Effects of Nitrogen on Photosynthesis and Antioxidant Enzyme Activities of Maize Leaf under Drought Stress

The objective of the study was to explore the effects of nitrogen on maize photosynthesis and antioxidant enzyme activities under drought stress.The results showed that under drought stress,leaf's net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr),were decreased.Drought stress decreased the leaf's the quantum yield(φPSⅡ),photochemical quenching(qP),photosystem Ⅱ(Fv/Fm),but intercellular CO2 concentration(Ci) and were increased under drought stress;Meanwhile,the superoxide dismutase(SOD),peroxidase(POD),catalase(CAT) activities and malondialdehyde(MDA) content were increased.Under drought stress Pn,Gs,Tr,φPSⅡ,qP and antioxidant enzyme activities in 225 kg/ha treatment were the highest among three nitrogen treatments,but the MDA content and qN in 225 kg/ha treatment were the lowest.These results indicated that 225 kg/ha were the optimal nitrogen application rate under drought stress in this experiment,but deficient(0) and excessive(450 kg/ha) nitrogen application were of disadvantage to photosynthesis and antioxidant enzyme activities.