Effects of drought stress on ascorbic acid contents and activities of related metabolic enzymes in apple leaves

【Objective】 The study was to investigate the changes in contents ofascorbic acid and activities of related metabolic enzymes in leaves of apple plants under the drought stress conditions and primary theory for the future study of drought-resistance.【Method】 The experiment was carried out in the 2-year-old potted apple(Malus domestica Borkh.) plants to investigate the changes of relative membrane permeability,MDA content,hydrogen peroxide content(H2O2),the levels of components of ascorbate-glutathione(ASA-GSH) cycle including ASA,dehydroascorbate(DHA),GSH,oxidized glutathione(GSSG),ascorbate peroxidase(APX),monodehydroascorbate reductase(MDHAR),dehydroascorbate reductase(DHAR) and glutathione reductase(GR) under the light drought stress,moderate drought stress,severe drought stress and rewatering conditions respectively.【Result】 Relative membrane permeability,MDA and H2O2 contents were gradually increased under the drought stress conditions,and decreased after rewatering.The contents of DHA and GSH and the activities of APX,DHAR,MDHAR and GR reached the highest point at the moderate drought stress,then decreased,except ASA,whose content increased at the light drought stress and then decreased slightly,and the GSSG whose content rose steadily.The ratios of ASA/DHA and GSH/GSSG decreased under the drought stress conditions,and increased after rewatering.【Conclusion】 The recovery ability of ASA-GSH cycle declined obviously after reaching the maximum with the increasing of drought stress.