Studies on the Adaptive Mechanism of Rice Seedlings under the Cross Stress of Drought and High Temperature

The mechanism of adaptability to the cross stress of drought and high temperature of rice was studied by comparing the changes of the contents of osmotic regulation substances and the active oxygen removal system of rice seedlings under the stress of drought or high temperature and the cross stress of them in water culture. The results showed that the soluable sugar content,proline content,relative conductivity,O-2.production rate and H2O2 content were significantly increased while the activity of protective enzymes( SOD,POD and CAT) and the contents of GSH and ASA were significantly decreased after the treatment of high temperature or drought. The treatments with cross stress of drought and high temperature showed higher contents of soluble sugar,proline,GSH and ASA and activity of protect enzymes but lower relative conductivity,O-2.production rate and H2O2 content than those with only stress of drought or high temperature,indicating the pretreatment of a stress would improve rice seedlings in the resistance to another stress through promoting the accumulation of osmotic regulation substances and enhancing the capacity of scavenging active oxygen in rice leaf.