水杨酸对高温、干旱及其复合胁迫下玉米抗氧化系统及光合能力的调控效应OA

The aim of this work was to investigate the regulatory impact of salicylic acid(SA)on the antioxidant system and photosynthetic capacity of maize(Zea mays)seedlings under high temperature,drought,and the combination of these stresses.Seedlings of the maize cultivar'Xianyu 335'at the third-leaf stage were treated with a 2.5 mmol·L-1 SA solution applied as a foliar spray.High temperature and drought stress conditions were imposed using an artificial climate chamber and polyethyleneglycol-6000,respectively.The results indicate that:1)SA augmented the activities of antioxidant enzymes,including superoxide dismutase(SOD),peroxidase(POD),and catalase(CAT),under heat stress and drought stress,and reduced the accumulation of malondialdehyde(MDA)and superoxide anions(O2·-).Under combined heat and drought stress,the positive correlations among antioxidant enzymes were enhanced in the SA treatment.Specifically,the correlation coefficients between SOD and POD activity,SOD and CAT activity,and CAT and POD activity were 0.93,0.93,and 0.99,respectively.2)SA treatment elevated the levels of soluble sugars and soluble proteins in maize leaves and roots,improved cellular water retention,and increased the overall water content in maize seedlings.3)SA treatment improved the variable fluorescence(Fv)and maximum fluorescence(Fm)while reducing initial fluorescence(F0)in maize leaves under stress,but did not significantly affect Fv/Fm.Additionally,the SA treatment increased the net photosynthetic rate(Pn),transpiration rate(Tr),stomatal conductance(Gs),and intercellular CO₂ concentration(Ci).On the 5th day after the stress treatment,the values of Pn,Tr,and Gs were 28.84%,28.43%,and 34.21%higher,respectively,in the SA treatment than in the control.4)SA mitigated the inhibitory effects of stress on maize seedling growth,enhancing dry matter accumulation and the root-shoot ratio.The results of this study show that SA enhances the cooperation among antioxidant enzymes under compound stress conditions.Treatment with SA improves the removal of harmful substances,mitigates the stress-induced inhibition of photosynthesis,increases overall dry matter accumulation in plants,and improves the root-shoot ratio in maize seedlings.