Mitigating effects of exogenous spermidine on oxidative injury induced by waterlogging stress in the roots of maize seedlings

【Objective】In order to provide theoretical basis for the agricultural practice application of polyamines,the effects of exogenous spermidine(Spd) on the antioxidant enzyme activities and metabolite contents in maize seedling roots were studied under waterlogging stress. 【Method】Two maize cultivars, Zhengdan 958(waterlogging-sensitive)and Jundan 22(waterlogging-tolerant), were used as experiment materials. Three treatments were implemented, namely the control, waterlogging and waterlogging+Spd(1 mmol/L). After treating for six days, the antioxidant enzyme activities and metabolite contents in maize seedling roots were detected. 【Result】Under waterlogging stress, the activities of these enzymes(superoxide dismutase: SOD, peroxidase: POD, catalase: CAT, and ascorbic acid oxidase:APX), relative drought weight increase rate(RDWIR) of seedling and root vigour decreased. Relative electrolyte leakage rate(RELR), generation rate and MDA contents increased, and the effect of waterlogging on Zhendan 958(waterlogging-sensitive) was more obvious than Jundan 22(waterlogging-tolerant). However, Spd treatment markedly improved the activities of SOD,POD, CAT and APX, RDWIR and root vigour of Zhendan 958, but decreased RELR, generation rate and MDA contents of Zhendan 958. Compared to waterlogging stress, the activities of SOD,POD,CAT and APX,RDWIR and root vigour increased by 46.4%,50.0%,96.0%, 31.0%,33.5% and 73.8%, while RELR, generation rate and MDA contents decreased by 28.4%,33.6% and 19.4%,respectively. 【Conclusion 】Under waterlogging stress, the appropriate concentration of Spd could decrease generation rate and the contents of MDA via increasing the activities of antioxidant enzymes in maize seedlings roots to relieve the injury of waterlogging stress to the root plasma membrane and improve root vigour and the growth of maize seedlings.