Study On Photosynthetic Characters And Key Enzymes Of Photosynthsis On Flag Leaves From High Yield Hybrid Rice During Their Senescence

Activities of the hybrid rice flag leaves were studied during senescence. The results showed as follews:Throug measuring the content of chlorophyll and soluble protein in hybrid rice's flag leave,the results indicate that after ten days of full-expanded,the flag leave enter the stage of senescence.Some physiologic index: the photosynthetic rates ,the chlorophyll content, the electron transfer activities of PSI,PSII and whole chain, the activities of Ca²⁺-ATPase and Mg²⁺-ATPase,the activitie of RuBPCase also indicate activity of photosynthesis were gradually roll off after ten days of full-expanded flag leaves.So we can find the inflection point that from flag leaves senescence proceeding to senescence proceeding is at ten days after full-expanded.At all stage of flag leaves senescence, we can find the activity of C₄ pathway enzymes:PEPCase,PPDK,NADP-ME,NADP-MDH.We surmise that there are C₄ path-way in hybrid rices.Compared with RuBPCase,the max activity of C₄ pathway enzymes were later than RuBPCase and appeard in middle of senescence proceeding when the activity of RuBPCase dropped.these indicate that C₄ pathway enzymes play assistance role of RuBPCase,and supplet the hybrid rice in photosynthesis yield during middle and anaphase of senescence.The activities of antioxidases during flag senescence showed that activity of SOD was gradually decreasing but the activities of POD and CAT were increasing. Maybe POD and CAT play more important role in rice senescence.Compared with "9311" and " Aipei64S ", We also find that high yield hybrid rice "Liangyoupeijiu" has dominance in photosynthetic indix and activity of C4 path-way enzymes.In the anaphase of senescence, " Liangyoupeijiu " has lower content of MDA and higher activity of antioxidases.Through compared with "9311" and "Aipei64S" ,we surmise that higher activity of RuBPCase,C4 path-way enzymes and electron transfer chain maybe the reason that "Liangyoupeijiu" has heavy yield.