Abstract: Under the treatment of low temperature (2°C or 5°C ) in dark for 1-2 days, the activity of both superoxide dismutase (SOD) and peroxidase (POX) in the rice seedlings of these varieties of different cold-endurance in Yunnan Plateau were decreased with varying degress. The activity of both SOD and POX in these varieties with strong cold-endurance at light (28 °C, 2500 Ix) after chilling treatment are much higher than control. But the activity in these varieties with weak cold-endurance still are lower than control. The contents of ascorbic acid (ASA) and glutathione (GSH) were decreased gradually but the content of malondialdehyde (MDA) was increased with lenghthening time exposed to chilling temperature, strengthening chill-stress and recovery at light. Decrease of contents of ASA and GSH in these varieties with strong cold-endurance is smaller and increase of content of MDA is smaller, too.

Key words: Rice seedlings. Chilling stress