Abstract: Using the Secale cereal L. (rye) as material, polyethylene glycol (PEG6000) was used to simulate drought stress, and three kinds of drought (mild, moderate and severe) with 5%（D1),10%(D2) and 15%(D3) and control group (CK) were set up, and the temperatures were 10,5,0,-5,0,5,10 ℃, we studied the effects of freezethaw and drought stress on the antioxidant enzyme activities and mass ratio of proline in seedlings. The results show that the superoxide dismutase (SOD) and peroxidase (POD) activities and mass ratio of proline of rye seedlings were increased under single drought stress. The SOD activity increased first and then decreased significantly, while the POD activity and mass ratio of proline  increased first and then decreased slowly under the combined stress. The enzyme activities and mass ratio of proline of different treatment groups reach the maximum at -5 ℃, and there is significant difference with other temperatures (P<0.05). The injured degree of seedlings caused by different stresses is combined stress>single drought stress>single freezethaw stress. The injured degree is severe drought+freeze-thaw>mild drought+freeze-thaw>single freeze-thaw>moderate drought+freeze-thaw under the combined stress treatments. The combined stress has a superimposed effect on plant damage, and a proper drought treatment can alleviate the physiological damage of freezethaw to the seedlings. Therefore, plants can alleviate the damage by improving antioxidant enzyme activity and osmotic adjustment substances under freezethaw and drought stress.

Key words: Secale cereal L., freezethaw, drought, proline, antioxidant enzyme activity