffectthenumberofgrainsset (Rawson&Evans,1970;Bremner,1972).
Aftercellwallformation,theendospermincreasesrapidlyincellnumberandsize
(Wardlaw,1970).Sofieldetai.(1977)foundarapidincreaseintheamountofwaterin
thegrainsduringtheperiodofactivecelldivisionandexpansionoftheendosperm,after
whichtherewaslittlenetchangeintheamountofwateruntilcompletionofdryweight
accumulation.Starchstoragebeginsonetotwoweeksafteranthesis,dependingontemperature.Inthegrain-fillingperiod,inwhichmostofthedrymatterofthegrainisaccumulated,grainvolumecontinuestoincreasebutatareducedrate.Fromthebeginningof
starchsynthesisonwardsthereisaperiodofalmostlinearincreaseindryweight,followed
byanasymptoticincreasetofinalgrainweight.Inthislastphase,theamountofwater
ofthegrainsdecreasesandgraingrowthstopsatabout401waterinthegrain (Jennings
&Morton,1963;Sofieldetal., 1977).Wedonotknowyetwhetherthedecreaseingrain
watercontentatmaturitycausesorisaconsequenceofthecessationofgraingrowth.
Radley (1976)suggestedthattheinitiationofwaterlossfromthegrainatmaturation
mightresultfromanincreaseinthepermeabilityofthepericarp.However,Sofieldetal.
(1977)concludedthatgraingrowthwasterminatedbyblockageofthetransportsystemby
lipids.Otherauthorssuggestedthattheaccumulationofabscisicacidinthegrainaffects
itsmaturation (Goldbach&Michael,1976;King,1976;Radley, 1976).
Temperaturehasapronouncedeffectontherateanddurationofgrain-filling
(Campbell&Read,1968).IntheexperimentsofAsana&Williams (1965)themaineffectwas
duetodaytemperature,butPetersetal. (1971)foundthatariseinnighttemperature
shortenedtheperiodofgrainfillingdrastically.Phytotronexperimentshaveshown,
however,thatitisdailytemperaturethathasapredominanteffectondurationofgrain
filling (Sofieldetal.,1974;Spiertz,1974;Warringtonetal., 1977).
Grainsindifferentpositionswithinaneargrowatdifferentratesandhavedifferent
maturegrainweights.Grainsinsecondfloretsbeginlaterbutmaygrowfasterandattain
a largerweightthanthoseinbasalflorets (Rawson&Evans,1970;Bremner,1972);grain
weightdecreasesfromthesecondflorettotheapicalfloret.Grainsintheupperspikelets
growmoreslowlythanthoseinthecentralspikelets;whenthesupplyofassimilatefrom
theleavesisreducedbydefoliationorshading,graingrowthismostseverelyreducedin
theupperspikelets (Bremner,1972).
Finalgrainsizedependstosomeextentonthenumberofgrainsperear.Bingham (1967)
foundthattheweightofgrainsinspecificpositionincreasesasgrainnumberperear
decreases.Thisobservationsuggeststhatgraingrowthmayhavebeenlimitedalsobythe
supplyofassimilates.However,grainyieldperearfellconsiderablyasthegrainnumber
wasreduced,indicatingarestrictedcompensationcapacityoftheremaininggrains.
1.3.3
Source— sink relations
and the distribution
of assimilates
in the wheat plant
Theterms 'source'and'sink'areoftenusedratherlooselyandwithvariousmeanings.
WarrenWilson (1972)suggestedthatsourcesandsinksshouldbedefinedintermsoflosses
andgainsofaparticularsubstanceinaparticularplantpart.Otherauthorsprefera
definitioninmetabolicterms,suchas:
-sourcesproduceassimilatesbyassimilationofcarbonandnitrogencompoundsorbymobilizationo*storedraaterials,while
-sinksutilizeassimilatesingrowthofstructuralandstoragematerialandinrespiration.
Thustheregionsofproductionandconsumptionofassimilatesintheplantarereferredto
as 'source'and 'sink',respectively (Wareing&Patrick,1975).
Usuallyincerealsthegrainsareconsideredassinkandthephotosyntheticactive
partsof.theplantassource.Thisconceptisanoversimplificationbecausethereare
alternativesinksinthewheatplant (stem,roots,tillers).Howevertheirpriorityand
capacityforutilizationofassimilatesislowerthanfortheear.Rawsonetal. (1976)
foundthattheresponseofleafphotosynthesistothelevelofassimilaterequirementby
theearwasinfluencedbythetreatmentofthevegetativetillers.Thus,thenetphotosynthesisrateoftheflagleafwasdecreasedbyareductioningrainnumberorincreased
byinhibitionofphotosynthesisintheear,onlywhenthevegetativetillerswerekept
defoliated;whenthesetillerswereallowedtogrownormally,therewasnoinfluenceof
eartreatmentonleafphotosynthesis.Thisobservationmightexplainthecontrastbetween
thefindingsofKingetal. (1967)andothers,whoobservedastrongdependenceoftherate
ofphotosynthesisintheflagleafofwheatonthelevelofrequirementforassimilateby
thedevelopinggrains,andthestudiesbyApeletal. (1973)andAustin&Edrich (1975)in
whichphotosynthesiswasindependentofthelevelofassimilaterequirement.
Aclosecorrelationbetweenfinalgrainyieldandvariousparametersofleafarea
afteranthesis (Welbanketal.,1966;Simpson,1968),togetherwiththefactthatmostof
thedrymatterincerealgrainsisphotosynthesizedafteranthesis (Thome,1965)have
frequentlyledtotheconclusionthatgrainyieldislimitedbythesupplyofphotosynthate
duringgrainfilling.Thisconclusionmaynotbemadeifinitialearsizeorpotential
grainsizeiscorrelatedwithleafareaatanthesisandwithleaflongevity.Treatments
involvingpartialdefoliation (Boonstra,1929)orpartialgrainremovalandinhibitionof
grainset (Bingham,1967)usuallyleadtodisproportionatelysmalleffectsonfinalyield
owingtophotosyntheticoryieldcomponentcompensation,respectively.
Reviewingtheliterature,Gifford (1974)concludedthatsourceandsinklimitations
usuallyco-existandareonlypartiallimitations.However,Stoy (1977)emphasizedthat
thephotosyntheticperformanceofthesourcesaswellassubsequentpartitioningofthe
assimilatesobviouslyarecontrolledmainlybythemetabolicactivityofthesinks.Stoy's
conclusionmightreferespeciallytothefirstweeksofgraingrowthwhenapoolofreadily
mobilisablereserves,mainlyinthestem,maycompensateforshort-termdeficienciesin
photosyntheticcapacity.Duringthesecondhalfofthegrain-fillingperiod,theinteractionbetweenenvironmentandgenotypemightdeterminetheratesofleafsenescenceand
grainmaturationandsotherelativelimitationbysourceorsinkcapacity.Constraintson
waterandnutrientsupplyaffectphotosyntheticcapacityoftheleavesmorethanthe
storagecapacityofthegrains,whichisreflectedbyafastdepletionandrelocationof
carbohydratereservesfromthestem(Asana&Saini,1962;Gallagheretal., 1976),andof
nitrogencompounds,mainlyfromtheleaves (Campbell&Read,1968).
Thedistributionofdrymatterbetweenthevariouspartsofthewheatplanthasbeen
consideredtobeconstantwithinaspecificdevelopmentphase (vanderSandeBakhuyzen,
1937).Theinitialinterdependencebetweenrootsandleavesisdisturbedfromearinitiation
onwards.Successivelystem,earanddevelopinggrainsbecomemajorsinksforcarbohydrates
andnitrogencompounds.RecentlySinclair&deWit (1975)madeacomparativeanalysisof
photosynthateandnitrogenrequirementsintheproductionofgrainsbyvariouscrops.They
concludedthattherequirementfornitrogenbythegrain,especiallywithhighprotein
grains,wassogreatthatmostlynitrogenmustbetranslocatedfromthevegetativeplant
tissuetothekernelstosustaingraingrowth.Arapidlossofnitrogenfromthevegetative
organsoftheplantcouldcauseadeclineinphysiologicalactivityandtherebylimitthe
lengthofthegrainJfillingperiod.Periodicanalysisofthechangesinnitrogencontent
ofthevariouspartsofthewheatculmshowedalossofnitrogenfromtheleavesandstem
concomitantwithanincreaseingrainnitrogen (vanderSandeBakhuyzen,1937;Williams,
1955).
Theincreaseintheamountofgrainnitrogen,however,frequentlyexceedstheloss
bytheleavesandstemduringgraindevelopment.Thebalanceofgrainnitrogenmustthereforecomefromnitrogenreservesintherootsorfromcurrentrootuptake.Depletionof
theleafnitrogenpoolsleadstoaprogressiveleafsenescencefromthebasetothetopof
thewheatculm.Thusabalancednitrogeneconomyofthewheatculmisaprerequisitefor
thephotosyntheticactivefunctioningoftheleavesduringthegrain-fillingperiod.
1.4 REFERENCES
Apel,P.,C O .Lehmann&A.Friedrich, 1973.BeziehungenzwischenFahnenblattfläche,PhotosyntheserateundEinzelährenertragbeiSommerweizen. Kulturpflanze 21:89-95.
Asana,R.D.&A.D.Saini,1962.Studiesinphysiologicalanalysisofyield.V.Grain
development inwheatinrelationtotemperature,soilmoistureandchangeswithage
inthesugarcontentofthestemandinphotosynthetic surface. Indian J. Fl.
Physiol.
5:128-171.
Asana,R.D.&R.F.Williams,1965.Theeffectoftemperaturestressongraindevelopment
inwheat. Aust. J. agrio. Res. 16:1-13.
Austin,R.B.&J.A.Edrich,1975.Effectsofearremovalonphotosynthesis,carbohydrate
accumulationandonthedistributionofassimilated Cinwheat. Arm. Bot. 39:141-J52.
Austin,R.B.,J.A.Edrich,M.A.Ford&R.D.Blackwell,1977.Thefateofthedrymatter,
carbohydratesand Clostfromtheleavesandstemsofwheatduringgrain-filling.
Ann. Bot. 41:1309-1321.
Austin,R.B.,M.A.Ford,J.A.Edrich&B.E.Hooper,1976.Someeffectsofleafpostureon
photosynthesisandyield inwheat. Ann. appl. Biol. 83:425-446.
Austin,R.B.&H.G.Jones,1976.Thephysiologyofwheat.Annualreport 1975,Plant
BreedingInstitute,Cambridge,20-73.
Baldy,Ch.,1972/1973.Surl'énergieactiveenphotosynthèse,sonutilisationpardes
graminéesaucoursdeleurdéveloppement. Annls agron. (23)6:685-699and (2411:1-3J.
Baldy,Ch.,1973.Progrèsrécentsconcernant l'étudedusystèmeracinair«dublé(Triticum
sp.). Armls agron. (24)2:241-276.
Bingham,J.,1967.Investigationsonthephysiologyofyield inwinterwheatbycomparisons
ofvarietiesandbyartificialvariationingrainnumberperear. J.agrio.
Soi., Comb.
68:411-422.
Birecka,H.&L.Dakic-Wlodkowska,1964.Photosynthesis,translocationandaccumulationof
assimilatesincerealsduringgraindevelopment.IV.Contributionofproductsof
currentphotosynthesisafterheadingtotheaccumulationoforganiccompoundsinthe
grainofspringwheat. Acta Soo. Bot. Pol, 33:407-426.
Biscoe,P.V.&J.N.Gallagher, 1977.Weather,drymatterproductionandyield.In:
J.J.Landsberg&C.V.Cutting (Eds),Environmentaleffectsoncropphysiology.
AcademicPress,London,NewYork,SanFrancisco,75-100.
'Boonstra,A.E.H.R.,1929.InvloedvandeverschillendeassimilerendedelenopdekorrelproduktiebijWilhelminatarwe. Meded. LandbHogesoh. Wageningen 33:3-21.
Bremner,P.M., 1972.Theaccumulationofdrymatterandnitrogenbygrainsindifferent
positionsofthewheatearasinfluencedbyshadinganddefoliation. Aust. J. biol.
Soi. 25:657-681.
Brouwer,R., 1966.Rootgrowthofgrassesandcereals.In:F.L.Milthorpe&J.D.Ivins
(Eds),TheGrowthofCerealsandGrasses.Butterworth,London,153-166.
Campbell,C A . ,D.R.Cameron,W.Nicholaichuk &H.R.Davidson,1977.Effectsoffertilizer
Nandsoilmoistureongrowth,N-contentandmoistureusebyspringwheat. Can. J.
Soil Soi. 57:289-310.
Campbell,C.A.&D.W.L.Read,1968.Influenceofairtemperature,lightintensityandsoil
moistureonthegrowth,yieldandsomegrowthanalysischaracteristicsofChinook
wheatgrowninthegrowthchamber. Can. J. PI. Soi. 48:299-311.
