淹水弱光复合胁迫对夏玉米根形态结构、生理特性和产量的影响

Root Morphological,Physiological Traits and Yield of Maize Under Waterlogging and Low Light Stress

【目的】随着全球气候变化,玉米生长季气象灾害频发,阴雨寡照已成为黄淮南部地区玉米的主要非生物灾害之一。本研究通过比较2个敏感性不同玉米品种在花期淹水弱光复合胁迫的根系生长动态、结构特征和生理特性,以期探明玉米根系对花期阴雨寡照胁迫的响应特征。【方法】以郑单958和豫玉22为材料,设对照(CK)、淹水(W)、弱光(S)、淹水+弱光(WS)4个不同胁迫处理,采用盆栽试验比较不同胁迫处理下玉米根干重、长度、根表面积、根体积、节根层数的动态变化特征,探明根形态结构、根生理指标及产量对淹水、弱光及复合胁迫的响应特征。【结果】淹水、弱光及其复合胁迫下玉米根总干重、根总长度、根表面积和根体积均显著下降,3种逆境以淹水弱光复合胁迫降幅最大,其次是淹水、弱光单一胁迫,W、S、WS处理的单株根干重和根长度平均比CK降低15.21%、5.08%、21.07%和14.86%、5.52%、18.14%,根表面积和根体积则比CK平均降低9.83%、4.62%、12.72%和12.62%、6.61%、16.23%;WS处理的根干重、根长度、根表面积和根体积比W处理平均降低6.64%、3.84%、3.21%和4.12%,比S处理平均降低16.55%、13.10%、8.41%和10.32%,且WS与S处理间差异显著,与W处理之间差异不显著。淹水及复合胁迫下根通气组织发达,根气腔数量、面积、孔积率和节根层数明显增加,其中W、WS处理根单位面积上气腔数量比CK平均增加5.29和10.03倍,气腔面积较CK平均增加5.76和13.27倍,根孔积率较CK平均增加8.01和10.00倍,W和WS处理节根层数平均比CK增加1—2层,但S处理与CK无差异。淹水、弱光及复合胁迫使玉米根系生理指标和产量显著降低,尤其以复合胁迫下降幅度最大,各指标处理间变化趋势为WS<W<S<CK;逆境处理期间2个品种WS处理的根活力、根总吸收面积、活跃吸收面积和活跃吸收比CK平均降低52.82%、28.48%、36.72%和20.00%,玉米产量比CK平均下降24.52%,差异显著。随淹水、弱光时间延长,根形态和根生理指标降幅越大,而根通气组织数量、面积和孔积率则增幅越大,花期处理5—7 d是根系生长忍受淹水弱光胁迫的阈值。不同品种对淹水、弱光及复合胁迫的响应程度不同,钝感型品种(郑单958)在淹水弱光胁迫下根干重、根长度、根活力、根吸收面积等指标下降幅度小于敏感型品种(豫玉22),其中郑单958的W、WS、S处理根干重和根活力比CK平均降低13.71%、4.39%、16.28%和31.95%、9.99%、51.45%,而豫玉22降幅则分别为16.71%、5.78%、25.85%和43.83%、13.44%、51.19%,且郑单958根系适应胁迫5 d后表现出恢复性生长,而豫玉22则部分指标持续下降。2个品种在淹水弱光胁迫后根结构的变化亦表现不同,郑单958根系形成的融生型气腔规则,腔壁完整,细胞排列整齐,而豫玉22根系气腔不规则,腔壁部分断裂,部分薄壁细胞裂解;郑单958根气腔面积、数量和孔积率的增加幅度远大于豫玉22,且郑单958节根层数比豫玉22增加1—2层,表现出根系更强的逆境适应性和补偿性;郑单958产量降幅小于豫玉22,其中郑单958的W、S和WS处理比CK降低17.66%、13.30%、23.47%,而豫玉22产量比CK则分别降低20.86%、14.14%、25.53%。【结论】花期淹水、弱光胁迫严重限制根系生长发育、生理特征及产量,复合胁迫的效应远大于单一胁迫,淹水胁迫效应大于弱光胁迫;根系生长花期胁迫的阈值为5—7 d,根系通过增加节根层数、改变根结构、增加气腔数量和扩大气腔面积应对逆境胁迫,并且对逆境胁迫具有主动的自调节效应和适应性生长。

