| Taking maize variety Zhengdan 958 as experimental material, the effects of exogenous 5-ALA on physiological characteristics and antioxidant enzyme gene expression of maize seedlings under simulated drought stress with 15% PEG-6000 were studied.The results showed that the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), the contents of malondialdehyde (MDA), proline (Pro), and soluble sugarincreased by 132.69%, 30.69%, 30.39%, 60.34%, 497.65%, and 31.36%, respectively; the contents of chlorophyll decreased by 21.33%; the net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci), transpiration rate (Tr), the maximum photochemical efficiency (Fv/Fm), the actual photochemical efficiency (ФPSⅡ), and the photochemical quenching coefficient (qP) decreased significantly by 30.79%, 68.75%, 9.15%, 53.15%, 33.33%, 47.06%, and 26.37%, respectively, but the non\|photochemical quenching coefficient (NPQ) increased significantly by 31.82% in the leaves of maize seedlings under drought stress. Spraying 25 mg·L-1 of 5-ALA obviously relieved that damage to maize seedlings caused by drought stress, compared with PEG treatment, the activities of SOD, POD, and CAT increased by 17.63%, 17.68%, and 27.48%, respectively. The contents of Pro, soluble sugar, and chlorophyll increased by 34.97%, 19.64%, and 17.82%, respectively, the contents of MDA decreased by 22.12%, and the photosynthetic fluorescence parameters Pn, Gs, Ci, Tr, Fv/Fm, ФPSⅡ, and qP increased by 79.03%, 180%, 35.77%, 161.54%, 20.00%, 88.89%, and 26.87%, respectively, and the NPQ decreased by 15.52%. At the same time, the expressions of SOD3, POD3, and CAT1 antioxidant enzyme genes obtained by real\|time fluorescence quantitative PCR also increased by 49.31%, 34.07%, and 44.17%, respectively. In conclusion, 5-ALA can alleviate the growth of maize seedlings under drought stress and enhance the drought resistance of maize seedlings. |