Engledow,F.L. &S.M.Wadham,1923.Investigationsonyield incereals. J. agrio.
Soi.,
Camb. 13:390-439.
Evans,L.T. &I.F.Wardlaw,1976.Aspectsofthecomparativephysiologyofgrainyieldin
cereals. Adv. Agron. 28:301-359.
Evans,L.T.,I.F.Wardlaw&R.A.Fischer,1975.Wheat.In:L.T.Evans (Ed),Cropphysiology,
somecasehistories.CambridgeUniversityPress.
Fischer,R.A., 1973.Theeffectofwaterstressatvariousstagesofdevelopmentonyield
processesinwheat.In:PlantResponsetoClimaticFactors.UNESCO,Paris,233-24J.
Fischer,R.A.,I.Aquilar&D.R.Laing,1977.Post-anthesis sinksizeinahigh-yielding
dwarfwheat:yieldresponsetograinnumber. Aust. J. agrio. Res. (28)2:165-1.76.
Friend,D.J.C, 1965.Earlengthandspikeletnumberofwheatgrownatdifferenttemperaturesandlightintensities. Can. J. Bot. 43:345-353.
Friend,D.J.C, 1966.Theeffectsoflightandtemperatureonthegrowthofcereals.In:
F.L.Milthorpe&J.D.Ivins (Eds),TheGrowthofCerealsandGrasses.Butterworth,
London,181-199.
Friend,D.J.C,J.E.Fischer&V.A.Helson,1963.TheeffectoflightintensityandtemperatureonfloralinitiationandinflorescencedevelopmentofMarqueswheat. Can. J.
Bot. 41:1663-1674.
Friend,D.J.C.&V.A.Helson,1976.Thermoperiodiceffectsonthegrowthandphotosynthesis
ofwheatandothercropplants. Bot. Gas. (137)1:75-84.
Gallagher,J.N.,P.V.Biscoe&B.Hunter,1976.Effectsofdroughtongraingrowth.
Nature 264:541-542.
Gifford,R.M., 1974.Photosynthetic limitationstocerealyield.In:R.L.Bieleski,
A.R.Ferguson&M.M.Cresswell (Eds),Mechanismsofregulationofplantgrowth.
Bull.No.12,RoyalSocietyofNewZealand,887-893.
Goldbach,H.&G.Michael,1976.Abscisicacidcontentofbarleygrainsduringripening
asaffectedbytemperatureandvariety. Crop Soi. 16:797-799.
Jennings,A.C.&R.K.Morton,1963.Changesincarbohydrate,proteinandnon-protein
nitrogenouscompoundsofdevelopingwheatgrains. Aust. J. biol. Soi. 16:318-331.
Jenner,C F . &A.J.Rathjen,1975.Factorsregulating theaccumulationofstarchin
ripeningwheatgrain. Aust. J. Pi. Physiol. 2:311-322.
King,R.W., 1976.Abscisicacidindevelopingwheatgrainsanditsrelationship tograin
growthandmaturation. Planta (Berlin) (132)1:43-51.
King,R.W.,I.F.Wardlaw&L.T.Evans,1967.Effectofassimilateutilizationonphotosyntheticrateinwheat. Planta (Berlin) 77:261-276.
Kirby,E.J.M., 1974.Eardevelopment inspringwheat. J. agrio. Soi., Camb. 82:437-447.
Langer,R.H.M.&F.K.Y.Lieuw,1973.Effectsofvaryingnitrogensupplyatdifferent
stagesofdevelopmentonspikeletandgrainproductionandongrainnitrogenin
wheat. Aust. J. agrio. Res. 24:647-656.
Lucas,D., 1972.Theeffectofdaylengthonprimordiaproductionofthewheatapex. Aust.
J. biol. Soi. 23:1-15.
Lupton,F.G.H., 1969.Estimationofyield inwheatfrommeasurementsofphotosynthesis
andtranslocationinthefield. Ann. appl. Biol. 64:363-374.
Miller,E . C , 1939.Aphysiologicalstudyofthewinterwheatplantatdifferentstages
ofitsdevelopment. Bull. Kansas St. agrio. Coll. 47,84pp.
Patrick,J.W., 1972.Distributionofassimilateduringstemelongationinwheat. Aust. J.
biol. Soi. 25:455-467.
Peters,D.B.,J.W.Pendleton,R.H.Hageman&C M . Brown,1971.Effectofnightairtemperatureongrainyieldofcorn,wheatand soybeans. Agron. J. 63:809.
Puckridge,D.W., 1968.Competitionforlightanditseffectonleafandspikeletdevelopmentofwheatplants. Aust. J. agrio. Res. 19:191-201.
Puckridge,D.W., 1971.Photosynthesisofwheatunderfieldconditions.III.Seasonal
trendsincarbondioxideuptakeofcropcommunities. Aust. J. agrio. Res. 22:J-9.
Radley,M., 1976.Thedevelopmentofwheatgraininrelationtoendogenousgrowth
substances. J. exp. Bot. 27:1009-1021.
Rawson,H.M., 1970.Spikeletnumber,itscontrolandrelationtoyieldperearinwheat.
Aust. J. biol. Soi. 23:1-15.
Rawson,H.M.&L.T.Evans,1970.Thepatternofgraingrowthwithintheearofwheat.
Auet. J. biol. Soi. 23: 753-764.
Rawson,H.M.,R.M.Gifford&P.M.Bremner, 1976.Carbondioxideexchangeinrelationto
sinkdemandinwheat. Planta (132)1:19-23.
.
Rawson,H.M.&G.Hofstra,1969.Translocationandremobilizationof Cassimilatedat
differentstagesbyeachleafofthewheatplant. Auet. J. biol. Soi. 22:321-331.
SandeBakhuyzen,H.L.vander,1937.Studiesonwheatgrownunderconstantconditions.
StanfordUniversityPress,California,400pp.
Simpson,6.M., 1968.Associationbetweengrainyieldperplantandphotosyntheticarea
abovetheflagleafnodeinwheat. Can. J. PI. Soi. 48:253-260.
Sinclair,T.R.&C T . deWit,1975.Photosynthateandnitrogenrequirementsforseed
productionbyvariouscrops. Science 189:565-567.
Sofield,I.,L.T.Evans&I.F.Wardlaw, 1974.Theeffectsoftemperatureandlighton
grainfillinginwheat.In:R.L.Bieleski,A.R.Ferguson&M.M.Cresswell (Eds),
Mechanismsofregulationofplantgrowth.Bull.No.12,RoyalSocietyofNewZealand,
909-915.
Sofield,I.,I.F.Wardlaw,L.T.Evans&S.Y.Zee,1977.Nitrogen,phosphorusandwater
contentsduringgraindevelopmentandmaturationinwheat. Aust. J. Fl. Physiol. 4:
799-810.
Spiertz,J.H.J.,1974.Graingrowthanddistributionofdrymatterinthewheatplantas
influencedbytemperature,lightenergyandearsize. Neth. J. agrio. Soi. 22:207-220.
Stoy,V..1965.Photosynthesis,respirationandcarbohydrateaccumulationinspringwheat
inrelationtoyield. Physiologia PI. Suppl.IV:1-125.
Stoy,V., 1977.Trockensubstanzproduktion undAssimilateinlagerungindasGetreidekorn.
Z. PflErnähr. Düng. Bodenk.140: 35-50.
Tennant,D.,1976.Rootgrowthofwheat.I.Earlypatternsofmultiplicationandextension
ofwheatrootsincludingeffectsoflevelsofnitrogen,phosphorusandpotassium.
Auet. J. agrio. Fes. 27:183-196.
Thome,G.N., 1965.Photosynthesisofearsandflagleavesofwheatandbarley. Ann. Bot.
27:155-174.
Thome,G.N., 1966.Physiologicalaspectsofgrainyield incereals.In:F.L.Milthorpe&
J.D.Ivins (Eds),TheGrowthofCerealsandGrasses.Butterworth,London,88-105.
Thome,G.N., 1974.Physiologyofgrainyieldofwheatandbarley.ReportRothamsted
ExperimentStationfor 1973.Part2,5-25.
Vos,N.M.de,1977.Wheat.In:Th.Alberda (Ed),Cropphotosynthesis:methodsandcompilationofdataobtainedwithamobilefieldequipment. Agrio. Res. Rep. 865,Pudoc,
Wageningen,22-30.
Wardlaw,I.F., 1968.Thecontrolandpatternofmovementofcarbohydrates inplants.
Bot. Rev. 34:79-105.
Wardlaw,I.F., 1970.Theearlystagesofgraindevelopment inwheat:responsetolightand
temperatureinasinglevariety. Aust. J. biol. Sei. 23:765-774.
Wardlaw,I.F., 1974.Thephysiologyanddevelopmentoftemperatecereals.In:A.Lazenby&
E.M.Matheson (Eds),CerealsinAustralia.AngusandRobertson,Sydney,58-98.
Wareing,P.F.&J.Patrick,1975.Source-sinkrelationsandthepartitionofassimilates
intheplant.In:J.P.Cooper (Ed),Photosynthesisandproductivityindifferent
environments.CambridgeUniversityPress,Chapter21,481-499.
WarrenWilson,J., 1972.Controlofcropprocesses.In:A.R.Rees,K.E.Cockshull,D.W.
Hand&R.G.Hurd (Eds),Cropprocessesincontrolledenvironments.London,Academic
Press,7-30.
Warrington,I.J.,R.L.Dunstone&L.M.Green, 1977.Temperatureeffectsatthreedevelopmentstagesontheyieldofthewheatear. Aust. J. agrio. Res. 28:11-27.
Watson,D.J., 1952.Thephysiologicalbasisofvariationinyield. Adv. Agron. 4:101-145.
Watson,D.J., 1971.Size,structureandactivityoftheproductivesystemsofcrops.In:
J.P.Cooper&P.F.Wareing (Eds),Potentialcropproduction.Heinemann,London,76-88.
Watson,D.J.,G.N.Thorne&S.A.W.French,1963.Analysisofgrowthandyieldofwinter
andspringwheats. Ann. Bot. 27:1-22.
Welbank,P.J., 1971.Rootgrowthofwheatvarieties.ReportRothamstedExperimentStation
for 1971.Part 1,104-106.
Welbank,P.J.,S.A.W.French&K.J.Witts,1966.Dependenceofyieldsofwheatvarieties
ontheirleaf-areadurations. Ann. Bot. 30:291-299.
Williams,R.F.,1955.Re-distributionofmineralelementsduringdevelopment. Ann. Rev.
Plant Phys. 6:25-42.
2 Experimental studies
SUMMARIESOFTHEARTICLES
Relation between green area duration and grain yield in some varieties
of spring wheat
J.H.J. SpiertZj B.A. ten Hagand L.J.P. Kupers, Netherlands Journal of
Agricultural
Science 19(1971): 211-222.
Intwoexperimentswithspringwheattherelationwasstudiedbetweengreenarea
duration(D)andgrainyieldduringtheperiodafterheading.Forthis,thegreenareas
ofleaf,internodeandearweredeterminedasaccuratelyaspossibleinsamples.
Therelationbetweengrainyieldandgreenareadurationoftheseparategreen
organsandofcombinationsofthesewasquantifiedbyregressionandcorrelation
calculations.Thesecalculationshaveshownthatoftheseparatepartsoftheculmthe
Dvaluesofflagleafandpedunclewerecloselycorrelatedwiththegrainyield.
ByusingthecombinedDvalueofflagleafandpeduncleasayielddetermining
factor,81and61%ofthevarianceinthegrainyieldcouldbestatisticallypredicted
in1967and1968,respectively.ByincludingalltheseparateDvaluesinamultiple
correlationcalculationthecoefficientsofdeterminationofthevarianceinthegrain
yieldcouldbeincreasedto83«.in1967andto74°sin1968.In1968,nexttotheDvalues
offlagleafandpeduncle,theDvalueoftheearwascloselycorrelatedtothegrain
yield.
Thephotosyntheticefficiencyofthegreenareawascomparedbythegrain-leafratio.
Effects
varieties
of successive
of different
J.H.J. Spiertz,
applications
of maneband benomyl on growth and yield of five wheat
heights
Netherlands Journal of Agricultural
Science 21(1973): 282-29S.
Theeffectofsomefungicidetreatmentsontheproductionpatternoffivewheat
varietieswithdifferentculmlengthswasinvestigatedinafieldexperiment.Thefungicide
treatmentsconsistedof:asequenceof2pre-floralsprayingswith2kgmanebperhaand
2post-floralsprayingswith1kgbenlateperha.ThevarietieswereJuliana(117cmculm
length),Manella(82cm),Lely(80cm),Mex.-cross(69cm)andGaines(79cm).Therewas
hardlyanymildewinthecropbutSeptoria
tritici
andSeptoria
nodorum wereverymuchin
evidenceinallthevarieties.Ofthegroupofripeningdiseases,blackmouldsand
Fusarium werefoundtoalesserdegree.
