Responses of Antioxidant System in Leaves of Rhododendron jinggangshanicum to High Temperature Stress

In order to illuminate the responsive mechanism of Rhododendron jinggangshanicum Tam under high temperature stress,four-year-old seedlings of R.jinggangshanicum were planted in artificial climate chamber and the morphological,biophysical and biochemical changes of them were determined under different degree of high temperature.The results showed that:(1) After six-days' treatment at 30℃ and 38℃,the activities of peroxidase(POD),ascorbate peroxidase(APX) and catalase(CAT) in the leaves increased by 44.44% and 127.16%,33.12% and 129.35%,106.52% and 188.64% respectively,and the changes were extremely significant(P0.01).Whereas the changes of SOD were not larger,with the proportion of 3.77% and 5.11% increase,respectively.(2)With the temperature becoming higher,the contents of soluble protein and proline were increased obviously,whereas the content of ascorbic acid(AsA) was largely reduced.When we compared the content of soluble protein with the control level,all treatments reached extremely significant difference(P0.01) except for the one taking place at 30℃,which showed significant difference(P0.05).(3)With high-temperature strengthening,the content of hydrogen peroxide(H2O2) and malondialdehyde(MDA) accumulated greatly,with each treatment reaching extremely significant or significant differences.It displayed the phenomenon of plants slightly wilting,old leaves browning off and new leaves necrosis occurring.The results gave conclusions that the oxidative damage which R.jinggangshanicum suffered under the high temperature stress may be related to the obvious increase in the content of H2O2 and MDA,as well as largely reduced content of AsA.However,the plant can improve its antioxidant ability and decrease the oxidative damage caused by the high temperature stress through increasing the activities of antioxidant enzymes and the content of proline.