Abstract: Morphological, physiological and biochemical changes in wheat seedlings (cv. Yangmai 16) under low temperature treatments (-4°C, -6°C, and -8°C) were studied by means of artificial temperature-controlled phytotron. Severer freezing-injured plants were observed in treatments with lower temperature and longer stress. The symptoms of injury were that the top of leaves became yellow and wilting (the second and third grade of freezing injury), then the whole leaves were all wilting (the fourth grade of freezing injury), and main stems and most of tillers were finally dead (the fifth grade of freezing injury). No plants showed freezing injury greater than the third grade in treatments of -4°C and -6°C for 24 h. However, the treatments of -8°C for 24 h and 48 h resulted in 16.7% and 39.6% of plant being frozen to death, respectively. The activities of superoxide dismutase (SOD), catalase (CAT), and peroxide dismutase (POD) in the second leaf from the top increased at the beginning of low temperature treatments, and with the increasing of stressSOD activity declined. The contents of malonaldehyde (MDA), proline, soluble sugar, and soluble protein were significantly increased in treatments with lower temperature and longer stress. These physiological and biochemical changes may help to alleviate the low-temperature injury to wheat plants.

Key words: Wheat, Seedling stage, Low temperature, Physiological characteristics