水稻生育后期叶片早衰突变体的光合特性与叶绿体超微结构观察

以旗叶早衰的水稻突变体(psf)与其野生型对照(浙恢7954)为材料，对两者在水稻抽穗开花后旗叶衰老过程中的光合速率、叶绿素荧光和叶绿体超微结构比较分析表明，旗叶早衰突变后的每穗实粒数、结实率、千粒重和单株产量均不同程度降低，以对每穗实粒数和结实率的影响程度最明显; 在水稻灌浆期间，psf旗叶的叶绿素含量、叶绿素a/b值、净光合速率(P_n)、PSII潜在活性(F_v/F_o)和最大光化学效率(F_v/F_m)均比其野生型对照明显降低，且随着抽穗开花后天数的推移，供试材料间的差异幅度呈逐渐拉大趋势; psf叶肉细胞中的叶绿体排列、形态大小及其类囊体结构在水稻抽穗开花期基本正常，但随着叶片衰老过程的推进，psf叶肉细胞中的叶绿体相继会出现沿细胞壁周缘化、外部形态缩皱变形、嗜锇颗粒增多变大、类囊体膜系统退化、片层结构完全解体等变化。其中，叶绿体沿叶肉细胞壁排列的周缘化与外形结构的球状化表现，与叶绿体类囊体膜系统损伤和开始降解之前的净光合速率(P_n)下降有关，而由类囊体膜系统受损所带来的F_v/F_m和F_v/F_o下降过程，则相对滞后于P_n和叶绿素含量下降的起始时间。

Photosynthesis and Chloroplast Ultra-Structure Characteristics of Flag Leaves for a Premature Senescence Rice Mutant

The influences of leaf premature senescence at the filling stage on photosynthesis rate,chlorophyll fluorescence and chloroplast ultra-structure were investigated using Zhehui 7954(an excellent indica restorer line)and its leaf senescence mutant(psf).The results indicated that the psf mutant had significantly negative influence on the numbers of filling grains per panicle,seed-setting rate,1000-grain weight and yield per plant,especially on the numbers of filling grains per panicle and seed-setting rate.Compared with CK,psf also exhibited dramatically lower chlorophyll content,the ratio of chlorophyll a/b,photosynthetic rate(Pn)and chlorophyll fluorescence parameters Fv/Fo and Fv/Fm at filling stage,which were further lowered in the process of maturity.No visual changes in the ultra-structure of mesophyll cells and chloroplasts were observed for psf,showing its intact thylakoid,plastoglobuli size and shape.However,abnormal shape and stacking parallel distribution of chloroplasts,near the cell wall,the degraded grana,the plastoglobuli residue and the destroyed chloroplast membrane could be detected in psf mesophyll cells,in which the appearance of stacking and spherical chloroplasts was responsible for the dropped Pn in psf leaf prior to the degradation and disintegration of thylakoid and grana membrane,thereby caused the decrease of Fv/Fo and Fv/Fm.