Thecombinedapplicationofmanebandbenomylgreatlydelayedthespreadof
Septoria
inthecrop,asaresultofwhichtheflagleafinparticularremainedgreenforalonger
periodandthegrainfillingperiodwaslengthened.Thegrowthrateofthegrainsduring
10
' •
"•
-1
thephasefromthemilk-ripestagetothedough-ripestagewasraisedfrom204kgha
-1
- 1 - 1
'
day to230kgha day .Theeffectoftheapplicationwasgreaterinthevarieties
mostsusceptibletoSeptoria (LelyandGaines)thanintheothervarieties.Theincreases
ingrainyieldofthevarietiesJuliana,Manella,Lely,Mex.-crossandGaineswere14%,
23%,32%,16%and42%,respectively.Bystatisticalanalysis85%ofthevarianceinthe
grainyieldwithinthevarietiescouldbeattributedtothegreenareaoftheflagleaf.
.Thus,themaineffectofSeptoria seemstobeareductionofthephotosyntheticarea,
causingadecreasedsupplyofassimilatestoreachthegrain,andinthiswaylowering
the1000-grainweight.
/ Thedegreeofdiseaseinfectionwasnotsignificantlycorrelatedwithculmlengthor
theamountofleafarea,sothetoleranceandresistancecharacteristicsoftheVarieties
werenotimmediatelyduetodifferencesincropstructure.Specificvarietydifferences
werestillpresent,evenafterreductionofthediseaseinfectionwiththefungicides.
Grain growth and distribution of dry matter in the wheat plant as influenced by temperature,
light energy and ear size
J.H.J. Spiertz, Netherlands Journal of Agricultural Science 22(1974): 207-220.
Anexperimentwascarriedoutundercontrolledgrowingconditionstostudytheplant
responseduringthepost-floralstagetotemperature,lightintensityandearsize.Within
therangeof15to25°Caraiseintemperature increasedthegrowthrateofthegrains
butthedurationofthepost-floraldevelopmentoftheplantwasverymuchshortened.The
finalresultwasthathighertemperaturescaused lowergrainyields.Anincreaseoflight
-2 -1
intensityfrom92to147calcm day hasshownamorepositiveeffectongrainweight
-2 -1
thananincreasefrom147to175calcm day .Theartificialreductionofearsizeby
removingspikeletsfromtheearincreasedthethousand-grainweightbutnotenoughto
compensateforthereductioninnumberofkernelsperear.
Theeffectsofthemainfactors-temperature,lightintensityandearsize-andof
thecombinedtreatmentsonthesupplyandstorageofcarbohydratearediscussedwithinthe
frameworkofasink-sourcemodel.
The influence of temperature and light intensity on grain growth in relation to the
carbohydrate and nitrogen economy of the wheat plant
J.H.J. Spiertz, Netherlands Journal of Agricultural Science 25(1977): 182-197.
Theresponseofgraingrowthtotemperatureandlightintensitywasstudiedunder
controlledconditionswithintherangesfrom10to25°Candfrom64to188Wm",respectively.Warmthhastenedthesenescenceofthewheatplantandenhancedtheinitialgrowth
rateofthegrains.Additionallightpromotedtherateofgraingrowthmoreathighthan
atlowtemperatures;underthelatterconditionstherewasaconsiderableaccumulationof
carbohydratesinthestem (upto40%)fromanthesisonwards.Therateofgraingrowth
-1
-1
rangedfrom0.70to1.64mgday kernel .Thedurationofgraingrowthwasprolongedby
decreasingthetemperaturefrom25to10°C;theincreaseingrowthdurationfromabout
30to80dayscorrespondedwitharelativelystabletemperaturesum.Temperatureandlight
i
11
alsoaffectedtheredistributionofassimilatesandthechemicalcompositionofthegrain.
Therateofproteinsynthesiswaspromotedmorebywarmththantherateofstarchsynthesis.Thisresultedinanincreasednitrogencontentofthegrain.Thefinalcontentof
totalnon-structuralcarbohydrates (starchandsugars)wasslightlydecreasedbywarmth.
Additionallightraisedthecarbohydratecontentofallpartsoftheplantandso
decreasedthenitrogencontentoftheseparts.However,lightintensityhadlesseffect
onnitrogendistributionandyieldthantemperaturehad.
Effects of nitrogen on crop development and grain growth of winter wheat in relation to
assimilation and utilization of assimilates and nutrients
J.H.J. Spiertz and J. Ellen, Netherlands Journal of Agricultural Science 26(1978): 210-231.
Graingrowthandyieldcomponentsofwinterwheat (cvLely)werestudiedinafield
experimentin1976withfourregimesofnitrogendressing (50,100,100+50and100+100
kgNha ) .Growingconditionswerecharacterizedbyahighlevelofsolarradiation,
warmth,amplenutrientsupplyandnodamagebydiseases.
2
Nitrogenraisedgrainnumberperm from16,700to20,600andgrainyieldfrom640
_2
to821gdryweightm .Graingrowthdurationwasshort,duetowarmth,buttherateof
-2 -1
grainfillingwasveryhigh:from24.0to29.2g m day duringtheeffectivegrain
fillingperiod.Ahighgrainyieldwasassociatedwithahighnitrogenpercentageofthe
grains,whichresultedinagrainproteinyieldrangingfrom63.8to107.1g m
withan
increasednitrogendressingfrom50to200kgha".
Thecarbohydratedemandofthegrainswasprovidedbycurrentphotosynthesisandrelocationofstemreserves.Thelatterwasreflectedinadeclineofthestemweightafter
themid-kernelfillingstage.Nitrogenandphosphorusdemandofthegrainsweresupplied
bywithdrawalfromthevegetativeorgans (leaves,stem,chaff)andtoalargeextentby
post-floraluptakeandassimilation.
Undertheprevailinggrowingconditionsthegrainsturnedouttobeverystrong
sinksforcarbohydrate,nitrogenandphosphorusasshownbytheharvest-indices.Additionalnitrogendressingsincreasedtheharvest-indicesofdrymatter,nitrogenandphosphorusfrom0.40to0.48,from0.75to0.81 andfrom0.91 to0.93,respectively.
Itwassuggestedthatamorerestrictedvegetativecropdevelopmentathighnitrogen
levelsandalongerdurationofrootactivity,photosynthesisandgraingrowthafter
anthesiswouldconsiderablyfavourgrainyield.
Cultivar and nitrogen effects on grain yield, crop photosynthesis and distribution of
assimilates in winter wheat
J.H.J. Spiertz and H. van de Haar, Netherlands Journal of Agricultural Science 26(1978):
223-249.
Acomparisonbetweenthecropperformanceofasemi-dwarf (MarisHobbit)anda
standardheightcultivar (Lely)atvariouslevelsofnitrogensupplywasmade.Grain
yieldsofHobbitwereconsiderablehigher,duetoahighernumberofgrainsandaheavier
12
grainweight.Owingtothehighergrainyieldandalowerstemweightth*harvest-index
ofHobbitwashighercomparedtoLely:0.47and0.40,respectively.Thecontentofwatersolublecarbohydrates inthestemsofbothcultivarsappearedtobeveryhighuntil 3weeks
afteranthesis,despitetheoccurrenceoflowlightintensities.Itwassuggestedthatdue
totheweatherof 1977lowtemperaturesrestricted earlygraingrowthandrespirationmore
thanphotosynthesiswasaffectedbylightintensity.Lelyusedmoreassimilates forstructuralstemmaterial thanMarisHobbitdid.
Quantityandtimeofnitrogenapplicationaffectedgrainnumberstrongly,butgrain
weighttoalessextent.Sowithineachcultivargrainnumberperm wasthemaindeterminantofgrainyield.Latenitrogendressingspromotedphotosyntheticproduction,grain
weightandproteincontentofthegrains.Thelowproteinpercentagesofthegrainswere
attributed tothelowtemperaturesduringthegrainfillingperiod.Thedistributionof
nitrogenwithinthewheatplantwasonlyslightly influencedbynitrogendressingsand
cultivardifferences.
Nitrogenharvest-index rangedfrom0.74 to0.79.Grainnitrogenwasderived fromthevegetativeorgans (63-94%)andfromuptakeafteranthesis (6-374).Theimportanceofcarbohydrateandnitrogeneconomy forgrainyieldarediscussed.
13
3 General discussion
3.1 SIZEANDACTIVITYOFTHEGREENORGANSINRELATIONTOGRAINPRODUCTION
FollowingtheworkofWatsonetal. (1963),Thorneetal.(1969)andWelbanketal.
(1966),westudiedtherelationbetweengreenareadurationandgrainyieldinspring
wheat,asaffectedbysowingdateandgenotypicdifferences.Therelationbetweengrain
yieldandgreenareadurationofthevariousgreenorganswerequantifiedbyregression
andcorrelationcalculations (Spiertzetal., 1971).Theresultsshowedthatgreenarea
duration,calculatedfortheperiodfromheadingtoripening,wasmorecloselycorrelated
tograinyieldthanthegreenareadurationfromfloweringtoripening.Itwassuggested
thatphotosynthesisduringthepre-anthesisperiodwouldaffectfinalgrainyieldby
influencingthenumberofgrainssetandtheamountofreservestemporarilystoredinthe
stem.
Sincethegreenareasofthevariouspartsoftheculmwerecloselyinter-related,
itwasnotpossibletocalculatetheexactcontributionofeachorgantograingrowth.
Judgingfromthedegreeofcorrelationbetweengreenareadurationandgrainyield,we
consideredthefollowingorganstobeimportantingrainfilling:especiallypeduncleand
flagleaf,followedbytheear,lastleafandlastintemodebutone.Thecoefficientof
2
determinationofthevarianceingrainyield (i?)amountedto0.83and0.74intwosuccessiveyears.Bylatesowingvegetativegrowthwasreducedmorethanearformation,sothat
thenumberofgrainsperunitgreenareawashigher.Consequentlythegrain-leaf-ratiowas
higher.However,inspiteofahigherphotosyntheticefficiencythelate-sowncropsyielded
less,becauseofaconsiderablylowergreenareaduration.
Similarlygoodcorrelationsbetweengrainyieldandgreenareadurationwerereported
byFischer&Kohn (1966),Simpson(1968)andHsu&Walton (1971).Inlaterexperimentsthe
correlationofgrainyieldwithgreenareadurationwasnotasgood.Especiallyunder
growingconditionsfavourableforleafgrowth-viz.highratesofnitrogensupply-apparentlygrainyieldwaslimitedbyfactorsotherthantheamountofgreenarea.Thorne&
Blacklock (1971)suggestedthatgrainyieldceasedtobewellcorrelatedwithgreenarea
_2
durationafteranthesiswhengrainyieldsexceededabout500g.m andleafareaindex
(two-sided)atanthesiswashigherthanaboutseven.However,suchcriteriadependon
growingconditions (lightintensity),cultivardifferences,occurrenceofdiseases,etc.
Generallythecorrelationofgrainyieldwithgreenareadurationishigh,whenvariationingrainyieldismainlycausedbytheweightoftheindividualgrainandnotby
grainnumber.Thisphenomenonwasshownbyanexperimentwithfivecultivarsofwinter
wheat (Spiertz,1973).Correlationsbetweengrainyieldandleafareawerepositivewithin
thecultivarsandnegativebetweenthem.Thecorrelationwasnegativebecausealowgrain
yieldinthecultivarJulianawasassociatedwithahighleafareadurationafteranthesis.
14
•"f"
ThereverseoccurredwiththecultivarGaines.Thevarianceingrainyieldwithinthecultivarscouldbeattributedfor85%totheVarianceingreenarea,oftheflagleafatthe
endofthekernel-fillingperiod.Thispercentageincreasedwhenvariousdegreesofleaf
infectionwereproducedinacultivarsusceptibleto Septovia sp.byadifferentfrequency
offungicideapplication.TheverysusceptiblecultivarLelyshowedacorrelationof 0.99
betweengrainyieldandpercentagegreenareaoftheflagleafon20July*Whilstthemore
resistantcultivarhadacorrelationcoefficientof0.33.Themaineffectofdiseaseslike
Septoria seemstobeareductionofthephotosyntheticarea,causingadecreasedsupplyof
assimilatestothegrainandasaconsequencealowergrainweight.
MorerecentlyLedent (1977a)studiedtherelationbetweengrainyieldandanumberof
plantcharactersinwheatcanopiesinthefieldandincontrolledenvironments.Simple
correlations,stepwiseregressionanalysisandfactoranalysisindicatedthattheplant
charactersmostcloselyrelatedtograinyieldweregrainnumber,stemdryweightand
weightofsheathsofflagleafandsecondleaf.Areasofleavesandinternodeswereless
stronglyrelatedtograinyieldinthecultivarsstudied.McNeal&Berg (1977)foundwith
near-isogenicpopulationsthatflagleafarea,byitself,wasnotagoodindexforplant
performance.Differencesinothercharacters (headingandplantheight),however,might
havebeenmoreimportantinthesenear-isogenicpopulations.
