Root cortical aerenchyma improves the drought tolerance of m(6)

Aerenchymaimprovesmaizedroughttolerance745

8Shoot dry weight (g)

6420

0.5

1.0

1.5

2.0

25

a

Percentage ofroot cortical aerenchyma

r2= 0.423, P < 0.05

201510

cd50

33WSWW

bc

b

cd

d

77

284

364

Root dry weight (g)

Percentage ofroot cortical aerenchyma

86

24833134

Recombinant inbred lines

Figure7.Productionofrootcorticalaerenchyma(RCA)of

r2= 0.0576 (ns) 4200.5

1.01.5Root dry weight (g)

2.0

sevengenotypesinbothwell-watered(WW)andwater-stressed(WS)conditionsinthe eld.Datashownaremeans SEofthemean(n=4).Meanswiththesamelettersarenotsigni cantlydifferent(P 0.05).

Figure5.Correlationofrootdryweightandshootdryweight

(upperpanel),androotdryweightandpercentageofroot

corticalaerenchyma(lowerpanel)forsixmaizelinesat35DAPinthemesocosms.Covariateanalysisshowedrootdryweightwasnon-signi cantforpercentageofRCA(F=0.65,P=0.57).Datashownaremeansfrom4replicates.

arti ciallyinducedmutationsortransformationevents(Zhu&Lynch2004;Zhu,Kaeppler,Lynch2005a,b;Zhuetal.2006).EachRILisadistinctgenotype,andcomparisonofsixtosevenRILsallowstheanalysisofaphenotypeindistinctgenomes,therebyreducingtheriskofconfounding

0.40

effectsfrompleiotropy,epistasis,orothergeneticinterac-tions(Zhu&Lynch2004).RILsareparticularlyvaluableintheanalysisofphenotypictraitsgovernedbymultiplegenes,asisthecaseforRCAinmaize(unpublisheddata).

Weusedmesocosmsinagreenhouseandmovablerainoutsheltersinthe eldtoobtainprogressivereductionofsoilwatercontent,astypicallyoccursinseasonaldrought.Plantbiomassandyieldweresigni cantlyreducedbytheimposedstresstreatment(Figs2,12&13).Wealsofoundsigni cantlydeeperrootingintermsofrootlengthdensityandrootnumberdensityinwater-stressedcom-paredwithwell-wateredplantsofallgenotypesinthetwodifferentculturesystems(Figs4,8&9),asevidencedbysoilcoresandminirhizotronmeasurements(Figs8and9).Ourresultsareconsistentwithotherstudiesofrootingdepthincropsincludingmaizeunderwaterstress(Blum&Ritchie1984;Hoadetal.2001;Sharpetal.2004;Hoetal.2005).Deeperrootinginresponsetowaterstressenhanceswater

Volumetric soil moistur

e (m3m–3)

0.350.300.250.200.15

0.100.050.00

188191194197200203206209212215218221224227230233236239242245248251255258261264267270273276279283286290293296

Figure6.Fieldsoilvolumetricwater

contentat25and50cmdepthsinbothwell-watered(WW)andwater-stressed(WS)conditionsthroughoutthegrowingseasonin2008.Datashownaremeans SEofthemean(n=4).

Ordinal date 2008

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