Effects of Ca 2+ and Ca 2+ +EDTA on senescence in detached leaves of hybrid rice were studied using contents of chlorophyll and soluble protein as the physiological indexes. The results show that Ca 2+ could slow down the loss of chlorophyll and soluble protein

increase the activities of superoxide dismutase(SOD)

catalase (CAT)

ascorbic acid peroxidase (AsA POD) and glutathione reductase(GR)

and raise the contents of ascorbic acid(AsA) and glutathione(GSH)

and decrease malondialdehyde(MDA) content. The activities of AsA POD and CAT

and the contents of chlorophyll

soluble protein

AsA and GSH reduced by 1～20 mmol/L EDTA.In the meantime

the activity of SOD increased

and GR activity was less affected. External Ca 2+ could weaken the effect of EDTA

and effect of 1 mmol/L Ca 2+ was larger than that of 0 1 mmol/L Ca 2+ .