Photosynthetic Decline in Ginkgo Leaves during Natural Senescence

Photosynthetic pigments, biochemical activities and chloroplast ultra-structure were investigated to survey the photosynthetic characteristics of ginkgo (Ginkgo biloba L.) leaves during natural senescence. During leaf senescence, the content of total chlorophyll decreased rapidly while the content of carotenoids changed little; the content of ATP, the activity of O2 evolution of chloroplasts, the electron transport activities, the activity of photo-phosphorylation and the activity of Ca-ATPase declined; the chloroplasts had damaged in membranes and fewer grana with loose stacks of thylakoids and more and larger osmiophilic granules. With the leaf senescence, the whole structure of chloroplasts became disorganized, the thylakoid membranes became disrupted, and chloroplast was completely disintegrated finally. In conclusion, photosynthetic abilities gradually decreased as the leaves senesced.