Removalofpartsofleaflaminaeorcuttingvascularbundlesintheupperleavesor
sheathsofwheatculmshadlittleeffectonmeanweightperkernel.Removalofentire
laminae,completeleafremoval,andcuttingvascularbundlesatthebaseoftheearsignificantlydecreasedmeankernelweight (Ledent,1977b). Inmostcases,thedecreasesvaried
by 10to20%.ThesefindingsconfirmtheresultsofWalpole&Morgan (1974);theycould
notdetectanysignificanteffectongrainweightinthe14daysafterdefoliation.Later
themoreseveredefoliationsreducedgrainweight,andreductionsinfinalgrainyield
rangedfrom16.6to45.5%.Generally,effectsofareductioninphotosynthetic capacity
ongrainyieldwilldependontheextenttowhichthe 'source'limitsgraingrowth.
CanopyphotosynthesisappearstoincreaseasymptoticallywithincreaseinLAI,
reachingamaximumlevelatLAIvaluesabove4 (Evansetal., 1975).Therelationbetween
netphotosynthesisandLAIwasunaffectedbyeithercultivarorbysowingdensity
(Puckridge&Ratkowsky,1971). Inourexperiments (Spiertz&vandeHaar,1978)additionalnitrogenappliedatthebootstagepromotednetphotosynthesismorethanitpromoted
LAI,especiallyinthelaterstagesofgraingrowth.Thisfindingshowstheimportanceof
maintainingthephotosyntheticactivityofthegreenorgansduringageingratherthan
increasingtheareaofthegreenorgansassuch.Towardtheendofgrainfilling,stemand
earphotosynthesiscanbecomethemajorsourceofcurrentphotosynthesis,buteveninthe
earlierstagesofgraingrowth,stemphotosynthesiscanbeasubstantialcomponent (Evans
& Rawson,1970).Thiscontributionfromthestemmightexplainthehighdrymatteryields
foundundergrowingconditionswhichdidnotfavourleafgrowth (Spiertz&Ellen,1978),
butpromotedtheformationofahighnumberofculms.
Graingrowthcanbealsoconsiderablyaffectedbythecarbondioxideconcentration
(Gifford,1977).C02-enrichment (0.20ml.1 )gavea324largertotalcropweightat
15
maturityanda43$increaseingrainyield,whilstareduction (-0.15ml.1 )gavea43%
reductionintotalcropweightand441reductioningrainyield.Mostofthegrainyield
responsewasbroughtaboutbyanincreasedfertilityoftheside-tillers;obviouslyincident
radiationwasnotlimiting.Osman (1971)showedthatnetphotosynthesiswasmoreclosely
relatedtolightinterceptionandcropgrowthratethantoleafareaindex.Photosynthesis-lightcurvesturnedouttobedifferentforthevariousleaflayers.Lower,andthus
shaded,leaveshadalowerlevelofmaximumphotosynthesisthantopleaves,duetoahigher
mesophylandcarboxylationresistance.
Hencethecharactersofthevegetativeorgansareonlypartlycorrelatedwithgrain
yield.Thedegreeofcorrelationdependsongrowingconditionsandonthedemandforassimilatesbythegrains.
3.2 RESPONSEOFGRAINNUMBERANDGRAINGROWTHTOCLIMATICFACTORSANDNITROGENSUPPLY
Grainyieldisafunctionofthenumberofgrainsperunitgroundareaandthemean
weightpergrainatharvest.The number of grains perunitgroundareaiscomposedofgrain
numberperearandnumberofearsperunitgroundarea.Biscoe&Gallagher (1977)concluded
thattheweatherinfluencesthephysiologicalanddevelopmentalprocesseswhichdetermine
thenumberofgrainsmorethantheprocessesdeterminingtheirsize.Thisconclusionis
confirmedbycomparingthevarianceingrainyieldandgrainnumberbetweenyearsinour
fieldexperiments (Fig.1).Therelationshipbetweengrainyield (7)andgrainnumber(ff)
forthecultivarLelyunderdisease-freeconditionsinthegrowingseasonsfrom1972-1977
couldbeexpressedbythefollowingformula:
y-=52.8+0.0357 N
(R=0.85)
Themainenvironmentalfactorsintheseexperimentswereweatherandnitrogensupply.If
otherfactorslikedisease,droughtandnitrogenstressinterfereduringthepost-floral
period,thentherateanddurationofgraingrowthwouldbefarmoreimportant(Spiertz,
1973).
Apparently,poorlightconditionsduringthepre-floralperiodcanseverelyreduce
yieldsinwheat (Willey&Holliday,1971;Fischer,1975).Evans (1978)foundthatear
2
number(rangingfrom402to1070perm)wascloselyrelatedtoirradianceduringthe
earlyreproductivestage(from35to15daysbeforeanthesis).Grainnumberperearwas
influencedmostlybyirradianceduringthelatereproductive"stage (from15daysbeforeto
5daysafteranthesis).However,Fischeretal. (1977)concludedthatgrainyieldinnormal
cropswaslimitedbybothsinkandpost-anthesissource.Theyestablishedawiderangein
grainnumbers(4000to34000perm )bythinning,shading,applicationofcarbondioxide
andcrowding.Grainyieldincreased,reachingamaximumatagrainnumberwellabovethose
ofcropsgrownwithoptimalagronomicmanagementbutwithoutmanipulation.Kernelweight
felllinearlywithincreaseingrainnumberoverthewholerangeofgrainnumbersstudied,
buttherateoffallvariedwiththeseason.Inourexperimentsadditionalnitrogenapplied
atthebootstageincreasedmostlythenumberofgrainsaswellasgrainweight (Ellen&
Spiertz,1975;Spiertz&Ellen,1978).Thustherearemanagementtreatmentswhichbreak
16
900
grain yield
g.m" 2
800
-1972
-1973
0 -1974
• -1975
A -1976
• -1977
A
O
700
600
500
•400
300
Y=0.0357X+52.8
(R=0.85)
200
O'-'V—L-
-J
6
8
1
1
10
L.
18
20
22
numberofkernelsxio3per m2
Fig. 1.Simple linearregressionofgraindrynatteryield (g.m )ongrainnumberperm
forsixsuccessiveyearswiththecultivarLely.
12
14
16
thecompensationmechanism.Thesamephenomenonwasseenintheexperimenttostudydifferencebetweencultivars (Spiertz&vandeHaar, 1978).Darwinkel (1978)variedplantden2
sityfrom5to800plantsperm andfoundalsoalinearrelationbetweengrainyieldand
2
grainnumberuptoabout 18000grainsperm .Abovethis levelanincreaseingrainnumber
wascompletely compensatedbyadecreaseinkernelweight.Theextenttowhichthegrains
arefilleddependsonthelocationwithintheearandonthesupplyofassimilates.
Bremner&Rawson (1978)suggested that thedifferentpotentials forgrowthofgrainswithin
a spikelethaveaminorinfluenceonmaturegrainweight,butthattherelativeeasewith
whichassimilatereachesthegrainhasamajorinfluence.Thelatterdepended largelyon
thedistanceofthegrainsfromthespikerachis.
Theeffectsofenvironmental factorsonthe rate and duration of grain grouth were studied
ingrowthchamberswithintherangesfrom10to25°Candfrom64to188W.m".Arisein
temperature increasedthegrowthrateofthegrainsconsiderably,butthedurationofthe
post-floralperiodwasverymuchshortened (Spiertz,1974,1977).Durationofgraingrowth
wasreducedfrom80to30daysbyariseintemperature from10to25°C.Similar temperatureeffectswerefoundinphytotronexperimentswithothercultivarsofspringwheat
(Sofieldetal.,1974,1977a;Ford&Thorne,1975;Warringtonetal., 1977;Chowdhury&
Wardlaw, 1978).Thusresponseingraingrowthofthewheatplanttotemperature seemsto
beverypredictable.
17
Growthrateofthegrainswascloselyassociatedwithmeandailytemperaturesafter
anthesis,aslongasassimilatesupplytothegrainscorrespondedtothedemand (Spiertz,
1977).Demandsofthegrains forassimilates increasedwithariseintemperature.Thereforetheeffectoflightintensityonrateofgraingrowthwasgreaterathighertemperatures.Inthephytotronexperiments,thehighest levelofphotosynthetic radiation
(16hours:188W.m )turnedouttobeinsufficientforanadequatesupplyofphotosynthate
athightemperatures.This shortageofassimilateswasalsoreflectedinafastdepletion
ofstemreserves.Sofinalgrainyielddependsonthebalancebetweensupplyofassimilates
andstoragecapacityoftheear.
Thequestionremainstowhatextenttemperatureaffectsrateanddurationofgrain
growthinthefieldcrop.UndergrowingconditionsintheNetherlands greatdifferences
areobservedintemperatureandlightintensity fromyeartoyear (Fig.2 ) .Inwinter
wheatexperimentswiththecultivarLely,theratesofgraingrowthbetweenyearsfrom
1972-1977werecompared.Peryearplotswithanoptimumnitrogendressingwere selected;
othergrowingfactorswereratherfavourableinthesefieldexperimentsintheFlevopolder.
Therateofgraingrowth (drymatter)perunitgroundarearangedbetweenyears fromabout
200upto350kg.ha .d (Fig. 3).Aftercorrection fordifferencesinsolar radiation
betweenyears,byexpressingtherateofgraingrowthperunitoflightintensity (ug.J ) ,
alsounderthesefieldconditionstemperaturewaspositivelyrelatedtograingrowthduring
theso-called linearphaseofgrainfilling (Fig.4A).Thedurationofgraingrowthturned
outtobeinverselyrelatedtotemperature (Fig.4B). Theseresponsesoffieldcropsto
temperature
(°C)
25
X-—x 1972
+—+ 1973
o—o 1974
23 • — A t975
- A — A 1976
21 h
1977
V
,*-*—A
/+
19
17
15
o
0
o'
13
15/6 20/6 25/6 30/6
5/7 10/7 15/7 20/7 25/7 30/7
dates
Fig.2.Meandaily temperatures during thekernel-fillingperiodinsixsuccessiveyears.
1!
temperatureagreeverywellwiththosefoundbyMarcellos&Single (1972)jMeredith&
Jenkins (1976)andPinthus &Sar-Shalom (1978).Underbrightconditionsassimilate supply
isfavouredmorethanthedemandsofthegrowing grains.Therefore individualgrainweights
infieldcrop^sarenotaffectedbytemperatureasmuchasthoseinthephytotronexperiments.
Evans (1978)foundthatgrainyieldofwheatgrowninaconstantdaylengthandtemperatureregimewasmorelimitedbyirradiancebetweenearinitiationandanthesis,when
storagecapacityisdetermined,thanbyirradiance duringgraingrowth.Sofieldetal.
(1977a)foundthatwithcultivarsinwhichgrainnumberwaslessaffectedbylightintensity,growthratepergrainwashighlyresponsivetoirradiance,especially inthemore
distalflorets.Theyconcludedthatgrowthratepergraindependedmainlyonfloretpositionwithintheear,ondifferencesingrainsizebetweencultivarsandontemperature.A
higherrateofgraingrowthincultivarswith largergrainsatmaturitywasalsofoundin
ourfieldexperimentwiththecultivarsLelyandMarisHobbit (Spiertz&vandeHaar,1978).
300kg.ha-1d" 1
.oadditional-N
o1974
»1972
'200kg.ha-\d"1
_i
i
i
v. I
i
15/6 25/6 5/7 15/7 25/7
l
I
I
i
i
i
US U / 8 dates
Fig.3.Patterns andrates ofgrain growth fordifferent climatic conditions insuccessive
yearswith thecultivarLely atoptimal nitrogen dressings.
19
days
50
40
^*t=600
30
20
10115 16171819202122
temperature°C
Fig. 4A.Relationshipbetweenthe
growth.rateperunitlightenergy
(ug.J )andthemeandailytemperature(C)duringthelinearphaseof
grainfilling.
15 16 17 18 19 20 21 22
temperature °C
Fig. 4B.Relationshipbetweenthe
duration (days)fromanthesisto
ripenessandthemeandailytemperature(C)duringthisperiod.It=
sumofmeandailytemperatures ( C.d).
Durationofgraingrowthisrelatedtosenescenceofvegetativeorgansaswellasto
maturationofthegrains.Theearliersenescenceofthegreenorgansofthewheatplantat
hightemperaturescanberetardedbylatenitrogendressings.Inafieldexperiment
(Spiertz&vandeHaar,1978)cropphotosynthesisaftermid-kernelfillingdeclinedmuch
moreslowlywithanadditionalnitrogendressingatthebootstage.Prolongedphotosyntheticproductioncanfavourgraingrowthconsiderably (Ellen&Spiertz,1975).Thesupply
ofassimilatesisgenerallylimitingattheendofthekernelfillingifgrainnumberis
2
adequate (>20000perm ) .Theeffectoflatenitrogendressingsonthefunctioningofthe
leavesindicatesthatafastsenescencecanalsobecausedbyanegativebalancebetween
thenitrogenuptakeoftheplantandtherequirementsofthegrains.Onemightconclude
thatathightemperaturestherapidsenescenceofgreentissuecausesashortageofcarbohydrates,whichcanreducethegrowthrateandevenstopgraingrowthtowardstheendof
thekernel-fillingperiod.Atlowertemperaturesunderoptimalwaterandnutrientsupply
maturationoftheearoftenprecededthesenescenceofgreenorgansandothervegetative
tissue (Spiertz,1977;Sofieldetal., 1977a).
