关键词: 梨, 硒, 叶片, 衰老, 抗氧化酶, 活性氧代谢

Abstract: The effects of selenium（Se）on leaf senescence and antioxidase system in Pyrus bretschneider‘Dangshan Suli’were studied after fruit harvested. The results showed that：Spraying lower Se dosage（5 mg · L-1）delayed the decrease of water content，dry weight per unit area，chlorophyll and soluble protein content significantly，increased the activities of SOD and GSH-Px，decreased the content of H2O2， and MDA significantly in the senescing leaves，thereby deferred leaf senescence about 7.25 days；But the medium（10 mg · L-1）and higher Se dosage（20 mg · L-1）were not so effective in deferring leaf senescence，the higher the dosage，the lower the effect；However，Se inhibited POD activity. Therefore，the effect of Se on leaf senescence varied depending on its dosage，lower Se dosage may be involved in leaf-senescing regulation by enhancing the activities of SOD and GSH-Px，as a result decreases the membrane lipid peroxidation，postpones the functional period of the leaves.

Key words: pear, selenium, leaf, senescence, antioxidant enzymes, reactive oxygen metabolism