Abstract: This paper studied the effects of NO donor sodium nitroprusside (SNP) on the photosynthesis and active oxygen-scavenging enzyme activities of poplar leaves under drought stress.The results showed that SNP had a remarkable positive effect on leaf water content.When the SNP level was >500 μmol·L^-1 , no significant difference in leaf water content was found between SNP treatments.SNP could increase photosynthesis rate,photochemical efficiency of PSII (Fv/Fm),and ratios of Fm/Fo and Fv/Fo,but the effects decreased with the prolongation of drought stress.The SOD and POD activities of poplar leaves were higher in short time (1 h) drought stress than in longer time (3 h) one.The activity of POD was increased by SNP,while that of SOD was changed little.With increasing SNP level,the POD and SOD activities first increased and then decreased.The NO donor could retard the accumulation of active oxygen through inducing POD and SOD activities,alleviate the effects of drought stress on photosynthesis,and increase the drought-resistance of poplar.

Key words: Fagus engleriana, Seedling estalishment, Regeneration, Light conditions, Soil nutrients