Aerenchymaimprovesmaizedroughttolerance743

8Percentage ofroot cortical aerenchyma

642

33

Specific seminal root respiration(µmol s–1cm–1)

0.200.150.10

0.050.006005004003002001000

33

248

331

34

284

364

High RCALow RCA

Recombinant inbred lines24833134284Recombinant inbred lines

364

Figure1.Productionofrootcorticalaerenchymaofsix

genotypesat35dafterplantinginbothwell-watered(WW)andwater-stressed(WS)conditionsinthemesocosms.Datashownaremeans SEofthemean(n=4).Meanswiththesamelettersarenotsigni cantlydifferent(P 0.05).

Specific seminal root respiration (µmol s–1 g–1)

whilelines33,248,and331(lowRCAlines)averaged0.29%RCA.Inwell-wateredconditions,therewasnosig-ni cantdifferenceforRCAamongallsixlines(P 0.05).Waterstressreducedshootbiomassofthesixlinesby39%at35DAPinmesocosms(Fig.2).Underwaterstress,thethreelineswithhighRCAhad86%moreshootbiomass

864Shoot dry weight (g)

2086420

Figure3.Speci cseminalrootrespirationperlength(upper

panel)orweight(lowerpanel)ofsixgenotypesat35dafterplanting(DAP)inbothwell-watered(WW)andwater-stressed(WS)conditionsinthemesocosms.Datashownaremeans SEofthemean(n=4).Meanswiththesamelettersarenotsigni cantlydifferent(P 0.05).

3324833134284364

High RCALow RCA

Recombinant inbred lines

Figure2.Shootdryweightofsixgenotypesat35dafter

plantinginbothwell-watered(WW)andwater-stressed(WS)conditionsinthemesocosms.Datashownaremeans SEofthemean(n=4).Meanswiththesamelettersarenotsigni cantlydifferent(P 0.05).

at35DAPcomparedwiththethreelineswithlowRCA(P 0.05)(Fig.2).

Waterstressreducedspeci crootrespirationperunitofrootlengthandweightby61%and94%,respectively(Fig.3).Inwaterstress,thehighRCAlineshad53–57%lessspeci crootrespirationperunitofrootlengthandweightthanthelowRCAlines(Fig.3).Thediameterofrootsegmentsusedforrespirationmeasurementswas0.43–0.45mmunderwaterstress,withnosigni cantdifferencesamonggenotypes(datanotshown).

Waterstresssigni cantlyincreasedrootlengthdensityindeepersoillayersat35DAPinmesocosms(P 0.05)(Fig.4).Underwaterstress,thehighRCAlineshadsigni -cantlygreaterrootlengthin100–140cmsoillayersthanthelowRCAlines(Fig.4).

Rootdryweightwassigni cantlyassociatedwithshootdryweight(Fig.5),butrootdryweightwasnotsigni cantlycorrelatedwithpercentageofrootcorticalaerenchymaforthesixmaizelinesat35DAPinbothwell-wateredandwaterstressconditionsinthemesocosms.Covariateanaly-sisshowedrootdryweightwasnon-signi cantforpercent-ageofRCA(F=0.65,P=0.57)(Fig.5).

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