Effects Of Waterlogging Stress On The Growth And Physiological Metabolism Of Different Maize Gnotypes

A pot experiment with two maize varieties DH662and XD20was conducted tostudy the morphology structure and physiological characteristics of leaves and rootand regulatory effects of exogenous spermidine on photosynthesis and physiologicalcharacteristics and yield of maize after waterlogging stress. The main results weresummarized as followes:1. The root dry weight losses of DH662was significantly higher than that of XD20under waterlogging stress.The root dry weight of DH662and XD20were decreasedsignificantly by29.7%and12.1%, while root length were of DH662and XD20weredecreased significantly by50.3%and27.0%, and root activity of DH662and XD20were decreased significantly by30.6%and8.7%as compared with CK treatmentafter8days. Root aerenchyma area of DH662and XD20were2.1and5.74times ofCK and root porosity of DH662and XD20were3.7times and89.6%as comparedwith CK treatment after6days. And the aerenchyma of DH662was not developed.The root structure of DH662was damaged and reached the verge of collapse. Butroots of XD20had developed aerenchyma and remained intact. Waterlogginginduced increases in the activity of alcohol dehydrogenase, pyruvate decarboxylaseand lactate dehydrogenase in both cultivars, but the increases in DH662were morepronounced than in XD20.2. The leaf area, leaf dry weight, SAPD value and Pn of DH662were decreasedsignificantly by1%，3.3%，5.5%and19.6%, while APX and CAT activity wereincreased significantly by16.2%and20.3%as compared with CK treatment after2days. And leaf area, leaf dry weight, SAPD value, Pn, APX and CAT activity ofDH662were decreased significantly by7.0%，25.3%，47.8%，63.0%，32.3%and13.3%as compared with CK treatment after8days. The leaf area, leaf dry weight,SAPD value and Pn of XD20were decreased by1.6%，4.7%，1.9%and16.8%, whileAPX and CAT activity were increased significantly by64.3%and49.3%ascompared with CK treatment after2days. And leaf area, leaf dry weight, SAPDvalue and Pn of XD20were decreased by5.2%，4.9%，21.1%and50.2%, while APX and CAT activity were increased by26.6%and43.7%as compared with CKtreatment after8days. The SOD activity and MDA content of DH662were increasedby10.6%and39.8%as compared with CK treatment after2days, while that ofDH662were increased by12.8%and74.8%as compared with CK treatment after8days. The SOD activity of XD20were increased by4.7%and40.2%as comparedwith CK treatment after2days and8days. And MDA content of XD20wereincreased by13.8%and32.0%as compared with CK treatment after2days and8days. The difference between varieties was significant. The result showed that thedamage effect of waterlogging stress on the leaf of DH662was more than XD20.3. The average yield of DH662and XD20was increased by12.9%and10.8%aftertopdressing exogenous spermidine. The effect of waterlogging in different growthstages on maize was different. The treatment at seedling to jointing stage showedmore influence on the two varieties. And the effect of exogenous spermidine wasbest at seedling to jointing stage. The topdressing of exogenous spermidine couldimprove the utilization efficiency of light energy in different growth stages, and Pn,Gs, Ls, Fv/Fm, ΦPSII, qP of leaves, but reduce Ci and qN. The activities of SODand CAT in DH662were increased significantly by14.5%and19.9%, while those inXD20were increased significantly by4.6%and18.2%as compared with thewaterlogging treatment. And the average activity of IDH and SDH in both the twocultivars was increased by26.1%and19.6%, while the activity of APX was notincreased significantly. The exogenous spermidine could repress the cell membraneoxidation. The average root activity in DH662and XD20was increased by12.9%and MDA content was decreased by23.9%. Therefore, the topdressing of exogenousspermidine improves the physiological functions of leaves and roots, resulting inlower yield losses caused by waterlogging, but the sensitivity of different varitiesand different growth stages to Spd was different.