| A field research was conducted in Yuzhong, Gansu, to investigate the influences of different levels of moisture on protective enzyme activities, lipid peroxidation, root activity, photosynthetic rate and yield. The results showed that the activities of superoxide dismutase (SOD), catalase (CAT), and peoxidase (POD) in leaves were increased during early and middle growth stages under water stress. With the pretension and enhanced levels of drought stress, activities of SOD, CAT, and POD were decreased rapidly，while the content of malondialdehyde (MDA) in leaves became increased. After 126 days since sowing, compared to full water supply (FW), SOD, CAT and POD activities under serious water stress (SW) treatment were decreased to 61.2%, 62.5% and 76.1%, respectively, and the content of MDA was increased by 18.4%. Root activity of maize was improved under short-term water stress. With the duration of water stress continued, root activity went decreased rapidly. Synthesis of photosynthate and transportation level became decreased significantly under water stress, which led to the decreases of 100-grain weight, number per spike, harvest index and grain yield by 15.1%, 54.1%, 47.4%, respectively resulting in yield loss of 45.7%. |