FromstudiesbyJenner&Rathjen (1975,1977),itwasconcludedthatthedevelopmentalpatternofgraingrowthisdeterminedinternallybymetabolicprocessesratherthan
20
TT'
externally bythesupplyofsucroseandaminoacids fromtherestoftheplant.Theyfound
from C-studies thattherateofstarchproduction intheculturedendospermrosetoamaximum
atabout themid-point ofgraindevelopment andthenfellprogressively tönear zero.Other v
researchworkersstudiedtherelationship betweengrainwater contentandthecessation of
graingrowth (Geslin&Jonard, 1948;Andersen etal., 1978).
Itwasshownthat thisrelationshipwasaffectedbytheabscisicacid (AM) concentrationinthewheatgrains.Radley (1976)andKing (1976)foundthatthewater lossof
thegrainsisprecededbyanincrease intheABA-concentration. Application ofABAtothe
earhadnoeffectontherateofgraingrowthbut resulted inanearliercessationof
•,
graingrowthandhastened thedrying ofthegrain.Goldbach (1975)foundthat temperatures
of 26°Ccomparedwith 18°Caccelerated theincrease inABA-concentrationup tothestart
ofripening.LateapplicationofnitrogendecreasedABA-concentration. However,itis
important toknowwhether thefall intheamount ofwater inthegrainandriseofthe
ABA-concentrationatmaturity causedorwasaconsequence ofthecessationofgraingrowth.
Sofieldetal. (1977b)foundnoevidenceofan increased rateofwater lossby the
grainatthestageofmaximum graindryweight.Theysuggested that therapid fall in<
watercontent atthecessationofgraingrowthwasdue toablockage ofthechalaxal zone
ofentry intothegrainbydepositionof lipids.This suggestionagreeswiththefinding
ofJennings &Morton (1963)that lipidcontent increasedaswheat grainsreachedmaturity.
'
Althoughthecontrolling factorsofthecessation ofgraingrowtharenot completely
understood, thestrongdependence oftheduration ofgraingrowthontemperature often
limitsgrainyield. It»maybeworthwhile tolookforgeneticvariability inthis character.
3.3 ASSIMILATIONANDUTILIZATION OF CARBOHYDRATESANDNITROGEN COMPOUNDS
Thetwomainorganic storageproducts inthewheatplantarecarbohydrates andnitrogencompounds.Bothhaveadynamicpatternofassimilation,distribution, relocation and
storage.Themassfractionsofwater-soluble carbohydrates (w.s.c), starchandnitrogen
weredetermined intheyariouspartsofthewheat culmofplantsgrowneither inthephytotronOrinthefield.Althoughcarbohydrate andnitrogenmetabolism arepartly interrelated,
theywillbediscussed sequentially.
Accumulationof carbohydrates
inthevegetative organsofthewheatplant isgoverned
by thebalancebetweenphotosyntheticproductionandtheutilizationofassimilates for
growthandrespiration.When there isasurplusofcarbohydrates,thesearemainly stored
inthestem (Spiertz, 1974).Lowtemperatures andhigh light intensities increased the
carbohydratecontentofallpartsoftheplant.Undertheseartificialclimatic conditions
themassfractionw.s.c.inthestemwasraised toa levelhigherthan0.4 (401)until 4
weeks afteranthesis (Spiertz, 1977).Thew.s.c.-mass fractionofleavesandroots showed
anincreaseasrateofgraingrowthdeclined.Withhightemperaturesw.s.c.-massfractions
decreased shortlyafteranthesis.
Alsounderfieldconditionshighw.s.c.-contents were foundinthestemup toa fortnightafteranthesisunderthebrightconditionsof 1976aswellaswiththecoolovercast
weatherof 1977 (Spiertz&Ellen, 1978;Spiertz &vandeHaar, 1978).Theseresults indicatethattemperature governs indirectly,bytherateofinitial graingrowth,alsothe
21
utilizationofthestemreserves.In1976,ahighlevelofradiationincreasedw.s.c-contentofthestembeforeanthesis,butdecreaseditafteranthesismainlybecauseof
rapidgraingrowthduetothehightemperature.In1977,lowtemperaturesafteranthesis
retardedgraingrowthandobviouslykeptrespirationatalowerlevel,sothatthemass
fractionofw.s.c.inthestemremainedrelativelyhigh.Gifford (1977)concludedthatthe
wheatcropadjustsyieldcomponentsandpossiblydurationofgrainfillingtogivenear
constancyofkernelweightindifferentphotosyntheticenvironments.Theadaptationmechanismsforregulatinggrainsetandgraingrowtharestillincompletelyunderstood.
Formanyyearstherehasbeencontroversyabouttowhatextentthecarbohydrate
producedbyphotosynthesisbeforeanthesiscontributestothegrainyieldofcereals.
Evans&Wardlaw(1976)concludedthatreservesdocontributetograinyieldtoanextent
thatdependsonthetypeofcerealandtheenvironmentalconditions.Reservesofassimilatepresentatfloweringandavailableforlatertranslocationtothegrainscouldbuffer
graingrowthagainstenvironmentalstressesduringgrainfilling.Estimatesofthecontributionofstemreservestograinyieldarederivedfromchangesinstemweightafter
anthesis (Gallagheretal.,1976)orfrom Cstudiesinwholewheatplants (Austinetal.,
1977)andinlabellingonlyspecificorgans (Pearmanetal., 1978).Thepre-anthesis
assimilatecontributionwasestimatedtobenomorethan20°s(Stoy,1963;Thorne,1966;
Birecka&Dakic-Wlodkowska,1966).Laterexperimentsgaveestimatesrangingfrom27%
(Rawson&Evans,1971)to57°6 (Gallagheretal.,1976)ofthegraindrymatteryieldin
wheat.ThelatterpercentagewascriticizedbyBidingeretal. (1977).Theseauthors
carriedoutfieldexperimentswithinsitulabellingofthewholecropcanopywith CCL
atfrequentintervalsbeforeandafteranthesis.Theyfounda121(irrigatedcrops)and
22?o(droughtedcrops)contributionbypre-anthesisassimilates,mainlyfromstemreserves,
tothegraindrymatteryield.Basedonchangesindryweightofthestemafteranthesis
andcorrectionsforlossesduetorespirationandtranslocationtotheroots,wefound
thatthedrymattercontributionofstemreservesrangedfrom760to1360kg.ha" ,which
correspondedto9.0and21.3°&ofthefinalgraindrymatteryieldwithnitrogendressings
of200and50kg.ha",respectively (Spiertz&Ellen,1978).Thelargestpartofstem
weightlosseswasduetoasharpdeclineoftheamountofwater-solublecarbohydrates.The
remainingproportionofdryweightlossesmaybecausedbyrelocationofvariousother
compounds (aminoacids,organicacids,nutrients)andtoasmallextentbylignification
processes.
Austinetal. (1977)foundthatphotosynthesisduringthe18daysfollowinganthesis
contributedonaverage481ofthefinalgraindryweight.Ofthisquantity,abouthalfwas
translocatedtothegrainswithin10daysofinitialassimilation.Theremainderappeared
tobestoredtemporarilyinthestemsandleavesandwastranslocatedtothegrainsfrom
4weeksafteranthesisonwards.Theseauthorsalsofoundthatrelocationofdrymatter
fromthevegetativeorganstothegrainswasgreatestingenotypeswhichlostmostdry
weightofstemsandleaves.Thephenomenonofasurplusofassimilatesduringthefirst
weeksafteranthesiswasalsoobservedinourexperiments (Spiertz&vandeHaar,1978).
Differencesbetweenasemi-dwarfandastandardcultivarwere,however,morepronounced
instemandearweightatanthesisthanindryweightlossofthestemduringgrain
14
filling.Thisfindingisconfirmedby C-studiesofMakungaetal. (1978);theysuggest
22
thatthelowerstemweightofsemi-dwarfcultivarsisamoreimportantcauseofdifferences
inharvestindexthanthegreatermovementofpost-anthesisphotosynthatatothegrain.
Cultivarswithmoregrainsperearhadlargerearweightsatanthesisandincorporated
more Cintotheearbeforeanthesisduringfloretdifferentiation.Ruckenbauer (1975)
foundthatmore CreachedtheearofMarisHobbitthanthatofMarisHuntsman,but
Hobbithadalsomoregrainsperear.
Consideringthefunctionofleavesinassimilatedistributionandutilizationofthey
plant, nitrogen eompmmds playacomplexrole.ReferringtothemodelproposedbyThornley
(1977)nitrogencompoundscanbedividedintothreecategories: (1)storagematerial
(2)biologicallyactivematerial,(3)inertmaterial.Nitrogencompoundsaccumulatedand
storedinthegreenorgansofthewheatplant,especiallytheleaves (bladeandsheath)
areusuallythemainnitrogensourceforthegrowinggrains (Nairetal., 1978).Atthe
sametimesomenitrogencompoundsarebiologicallyactiveanddeterminetheactivityand
durationofphysiologicalprocesses,viz.photosynthesisandnitrateassimilation.
.Inourexperimentsinthephytotronaswellasinfieldexperimentswefoundthat
hightemperaturesraisedtherateofnitrogenuptakebythegrainsmorethanthecarbohydrateaccumulation (Spiertz,1977;Spiertz&Ellen,1978).Sowarmthduringthegrain-fillingperiodpromotedthenitrogenmassfractionofthegrain.Alreadyin1914LeClerc
&Yoderdemonstratedwiththeircurioustri-localsoil-exchangeexperimentthatclimate
hasamuchgreaterinfluenceontheproteincontentofwheatgrainthansoilfertility.
UndercontrolledenvironmentalconditionsCampbell&Read (1968)foundthatincreasing M . ,
eitherdaytemperature (from21to27°C)ornighttemperature (from13to21°C)raised JJII
theproteincontentofthegrain.Therewereonlysmallinteractionswithlightintensity
andsoilmoisturestress.Itwasstatedthatreducedlightintensitylowersthegrain
«e/Ui*,
nitrogencontenttoaboutthesameextentasgrainweight,withtheresultthatthemass
fractionofnitrogenislittleaffected (Bremner,1972).However,inourphytotronexperiment (Spiertz,1977)andintheexperimentsofKolderup (1975)andSofieldetal. (1977bl
therewasalsoaclearinverserelationbetweenlightintensityandthemassfractionof
nitrogeninthegrain.Strikingwastheweakresponseofnitrogenyieldanddistribution
ofnitrogentoenvironmentalconditions.Obviously,nitrogeneconomyismoreundergenetic
controlthancarbohydrateeconomy;thelatterseemstoreflectthephotosyntheticconditions.
Inthephytotronexperimentwithregularnitrogensupplytotheplants,about65%of
thegrainnitrogenwasderivedfromthevegetativeaerialparts,whilst35%wasuptake
fromtherootsorthesoilafteranthesis.Theseproportionscorrespondwithdataof
Deherain&Dupont (1902).InourfieldexperimentswithlateNapplications,wefound
about50%(100kg.ha )ofthenitrogenuptakeafteranthesisinthelessleafycropof
1976 (Spiertz&Ellen,1978)andabout 20%(25kg.ha- )inthecropswithanearlyvigorous
developmentin1977.Austinetal. (1977)andPearmanetal. (1977)reportedforBritish
growingconditionsthatpost-anthesisnitrogenuptakeaccountedforonly17%and15to28%,
respectively.Thepost-anthesisnitrogenuptakeisstronglyaffectedbyrootactivity,
moisturelevelandnitrogensupply,asshownbyextensivestudiesofCampbelletal.
(1977a,b)andCampbell&Paul (1978).
23
Alatenitrogendressingatthebootstagetoacropwithanintermediateplantdensityturnedouttofavourgrainnumberaswellassupplyofassimilatestothegrains
(Spiertz&Ellen,1978;Spiertz&vandeHaar,1978).Thelatterwasduetoaretarded
depletionofthenitrogencontentinthegreenorgansofthewheatplantandaprolonged
photosyntheticcapacity.Supplywithnitrogencompoundswasmorefavouredthancarbohydrate
supplytothegrains.Thereforenitrogenharvestindex (percentagegrainnitrogen)was
raisedfrom0.75to0.81 andfrom0.74to0.79 intheyears1976and1977,respectively.
ThisefficiencyofnitrogendistributionwasalsofoundbyDallingetal. (1976),whilst
Austinetal. (1977)reportedanitrogenharvestindexof0.68asanaveragevaluefor
variousgenotypes.Canvin(1976)statedthatnitrogenharvestindexisnotaconstant
featureofacultivarandthatthereisasmuchvariationwithinacultivarasthereis
betweencultivars.
