Effects of Drought Stress on Active Oxygen Metabolism and Contents of Osmotic Adjustment Substances in the Leaves of Apple Seedling

One-year-old potted apple(Malus domestica Borkh.CV.Red Fuji) seedlings were used to investigate active oxygen metabolism and the changes of the contents of osmotic adjustment substances in the leaves under the drought stress,and to explore the possible mechanism of adapting draught stress of the seedlings.The results indicated that with the increase of time duration and stress intensity,the generating rate of superoxide anion,the contents of H2O2 and MDA gradually increased,indicating that the drought stress results in the accumulation of active of active oxygen,and leads to the lipid peroxidation of the membrane.Most significant correlations were observed between the generating rate of supper oxygen anion and MDA content,and between the contents of H2O2 and MDA.The contents of MDA,H2O2,proline,soluble sugar,and the generating rate of super oxygen anion increased under draught stress,and decreased after rewatering.The content of soluble protein had the maximum value at the 7th day under drought stress,then decreased after rewatering.It was concluded that under moderate drought stress could protect the plasma membrane stability by increasing the activities of protective enzymes and promoting the contents of organic osmotic adjustment substances.