Study On Chloroplast Ultrastructure And Photosynthetic Characters Of Flag Leaves From High Yield Hybrid Rice During Their Senescence

Study on Chloroplast Ultrastructure and Photosynthetic Characters of Flag Leaves from High Yield Hybrid Rice During Their SenescenceThe chloroplast ultrastructure, the activities of antioxidases, the photosynthetic characters of the hybide rice flag leaves were studied during senescence. The results showed as follews:During early stage of the full-expanded flag leaves, the photosynthetic rates of flag leaves were high and steady; the electron transport activities of thylakoid membranes were increasing; the activity of antioxidase were also increasing, except CAT,; but the contents of ATP, MDA, O2- , the membrane permeabity all showed a declining trend. The like-shuttle chloroplast was small, with tightly stacking lamellae of grana. These results indicated that photosynthetic funfion was under a gradually maturing period, withouth symptoms of senescence. Meanwhile, there was no difference in these parameters between high yeild hybrid rice "Liangyouopeijiu" and "Shanyou63".During the middle stage of the full-expanded flag leaves, the net photosynthetic rate was decreasing; The Active Photosynthetic Duration (APD) of was about 35 days for "Liangyouopeijiu", 28 days for "Liangyou63", respectively. The protein, GSH, ASA and protrine content of full-expanded flag leaves, ATP content of chloroplast were decreasing, too; The activities of POD, SOD dropped after reached maximum, the activity of CAT went on dropping; The chloroplast expanded, the chloroplast grana was contorting, loosing, some of chloroplast grana decomposited. The antioxidases of "Liangyoupeijiu" were more active than those of"Shanyou63" in this period , the net photosynthetic rate of "Liangyoupeijiu" was higher than that of "Shanyou63".During late stage of the full-expanded flag leaves, the membrane of chloroplast was destroyed, a lot of chloroplast grana decomposited, the connection of chloroplast grana wasn't tight. The resistences of leaves were getting weaker, the photosynthe-sitic rate was getting lower, almost all the chloroplast showed marked symptoms of in senescence.