3.4 AGRONOMICPOSSIBILITIESANDLIMITATIONSFORINCREASINGGRAINYIELD
Discussionsofwhetherassimilatesupply (=source)orstoragecapacity (=sink)
limitsyieldrefermostlytothegrain-fillingstage,sincemostgraingrowthissupported
byconcurrentphotosynthesisratherthanbystoredreservesofcarbohydrate (seeSection
3.3).However,thesinkorstoragecapacityforassimilatesatthegrainfillingstageis
toalargedegreedeterminedbytheextentofphotosynthesis,nitrogenassimilationand
drymatterdistributionbeforeanthesis,especiallyfromearinitiationonwards (seeSection3.2).Thus,whethersourceorsinklimitsgraindevelopmentdependsonthebalance
betweengrowthanddevelopmentofthecropduringthevariousstagesofthelifecycle.
Productivecultivarsareadaptedtothegrowingconditionsinsuchawaythattheirproductionpatternhasalargepotentialformaximizingtheutilizationofirradianceandthe
storageofphotosynthatesinthegrain.
ThecomparisonofgrainnumbersandgrainyieldsofthecultivarLely (Fig.1)in
variousseasonsshowedthat,undergrowingconditionsintheNetherlandswithdisease-free
crops,grainnumberperunitgroundareaismostlylimiting.Thisrelationshipsuggests
thatforachievingtopyieldsagrainnumberperm ofabout20000isrequired.Darwinkel
2
(1978)foundaminimumvalueof18000grainsperm ,butthisfigurewasestablished
underthepoorlightconditionsof1977.Underhighirradiationincontrolledenvironments
withmicro-cropsEvans(1978)foundalinearrelationshipbetweengrainnumberandgrain
2
yieldupto28600grainsperm.
Grainnumberperear (andperunitgroundarea)dependsgreatlyontheavailability
ofassimilates,butalsoonthedistributionwithintheshoot.Itwasshown(seeSection
3.3)thatthereexistgenotypicdifferencesinsink-strengthofthedevelopingear,which
arereflectedinahigherearweightandalowerstemweightatanthesis.Thistrendhas
beenpresentalreadyformanyyearsinDutchcultivars,asillustratedbythedrymatter
distributioninthecultivarsJulianaandLely (Kramer,1978).Ourownresultsandthe
resultsofcurrentresearchinEnglandindicatethatfurtherprogresswithsemiortriple
dwarftypesispossible.
24
T
Anotherapproachtoincreasethenumberofgrainsperearwasoutlined"byDonald (1968)
inhisconceptofawheatideotype:singleculm,strongstem,dwarfstatureandlargespike.
ThefirstuniculmtypeofwheatwascrossedinIsrael.Atsmon&Jacobs (1977)reportedan
averagegrainnumberperearof106withinarangefrom80to 180.Thesehugenumbersof
grainswereduetoahighernumberofgrainsperspikeletandmorespikeletsperear.The
highgrainnumberperearwasassociatedwithanaveragegraindrymatterweightof'62.5mg
perkernelandagraindrymatteryieldperplantof4.4g.However,vegetativepartswere
robustandvigorous,includingbroad,thick,darlcgreenleavesandthick,stiffstraw.The
largerandproliferousearhadaconsiderablyhigherchaffweight.Thisuniculmfulfils
onlypartofDonald'sconceptoftheideotype,becauseitisnotaweakcompetitorand
Ultimatelysensitivetomutuallightcompetition.Agronomically itisquestionablewhether
a lowplantdensitywithlargeearsismorefavourablethanadensecropwithsmallerears
ifgrainnumberperunitgroundareaisequal.Furtherthelackoftilleringcapacitymay
beadisadvantageofwinterwheatunderpoororvariableestablishmentconditions.
Assumingthatgrainnumberperunitgroundareacanbeincreased,thentheincreased
demandforassimilatesmustbeconsidered.Hightemperaturesenhancetheconversionof
precursors (sucroseandaminoacids)intostorageproducts (starchandprotein)inthe
grain,butalsotherateofrespiration (Spiertz,1977;Apel&Tschäpe,1973).Underthese
growingconditionstheutilizationofassimilatescanbegreaterthancurrentphotosynthesisandnitrogenassimilation (Spiertz&Ellen, 1978).Thedemandsforcarbohydratesare
bufferedbythestemreserves,buthighrequirementsfornitrogenwouldacceleratesenescenceandshortenthegrain-fillingperiod (Fig. 5 ) .
AsphotosynthesisdependsonsolarradiationandambientGCL-concentration,thereis
noevidenceforaconsiderableincreaseofnetcropphotosynthesis.Sibma (1977)inferred
fromacomparisonbetweenpotentialgrossproductionandcropgrowthratederivedfrom
lightinterceptionthatphotosyntheticproductionofwheatcanbeincreasedbyprolonging
thegrowthperiod.Ifwaterisavailableadditionalnitrogendressingsatthebootstage
andadequatediseasecontrolfavournetphotosynthesisattheendofthegrowingperiod
(Spiertz,1973;Ellen&Spiertz,1975;Spiertz&vandeHaar, 1978).However,ithas
alreadybeenobservedthatinthefieldtheearssometimesmaturebeforethevegetative
organssenesce.
Highgrainyield,associatedifpossiblewithahighcontentofgrainprotein,
requireseitherlargenitrogenreservesinthevegetativeorgansoracontinueduptakeof
nitrogenafteranthesis.Assumingasagoal 10tonsofgraindrymatterperhawitha
nitrogenmassfractionof0.025 (2.5%),thenanitrogensupplyof250kg.ha" isrequired.
Normallyinagoodwinterwheatcrop,nitrogenyieldatanthesisamountstoabout 150kg.
1
•
-1
ha ofwhichabout 100kg.ha isavailableforrelocationtothegrains (Cole,1960;
Spiertz&Ellen,1978). Soalargequantityofnitrogenmustbeabsorbedandassimilated
afteranthesis;thisabsorptionalsoneedsaprolongedactivityoftheroots.
,Uptonowmostlypotentialgrainyieldsofwheathavebeencalculatedfromthephotosyntheticpotentials (deWit,1965;Evans,1970).Theconsequencesofthesepotential
yieldsforthenitrogeneconomyofthewheatplantaremostlyoverlooked.Themajorityof
thestudiesonnitrogeninthewheatplantconcernthenitrogencontentofthegrainand
25
genotype
environment
accumulation
Fig. 5.Modeloffactorsandprocessesrelatedtograingrowthofwheat.en,cropcomponents;
Q ,processes; C 3 ,environmentalfactors; ,dependenceon;— y , directeffect;-v.>,indirecteffect;—•,directrelation;—>,indirectrelation.
notthenitrogeneconomyofthewholeplant.Furtherresearchonachievinghighergrain
yieldshastoconsidernotonlyphotosyntheticproductionbutalsonitrogeneconomyand
rootactivity.
Thegapbetweenactualandpotentialgrainyieldhasbeennarrowedinthepastby
providingbettergrowingconditionsthroughimprovedcultivationmethods,suchasfertilizerapplication,weedcontrol,soiltillage,irrigation,etc.Inthelastdecadethe
applicationoffungicides,whengeneticdisease-resistancefailed,contributedtostill
higherandmorestablegrainyields.Furtherprogresshastobemadebypreventingdamages
throughpathogensoftheroots.
Improvementofgrowingconditionsandofgenotypeswillleadtohigherandmore
stablegrainyieldsofwheatandasaresulttoabetteruseofsolarenergyandofthe
availablelandacreage.
26
T-—
3.5 REFERENCES
Andersen,K.,Chr.P.Lysgaard&S.Andersen,1978.Increaseindryweightandnitrogen
contentinbarleyvarietiesgrownatdifferenttemperatures. Acta agrio. Soand. 28:
90-96.
Apel,P.&M.Tschäpe,1973.DieÄhrenatmunginderPhasederKornfüllungbeiWeizen
(TriticumaestivumL.). Bioohem. Physiol. Pflanz. 164:266-275.
Atsmon,B.&E.Jacobs,1977.Anewlybred 'Gigas'formofbreadwheat (Triticumaestivum
L.):morphologicalfeaturesandthermo-photoperiodicresponses. Crop Soi. J7:31-35.
Austin,R.B.,i.A.Edrich,M.A.Ford &R.D.Blackwell,1977.Thefateofthedrymatter,
carbohydratesand Clostfromtheleavesandstemsofwheatduringgrainfilling.
Ann. Bot. 41:1309-1321.
Bidinger,F.,R.B.Musgrave&R.A.Fischer,1977.Contributionofstoredpre-anthesis
assimilatetograinyieldinwheatandbarley. Nature 270:431-433.
Birecka,H.&L.Dakic-Wlodkowska,1966.Photosyntheticactivityandproductivitybefore
andafterearemergenceinspringwheat. Acta Soo. Bot. Pol. 35:637-662.
Biscoe,P.V.&J.N.Gallagher,1977.Weather,drymatterproductionandyield.In:
J.J.Landsberg &C.V.Cutting (Eds),EnvironmentaleffectsonCropPhysiology.
AcademicPress,NewYork,London,75-100.
Bremner,P.M., 1972.Accumulationofdrymatterandnitrogenbygrainsindifferentpositionsofthewheatearasinfluencedbyshadinganddefoliation. Aust. J. biol.
Soi.
25:657-668.
Bremner,P.M.&H.M.Rawson,1978.Theweightsofindividualgrainsofthewheatearin
relationtotheirgrowthpotential,thesupplyofassimilateandinteractionbetween
grains.Aust. J. PI. Physiol. 5:61-72.
Campbell,C A . ,D.R.Cameron,W.Nicholaichuk&H.R.Davidson,1977a.Effectsoffertilizer
N,andsoilmoistureongrowth,Ncontentandmoistureusebyspringwheat. Can. J.
Soil Soi. 57: 289-310.
Campbell,C A . ,H.R.Davidson&F.G.Warder,1977b.EffectsoffertilizerNandsoil
moistureonyield,yieldcomponents,proteincontentandNaccumulationintheabovegroundpart&ofspringwheat. Can. J. Soil Soi. 57:311-327.
Campbell,C A . &E.A.Paul,1978.EffectsoffertilizerNandsoilmoistureonmineralization,N-recoveryandA-valuesunderspringwheatgrowninsmalllysimeters. Can. J.
Soil Soi. 58:39-51.
Campbell,C A . &D.W.L.Read,1968.Influencesofairtemperature,lightintensityand
soilmoistureonthegrowth,yieldandsomegrowthanalysescharacteristicsof
Chinookwheatgrowninthegrowthchamber. Can. J. PI. Soi. 48:299-311.
Canvin,D.T.,1976.Interrelationshipsbetweencarbohydrateandnitrogenmetabolism.In:
Geneticimprovementofseedproteins.NationalAcademyofSciences,WashingtonD.C.,
172-190.
Chowdhury,S.I.&I.F.Wardlaw,1978.Theeffectoftemperatureonkerneldevelopmentin
cereals.Aust. J. agrio. Bes. 29: 205-223.
Coïc,Y.,1960.Lesbasesphysiologiquesdelanutritionetdelafertilisationrationelle
dublë.In:ProgressiveWheatProduction,Centred'Etudedel'Azote,4,Geneva,95-116.
Dalling,M.J.,G.Boland&J.H.Wilson,1976.Relationbetweenacidproteinaseactivity
andre-distributionofnitrogenduringgraindevelopment inwheat. Aust. J. Pi.
Physiol. 3:721-730.
Darwinkel,A.,1978.Patternsoftilleringandgrainproductionofwinterwheatatawide
rangeofplantdensities. Neth. J. agrio. Soi. 26 (inpress).
Deherain,P.P.&C.Dupont,1902.Surl'originedel'amidondugraindeblë. Annls agron.
28:522-527.
Donald,C M . , 1968.Thebreedingofcropideotypes. Euphytioa 17:385-403.
Ellen,J. &J.H.J.Spiertz,1975.Theinfluenceofnitrogenandbenlateonleaf-areaduration,graingrowthandpatternofN-,P-andK-uptakeofwinterwheat (Triticumaesti-
vum). Z. Acker- u. PflBau 141: 231-239.
Evans,L.T.,1978.Theinfluenceofirradiancebeforeandafteranthesisongrainyieldand
itscomponentsinmicrocropsofwheatgrowninaconstantdaylengthandtemperature
regime.Fid Crops Bes. 1:5-19.
Evans,L.T.&I.F.Wardlaw,1976.Aspectsofthecomparativephysiologyofgrainyieldin
cereals. Adv. Agron. 28:301-359.
Evans,L.T.,I.F.Wardlaw&R.A.Fischer,1975.Wheat.In:L.T.Evans (Ed),CropPhysiology:somecasehistories.CambridgeUniversityPress,101-149.