【Objective】With the global climate change,meteorological disasters occur frequently during the maize growth season.In order to explore characteristics of root response to rainy and low light stress,this study was carried out to investigate root morphology,physiological traits and yield of maize under waterlogging and low light combined stress at flowering stage.【Method】Taking two different maize varieties(Zhengdan958 and Yuyu22)as research objects,the experiment,including four treatments with contrast(CK),waterlogging(W),low light(S),and waterlogging and low light(WS)was conducted to compare dynamic changes of root dry weight,root length,root surface area,root volume,nodal root layer and to analyze the morphological,anatomical and physiological characteristics and yield under different stress.【Result】The root dry weight,root length,root surface area and root volume of maize were significantly decreased under combined stress,and these indicators were the largest reductions under waterlogging and low light stress,the second reductions under waterlogging stress and the smallest reductions under low light stress.Compared to CK,root dry weight were decreased by 15.21%,5.08%,21.07%,and root length were decreased by 14.86%,5.52%,18.14%in average under waterlogging stress,low light stress and combined stress,respectively.Root superficial area and root volume were decreased by 9.83%,4.62%,12.72%and 12.62%,6.61%,16.23%under three different stress(W,S,and WS).Compared to W and S stress,root dry weight,root length,root surface area and root volume were decreased by 6.64%,3.84%,3.21%,4.12%and 16.55%,13.10%,8.41%,10.32%under WS stress,and it was significantly different between WS and S.But there was no obviously different between WS and W.Root aerenchyma numbers,root aerenchyma areas,root porosity and crown root layers were increased significantly under waterlogging stress as well as waterlogging and low light combined stress.Compared with the contrast,root aerenchyma numbers were increased significantly by 5.29 and 10.03 times with W and WS treatment in average,respectively.Then aerenchyma areas and root porosities were increased by 5.76,13.27 times and 8.01,10.00 times under W and WS treatment,respectively.Crown root layers had more 1 to 2 layers under W and WS than that under CK,however,there was not different obviously between S and CK.Root physiological traits and yield of maize were decreasing significantly under waterlogging and low light stress.Especially there was the largest decreasing under combined stress.Compared with CK,root activities,total root absorbing area,root active absorbing area and ratio of active root absorption of maize were decreased significantly by 52.82%,28.48%,36.72%and 20.00%in average under combined stress,respectively.The change order of treatments was WS<W<S<CK.The yield of maize was significantly decreased by 24.52%under combined stress in two maize varieties.With the extension of stress days,root morphology and physiological traits were more and more decreasing under waterlogging and low light stress.But aerenchyma numbers,root aerenchyma areas,root porosity were much more increasing with extension of stress days,the longer the stress days,the greater the increasing.The threshold of root growth was 5-7 d under waterlogging and low light combined stress.It had different responses to waterlogging,low light and combined stress between two maize varieties.The decreasing degree of root dry weight,root length,root activity and root absorption area was much less in insensitive cultivars(Zhengdan 958)than in sensitive cultivars(Yuyu 22)under waterlogging and low light stress.The root dry weight and root activities were decreased by 13.71%,4.39%,16.28%and 31.95%,9.99%,51.45%in Zhengdan 958 varieties under waterlogging stress,low light stress,and combined stress,respectively,but these parameters were decreased by 16.71%,5.78%,25.85%and 43.83%,13.44%,51.19%in Yuyu22 varieties under the same stress,respectively.In addition,root growth in Zhengdan 958 showed restorative growth after 5 stress days,while it showed a continuous declination in Yuyu 22 varieties after 5 stress days.There was a different change of root anatomy with different maize varieties.Under stress arenchyma shape was regular and cell wall was integrated orderly in Zhengdan958,but aerenchyma was irregular,and cell wall was ruptured partially in Yuyu 22.In addition,aerenchyma numbers,root aerenchyma areas and root porosity were much more increasing degree in Zhengdan958 than those in Yuyu 22.Under waterlogging and combined stress,maize root layer number were increased by 1 to 2 layers in Zhengdan958 than that in Yuyu22,and it showed Zhengdan958 was much stronger adaptable and compensatory growth.Yield of Zhengdan958 was much higher than that of Yuyu22.Compared with CK,the maize yield was decreased by 17.66%,13.30%,and 23.47%of Zhengdan 958 under waterlogging stress,low light stress and combined stress,respectively;At the same time,the yield was decreased by 20.86%,14.14%,and 25.53%in Yuyu 22.With the prolongation of stress days,the decreasing in Yuyu22 was greater than in Zhengdan958.【Conclusion】The root growth and development,physiological characteristics and yield were restricted severely by the waterlogging and low light stress at flowering stage.The effect of combined stress was much larger than that of single stress,and the effect of waterlogging stress was much larger than that of low light stress.The threshold value of root growth enduring stress was 5 to 7 days at flowering stage of maize,and the maize roots had positive response and compensatory growth to abiotic stress.