氮肥后移促进受渍夏玉米根系形态恢复和提高花后光合性能

Postponed nitrogen application enhances root morphology recovery and photosynthetic characteristics of summer maize waterlogging stressed at seedling stage

江淮地区受梅雨影响,玉米苗期易发生渍害,如何通过合理运筹氮肥达到减灾效果值得研究。以夏玉米品种‘隆平206’为试验材料,研究不同氮肥运筹方式[氮肥全部基施(N1)、基肥70%+拔节肥30%(N2)、基肥50%+拔节肥50%(N3)和基肥30%+拔节肥50%+大喇叭口肥20%(N4)]对苗期受渍夏玉米根系形态和花后光合性能恢复的影响,以期为苗期受渍夏玉米合理施肥提供理论依据。结果表明,苗期渍水7 d抑制根系生长,根重、根长度、根表面积和根直径均显著降低,渍水对根系形态指标抑制效应表现为:根长度>根表面积>根直径。氮肥后移对渍水后根系生长有显著的补偿效应,氮肥后移量增加,根重、根长度和根表面积显著增加。渍水胁迫解除后18 d,N1-N4处理根长度较渍水前提高1.9~5.1倍,根表面积提高6.3~10.3倍,根直径提高0.7~1.0倍,氮肥后移对根系形态指标补偿生长效应强弱表现为:根表面积>根长度>根直径。渍水使群体叶面积系数降低9.3%~22.5%,氮肥后移可提高群体叶面积系数,较全部基施处理提高3.2%~20.7%。苗期渍水7 d显著降低灌浆期间穗位叶片的光合能力,净光合速率下降,灌浆中期和末期净光合速率分别下降16.1%和28.9%,灌浆后期光合能力下降幅度高于对照,非气孔限制是导致渍水胁迫下净光合速率下降的主要原因。渍水胁迫下,氮肥后移处理改善了穗位叶光合性能,光合能力优于氮肥前移处理。在苗期易导致渍害的地区适当减少基肥比例,后移氮素至拔节期和大喇叭口期,能够对受渍夏玉米起到较好的补偿生长效应。

Maize is one of the main summer crops in Anhui Province.However,maize production in this region is often subjectedto waterlogging stress at seedling stage.Nitrogen(N)is a key nutrient that influencing growth,yield and quality of maize,but what role it plays in relieving waterlogging stress on summer maize remains unclear.Thus field experiments werecarried out to determine the effect of N application on the recovery of root morphology and photosynthetic characteristics ofsummer maize cultivar‘Longping206’after waterlogging stress at seedling stage.Under both waterlogging and control(normalwater)conditions,four treatments of different N application rates at land preparation,jointing stage,and big flare stage(N1:10∶0∶0;N2:7∶3∶0;N3:5∶5∶0and N4:3∶5∶2)were set with a total N amount of240kg?hm–2.The resultsshowed that waterlogging stress at seedling stage significantly inhibited maize root growth.Root weight,length,surface areaand diameter significantly decreased compared with those of the control.The degree of inhibiting effect on root morphologywas in the order of total root length>root surface area>root diameter.Delayed N application had a compensation effect onroot growth after waterlogging.Eighteen days after waterlogging,total root length of N1to N4treatments increased by1.9–5.1folds that before waterlogging.Root surface area and diameter increased by6.3–10.3folds and0.7–1.0folds,respectively.Thedegree of compensation effect of delayed N application on root morphology was in the order of root surface area>total rootlength>root diameter.Waterlogging stress at seedling stage significantly decreased leaf area index(LAI)at spinning stage bya range of9.3%–22.5%.Compared with N1treatment,N2,N3and N4treatments increased LAI within3.2%–20.7%underwaterlogging treatment.Waterlogging induced a noticeable decline in Pn,respectively by16.1%and28.9%compared with thecontrol at mid grain-filling and late grain-filling stages.At late grain-filling stage,Pn decreased faster than that of control.Under waterlogging stress,non-stomatal restriction was the main factor driving the decline of photosynthetic capacity.Moreover,delayed N application improved photosynthetic capacity of ear leaf,which photosynthetic capacity was better than basalN application.In conclusion,the morphological characteristics of root and leaf along with the photosynthetic characteristics ofmaize under waterlogging responded positively to delayed N supplication.Therefore to improve the growth of maize in thestudy area(which could be affected by waterlogging at seedling stage),it was recommended to apply N at jointing andbig-flare stages.