Evans,L.T.&H.M.Rawson,1970.Photosynthesisandrespirationbytheflagleafandcomponentsoftheearduringgraindevelopmentinwheat. Aust. J. biol. Soi. 23:245-254,
Fischer,R.A., 1975.Yieldpotentialinadwarfspringwheatandtheeffectofshading.
Crop Soi. 15: 607-613.
27
Fischer,R.A.,I.Aquilar&D.R.Laing,1977.Post-anthesissinksizeinahigh-yielding
dwarfwheat:yieldresponsetograinnumber. Aust. J. agric. Res. (28)2:165-176.
Fischer,R.A.&G.W.Kohn,1966.Therelationshipofgrainyield tovegetativegrowthand
postfloweringleaf-areainthewheatcropunderconditionsoflimited soilmoisture.
Aust. J. agric. Res. 17:281-295.
Ford,M.A.&G.N.Thorne,1975.Effectsofvariationintemperatureandlightintensity
atdifferenttimesongrowthandyieldofspringwheat. Ann. appl. Biol. 80:283-299.
Gallagher,J.N.,P.V.Biscoe&B.Hunter,1976.Effectsofdroughtongraingrowth.
nature 264:541-542.
Geslin,H.&J.Jonard,1948.Maturationdubléetclimat. Ann. Nutr. Alim. 2:111-121.
Gifford,R.M., 1977.Growthpattern,carbondioxydeexchangeanddryweightdistribution
inwheatgrowingunderdifferingphotosyntheticenvironments. Aust. J. Pi.
Physiol.
4:99-110.
Goldbach,H.,1975.TheabscisicacidcontentofripeninggrainsofvariousbarleycultivarsinrelationtotemperatureandN-nutrition.Thesis,UniversitätHohenheim,
Stuttgart.
Hsu,P.SP.D.Walton,1971.Relationshipbetweenyieldanditscomponentsandstructures
abovetheflag-leafnodeinspringwheat. Crop Sei. 11:190-193.
Jenner,C.F.&A.J.Rathjen,1975.Factorsregulatingtheaccumulationofstarchin
ripeningwheatgrain. Aust. J. PI. Physiol. 2:311-322.
Jenner,C.F.&A.J.Rathjen,1977.Supplyofsucroseand itsmetabolism indeveloping
grainsofwheat. Aust. J. PI. Physiol. 4:691-701.
Jennings,A.C.&R.K.Morton,1963.Changesinnucleicacidsandotherphosphoruscontainingcompoundsofdevelopingwheatgrain. Aust. J. hiol. Sei. 16:332-341.
King,R.W., 1976.Abscisicacidindevelopingwheatgrainsand itsrelationship tograin
growthandmaturation. Planta 132,1:43-51.
Kolderup,F., 1975.Effectofsoilmoisture,airhumidityand temperatureonseedsetting
andearsizeinwheat. Acta agric. Scand. 25:97-102.
Kramer,Th.,1978.Mogelijkhedentotverbeteringvandestikstofbenuttingdoorplantenveredeling. Landbouwk. Tijdschrift
90:24-31.
LeClerc,J.A.&R.A.Yoder,1914.Environmentalinfluencesonthephysicalandchemical
characteristicsofwheat. J. agric. Res. 1:275-291.
Ledent,J.F.,1977a.Relationsentrerendementparépietcaractèresmorphologiquesà
maturitéchezdiversesvariétésdebléd'hiver (Triticumaestivum L.). Annls Agron.
(28)4:391-407.
Ledent,J.F., 1977b.Effectofpartialdefoliationandveincuttingongraingrowthand
yield inwinterwheat (Triticumaestivum L.). Bull. Soc. r. Bot. Belg. 110:239-250.
Makunga,O.H.D.,I.Pearman,S.M.Thomas &G.N.Thorne,1978.Distributionofphotosynthate
producedbeforeandafteranthesisintallandsemi-dwarfwinterwheat,asaffected
bynitrogenfertilizer. Ann. appl. Biol. 88:429-437.
Marcellos,H.&W.V.Single,1972.Theinfluenceofcultivar,temperatureandphotoperiod
onpost-floweringdevelopmentofwheat. Aust. J. agric. Res. 23:533-540.
McNeal,F.H.&M.A.Berg,1977.Flagleafareainfivespringwheatcrossesandthe
relationship tograinyield. Euphytica 26:739-744.
Meredith,P.&L.D.Jenkins,1976.Thedevelopingstarchgranule.3.Thefillingofthe
wheatgrain. N.Z. Jl. Sei. 19:115-123.
Nair,T.V.R.,H.L.Grover&Y.P.Abrol, 1978.Nitrogenmetabolismoftheupper threeleaf
bladesofwheatatdifferentsoilnitrogenlevels. Physiologia PI. 42:293-300.
Osman,A.M.,1971.Drymatterproductionofawheatcropinrelationtolightinterception
andphotosyntheticcapacityofleaves. Ann. Bot. 35:1017-1035.
Pearman,I.,S.M.Thomas&G.N.Thorne,1977.Effectsofnitrogenfertilizerongrowthand
yieldofspringwheat. Ann. Bot. 41:93-108.
Pearman,I.,S.M.Thomas&G.N.Thorne,1978.Effectsofnitrogenfertilizeronthedistributionofphotosyntateduringgraingrowthofspringwheat. Ann. Bot. 42:91-99.
Pinthus,M.J. &Y.Sar-Shalom,1978.Drymatteraccumulationinthegrainsofwheat (TriticumaestivumL.)cultivarsdifferingingrainweight. Ann. Bot. 42:469-471.
Puckridge,D.W.&D.A.Ratkowsky,1971.Photosynthesisofwheatunder fieldconditions.
IV.Theinfluenceofdensityand leafareaindexontheresponsetoradiation.
Aust. J. agrie. Res. 22:11-20.
Radley,M.,1976.Thedevelopmentofwheatgraininrelationtoendogenousgrowthsubstances. J. exp. Bot. 27:1009-1021.
Rawson,H.M. &L.T.Evans,1971.Thecontributionofstemreserves tograindevelopment
inarangeofwheatcultivarsofdifferentheight. Aust. J. agrie. Res. 22:851-863.
Ruckenbauer,P., 1975.Photosyntheticand translocationpatternincontrastingwinter
wheatvarieties. Ann. appl. Biol. 79:351-359.
28
Sibma, L., 1977.Maximization ofarable crop yields in theNetherlands, f / e t h . J.
agvio.
Soi. 25:278-287.
Simpson, G.M., 1968.Association between grain yield perplant andphotosynthetic area
above theflag-leaf node inwheat. Can. J. PI. Soi. 4 8 :253-260.
Sofield, 1.,L.T. Evans, M.G. Cook &X.F. Wardlaw, 1977a. Factors influencing therateand
duration ofgrain filling inwheat. Auat. J. PI. Physiol.
4:785-797.
Sofield, I.,L.T. Evans &I.F.Wardlaw, 1974.Theeffects oftemperature andlighton
grain filling inwheat. Bull. ft. Soo. N.Z. 12:909-915.
Sofield, I.,I.F.Wardlaw, L.T. Evans & S.Y. Zee,1977b. Nitrogen, phosphorus andwater
contents during grain development andmaturation inwheat, kust. J. PI.
Physiol.
4: 799-810.
Spiertz, J.H.J., 1973. Effects ofsuccessive applications ofmaneb andbenomyl on growth
and yield offive wheat varieties ofdifferent heights. Neth. J. agvio.
Soi. 21:
282-296.
Spiertz, J.H.J., 1974. Grain growth anddistribution ofdrymatter inthewheat plantas
influenced bytemperature, light energy andearsize. Neth. J. agvio.
Soi. 2 2 :207-220.
Spiertz, J.H.J., 1977.Theinfluence oftemperature andlight intensity ongrain growthin
relation tothecarbohydrate andnitrogen economy ofthewheat plant. Neth. J.
agvio.
Soi. 25:182-197.
Spiertz, J.H.J.&J.Ellen, 1978. Effects ofnitrogen oncrop development andgrain growth
of winter wheat inrelation toassimilation andutilization ofassimilatesand
nutrients. Neth. J. agvio. Soi. 26: 210-231.
Spiertz, J.H.J.&H.vandeHaar, 1978. Cultivar differences andnitrogen effects ongrain
yield, crop photosynthesis anddistribution ofassimilates inwinter wheat. Neth. J.
agvio. Soi. 26:233-249.
Spiertz, J.H.J.,B.A.tenHag&L.J.P. Kupers, 1971. Relation between green area duration
and grain yield insome varieties,of spring wheat. Neth. J. agvio.
Soi. 19:211-222.
Stoy,V.,1963.Thetranslocation of C-labelled photosynthetic products from theleaf
to theearinwheat. Physiologia
PI. 16: 851-866.
T h o m e , G.N., 1966. Physiological aspects ofgrain yield incereals. In:F.L. MiIthorpe&
J.D. Ivins (Eds), TheGrowth ofCereals andGrasses. Butterworth, London, 88-105.
Thorne, G.N. &J.C. Blacklock, 1971. Effects ofplant density andnitrogen fertilizeron
growth andyield ofshort varieties ofwheat derived from Norin 10. Ann. appl.
Biol.
68: 93-111.
Thorne, G.N., P.J.Welbank &G.C. Blackwood, 1969. Growth andyield ofsixshort varieties
of spring wheat derived from Norin 10andoftwoEuropean varieties. Ann. appl.
Biol.
63: 241-251.
Thornley, J.H.M., 1977. Growth, maintenance andrespiration: are-interpretation. Aren. Bot.
41: 1191-1203.
Walpole,P.R.&D.G. Morgan, 1974.Theinfluence ofleaf removal upon thedevelopmentof
the grain ofwinter wheat. Ann. Bot. 38:779-782.
Warrington, I.J.,R.L. Dunstone &L.M. Green, 1977. Temperature effects atthree development stages ontheyield ofthewheat ear. Auat. J. agvio.
Res. 2 8 :11-27.
Watson, D.J., G.N. Thorne &S.A.W. French, 1963. Analysis ofgrowth andyield ofwinter
and spring wheats. Ann. Bot. 2 7 : 1-22.
Welbank, P.J., S.A.W. French &K.J. Witts, 1966. Dependence ofyields ofwheat varieties
on their leaf-area durations. Ann. Bot. 3 0 :291-299.
Willey, R.W. &R. Holliday, 1971. Plant population, shading andthinning studies inwheat.
J. agvio. Soi., Canto.77: 453-461.
Wit, C T . de,1965. Photosynthesis onleaf canopies. Agvio.
Wageningen,1-57.
Res. Rep. 663, Pudoc,
29
I/
Summary
Them a m purposeofgrowingawheatcrophasalwaysbeentoproducegrain.Finalgrain
2
yieldisafunctionofnumberofearsperm ,numberofgrainsperearandmeanindividual
grainweight.
Sinceresearchworkersfoundthatgraingrowthisbasedlargelyonpost-floralassimilation,muchemphasishasbeengiventothesignificanceofthesizeandthelongevity
ofthephotosyntheticactiveorgansforthegrainyield.Followingtheconceptsaboutleaf
areaindex (LAI)andleafareaduration(LAD)ofWatsonandco-workers,westudiedthe
relationbetweengrainyieldandgreenareadurationofthevariousgreenorgansunder
growingconditionsintheNetherlands.Bymultipleregressionanalysis,upto83% {R)of
thevarianceingrainyieldcouldbeattributedtothevarianceingreenareadurationof
flagleaf,peduncle (incl.leafsheath),ear,penultimateleafandlastinternode.From
thesecalculationsitcouldbederivedthattheareadurationsofflagleafandpeduncle
weremoststronglyassociatedwithgrainyield.However,withinawheatplantthereisa
highdegreeofco-variationbetween,thegreenareadurationsofindividualorgans,sothat
itwasnotpossibletoestimatetheexactcontributionoftheseorganstograingrowth.
Evenwithahighcorrelationbetweengreenareadurationandgrainyield,itisnotpossible
todeterminewhethergraingrowthisdirectlyaffectedbyenvironmentalconditionsorindirectlythroughthesupplyofassimilatesbythevegetative (green)partsoftheplant.
Thereforetheeffectsoflightintensityandtemperatureonthedurationandrateof
graingrowthandontheassimilationandutilizationofphotosynthateswerestudiedin
phytotronexperiments.Hightemperaturesconsiderablyincreasedtherateofgraingrowth,
butlikewiseshortenedthedurationofgraingrowth.Thusthedailyrequirementsofthe
grainsforassimilatesincreasedwithariseintemperature.Asgraingrowthissustained
largelybycurrentphotosynthesis,lightintensityaffectedgrainyieldmoreathighthan
atlowtemperatures.Therestrictedgraingrowthatlowtemperaturesledtoasurplusof
assimilates,whichaccumulatedinthevegetativeorgans;especiallycarbohydrateswere
storedtemporarilyinthestem.
Ahightemperatureduringgrainfillingpromotedtheaccumulationofnitrogeninthe
grainsrelativelymorethanitpromotedthestorageofstarch.Lightintensityhadonlya
minoreffectonnitrogenaccumulationandproteinsynthesisinthegrain.Thechangein
nitrogencontentofthegrainswascausedbytheeffectoflightintensityoncarbohydrate
supply.
Althoughwarmthraisedtherateofnitrogenuptakebythegrainconsiderably,the
nitrogenyieldofthegrainswashardlyaffected.Thisresultindicatesthatwithoutpostfloralnitrogenuptake,thedurationofthegrain-fillingperiodisdeterminedbythe
amountofnitrogenreservesinthewheatculmatanthesisandbytherateofnitrogen
30
relocationfromthevegetativeorgans tothegrains.
Theresponsesofspringwheattotemperatureand lightintensity inthephytotron
werecomparedwiththebehaviourofwinterwheat infieldexperimentsduringfivegrowing
seasons,whichcoveredalargerangeofclimaticconditionsduringthe grain-filling
period.Itwasfoundthatalsounderfieldconditions temperaturewasthemaindeterminant
oftherateofgraingrowthanditsduration.However,temperatureeffectsongrainyield
underfieldconditionsweremasked,duetoco-variationbetween lightintensityandtemperature.Fromthepatternofcarbohydrateaccumulationinthestemandassimilateutilizationbythegrains,itwasconcludedthatgraingrowthduringthefirstthreeweeksofthe
grain-fillingperiodwasmoregovernedbytemperature thanbytheavailabilityofassimilates.Duringthelatterpartofthisperiodadditionalassimilates,madeavailablebya
prolongedphotosyntheticactivity,favouredgraingrowth.
Isuggestedthatunderthegrowingconditionsforwinterwheat intheNetherlands the
storagecapacityofthegrainsislimitingduring thefirstweeksafteranthesis (sinklimitation),whilstlateronthesupplyofassimilates tothegrainsmightbe limiting
(source-limitation),duetoconstraints ofwater,nitrogenanddiseases.Bylatenitrogen
applicationsanddiseasecontrolwithfungicides,thelongevityofthephotosynthetic
activeorganscouldbeprolongedandgrainyieldenhanced.A latenitrogenapplication,
however,increasedthenumberofgrainsperear.
Cropperformanceundervariousenvironmentalconditionsdependsondifferencesbetween
cultivars.Therelativeimportanceofvarioustraitsofasemi-dwarfandastandardwheat
cultivarwereassessed.Thehigherharvest-index ofthesemi-dwarfcultivarwasbrought
aboutpartlybyafavouredeargrowthduringtheprefloralperiodandpartlybyafaster
graingrowthduringthefirsthalfofthegrain-fillingperiod.Thesemi-dwarfcultivar
hadareducedstemweight;leafandchaffweightwereaffectedpositively,butonlytoa
smallextent.Therewereonlysmalldifferences innitrogenyieldanddistributionbetween
thecultivars.However,nitrogencontentofthegrainsdiffered stronglyduetodifferences
instarchaccumulation.Thenitrogencontentofthegrainsvariedalsostronglywithina
cultivar:awarmgrowingseasonincreased theproteinmass fraction (upto0.14),whilst a
coolgrowingseasonresulted inalowproteinmassfraction (about0.08).Thenitrogen
harvest-indexdidnotvarywidelybetweenseasonsandcultivars,whensplitnitrogen
dressingswereapplied.This indexrangedfrom0.74 to0.8].
Amuchgreatervariationoccurredbetweenseasons intheamountofnitrogenuptake
afteranthesis;thisamountrangedonaveragebetween 20and50'»ofthefinalgrain-nitrogenyield.Especiallywhenvegetativegrowthwasrestricted,post-floralnitrogenuptake
wasneededtofulfilltherequirementsofthegrainsatahighyield level.A lateuptake
ofnitrogenintheaerialpartsofthewheatculmindicatesnitrogenreserves intheroot
systemoraprolongedactivityoftheroot system.
Theagronomicpossibilities andlimitations forincreasinggrainyieldarediscussed.
Furtherprogressinincreasinggrainyieldhastobemade insuchawaythatthewheat
cropisadaptedasmuchaspossibletotheenvironmentalconditions.Itishypothesized
31
thatfurther increase ingrainyieldmightbeexpected fromahigher grainnumberperunit
ground area,fromalongerrootactivity afteranthesis and fromaprolonged capability of
thegrains toaccumulate assimilatesandconvert these intostorageproducts.
32
Samenvatting
Korrelproduktie en assimilatenhuishoudingbij
weersfaotoren en
stikstofvoorziening
tarwe in relatie
tot
raseigeneahappen,
Hethoofddoelbijdeteeltvantarweissteedsdeproduktievankorrelsgeweest.De
2
korrelopbrengstiseenfunctievanhetaantalarenperm,hetaantalkorrelsperaaren
hetgemiddeldegewichtperkorrel.Sindsdooronderzoekerswerdvastgestelddatdekorrelgroeigrotendeelsafhankelijkisvandepostflorale fotosynthese,iserveelaandachtgegevenaandebetekenisvandegrootteendevlevensduurvandefotosynthetischactieveorganenvoordekorrelopbrengst.
InaansluitingopdeopvattingenvanWatsonenmedewerkers overdebebladerings-index (leafareaindex,LAI)endebebladeringsduur (leafareaduration,LAD)werdde
samenhangtussendekorrelopbrengstenhetindetijdgeïntegreerde groeneoppervlakvan
deafzonderlijkeorganenbestudeerdonderNederlandsegroei-omstandigheden.Doormiddel
2
vanmeervoudigeregressie-analysekontot83$ (R)vandevariatieinkorrelopbrengst toegerekendwordenaandevariatiesindegeïntegreerde groeneoppervlakkenvanhetvlagblad,
deaarsteel,hetvoorlaatstebladeninternodium.Uitdezeanalysekonwordenafgeleiddat
hetvlagbladendeaarsteelhetsterkstgerelateerdwarenaandekorrelopbrengst.Vanwege
dehogematevanco-variantie tussengroeneoppervlakkenvandeindividueleorganenwas
hetnietmogelijkdeexactebijdragevandeafzonderlijke organenteberekenen.Zelfseen
hogecorrelatietussengroenoppervlakenkorrelopbrengst geeftgeenantwoordopdevraag
ofdegroeivandekorrelsdirectwordtbeïnvloeddooruitwendigeomstandighedendanwel
indirectdoordetoevoervandeassimilatenuitdegroeneorganen.
Hiertoewerdendeinvloedenvanlichtentemperatuuropdeduurensnelheidvan
korrelgroeienopdestofwisselingsprocessenindetarweplantbestudeerddoormiddelvan
-fytotronproeven.Hetbleekdathogetemperaturendegroeisnelheidvandekorrelssterk
verhoogden,maartevensdegroeiduurbekortten.Daardoorwerddedagelijksebehoeftevan
dekorrelsaanassimilatenvergrootmethetstijgenvandetemperatuur.Omdatindeassimilatenbehoeftevandekorrelsgrotendeelswordtvoorziendoordefotosynthesetijdensde
korrelvulling,isdehoeveelheid lichtbelangrijkervoordekorrelopbrengstbijhogedan
bijlagetemperaturen.Detragekorrelgroeibijlagetemperaturenveroorzaakte zelfseen
overschotaanassimilaten,dieopgeslagenwerdenindevegetatieveorganen;metnamevond
eropslagvanwater-oplosbare-koolhydratenindestengelplaats.
Hogetemperaturengedurendedekorrelvullingbevorderdendeopslagvanstikstofin
dekorrelsmeerdandetoenamevanzetmeel.Delichtintensiteithadslechtseengering
effectopdestikstofopnameeneiwitsyntheseindekorrel,maarbeïnvloedde desondanks
heteiwitgehaltevandekorreldooreenveranderingvandekoolhydratentoevoernaarde
korrel.Ofschoonhogetemperaturendestikstofopnameindekorrelaanzienlijkversnelden,
werddetotalehoeveelheidstikstofindekorrelsnauwelijksbeïnvloed.Ditduidterop
datbijafwezigheidvanstikstofopnamedoordetarweplantnadebloeideduurvandekorrelvullingmedewordtbepaalddoordestikstofvoorraadindehalmbijdebloeiendoor
33
desnelheidvanherverdelingvanstikstofvanuitdevegetatieveorganennaardekorrel.
Dereactiesvan(zomer-)tarweopvariatiesintemperatuurenlichtintensiteitinhet
fytotronwerdenvergelekenmethetgedragvan (winter-)tarweonderveldomstandighedengedurendezesjaren;dezejarenvertegenwoordigdeneenbredevariatieinweersfactorengedurendedekorrelvulling.Erwerdvastgestelddatookonderveldomstandighedendetemperatuurvanbepalendeinvloedisopdesnelheidenduurvandekorrelvulling.Deinvloed
vandetemperatuuropdekorrelopbrengstwordtechtergemaskeerddoordeco-variantie
tussentemperatuurenlichtintensiteitinhetveld.
Uithetverloopvandekoolhydratenaccumulatieindestengelendebenuttingvan
assimilatendoordekorrelwerdafgeleiddatdekorrelgroeigedurendedeeerstedrieweken
nadebloeimeergereguleerdwordtdoordetemperatuurdandoordebeschikbaarheidvan
assimilaten.Gedurendedetweedehelftvandekorrelvullingsperiodereageerdendekorrels
positiefingroeisnelheidopdeextraassimilatendiebeschikbaarkomenbijeenverlenging
vandefotosynthese-activiteit.Ditwijstopeensub-optimaletoevoervanassimilatenin
dezefase.ErwerdgeconcludeerddatonderNederlandsegroei-omstandighedenbijwintertarwedeopslagcapaciteitvandekorrelsbeperkendisgedurendedeeerstewekennade
bloei ('sink'-beperking),terwijlnadiendetoevoervanassimilatennaardekorrelbeperkendis('source'-beperking).Tekortenaanwater,stikstofetc.ofhetoptredenvanziektenspelenhierbijeenrol.Doorlatestikstofgiftenenbestrijdingvanziektenmetfungicidenkondelevensduurvandefotosynthetischactieveorganenverlengdwordenendaarmee
dekorrelopbrengstverhoogd.Eenlate,gedeeldestikstofgiftvergrootteechterookhet
aantalkorrelsperaar.
Deproduktiviteitvaneengewasondervariërendeuitwendigeomstandighedenhangtsterk
afvanderaseigenschappen.Derelatievebetekenisvanenkeleverschillenderaseigenschappenwerdenvastgestelddooreenvergelijkingvaneenhalf-dwerg (semi-dwarf)eneenstandaardras.Hetbleekdatdehogereharvest-index (aandeelvandekorrelindebovengrondse
massa)vandehalf-dwergtendelewerdveroorzaaktdooreengunstigereaarvormingvóórde
bloeientendeledooreenhogeregroeisnelheidvandekorrelsgedurendedeeersteweken
nadebloei.Dehalf-dwerghadeenduidelijklagerstengelgewicht;daarentegenwarenbladenkafgewichtietshogerdanbijhetstandaardras.
Tussenderassenwarenerslechtskleineverschilleninstikstofopbrengsten-verdeling,maargroteverschillenindeeiwitgehaltenvandekorrels.Heteiwitgehaltevande
korrelsbleekperrassterktereagerenopweersinvloeden;eenwarmgroeiseizoenverhoogde
heteiwitgehaltesterk,terwijlineenkoelseizoenditgehaltelaagbleef.Deharvest-indexvoorstikstofvarieerdenauwelijkstussendeseizoenenentussenderassenbijhoge,
gedeeldestikstofgiften (van0,74tot0,81).Tussendegroeiseizoenenbleekeengrotevariatietebestaantenaanzienvandehoeveelheidopgenomenstikstofnadebloei;dezehoeveelheidvarieerdevan20tot501vandestikstofopbrengstindekorrel.Inhetbijzonder
alsdegroeivandevegetatieveorganenbeperktwerd,waspostfloralestikstofopnamenodig
ombijeenhoogopbrengstniveauaandebehoeftevandekorrelstevoldoen.Eendergelijke
lateopnamevanstikstofwijstophetvrijkomenvanstikstofreservesuithetwortelsysteem
en/ofopeenlangereactiviteitvanhetwortelstelsel.
34
! f
De landbouwkundigemogelijkhedenenbeperkingenvooreenverdereverhogingvande
korrelopbrengst zijnbesproken:Erwordtgeconcludeerd,dateenverdereverbeteringvan
dekorrelopbrengst opeenevenwichtigewijzemoetwordennagestreefd,opdatdegewassen
aangepastblijvenaandebeperkingenvanhungroeimilieu.Tevenswordtopgemerktdateen
verderetoenamevandekorrelopbrengst kanwordenverwachtvaneengroteraantalkorrels
pereenheidvangrondoppervlak,vaneenlangereactiviteitvanhetwortelstelselnade
bloeienvaneenverlengdeduurvanopnameenomzettingvanassimilatendoordekorrel.
35