弱光对不结球白菜光合特性与叶绿体超微结构的影响

研究了不结球白菜耐弱光品种“矮王”和不耐弱光品种“绿优”经弱光处理后，光合特性和叶绿体超微结构的变化.结果表明:遮荫处理后，“矮王”的总叶绿素和叶绿素b含量大幅度上升；2个品种的净光合速率（P_n）、光补偿点（LCP）、光饱和点（(LSP）、表观量子效率（AQY）、羧化效率（CE）均呈下降趋势；除光补偿点外，“矮王”的下降幅度均小于“绿优”.叶绿素荧光参数分析表明，在弱光条件下，“绿优”的光系统Ⅱ（PSII）受到伤害，F_v/F_m、ETR、Φ_PSⅡ和q_P的下降幅度均大于耐弱光品种“矮王”.电镜超微观察结果显示:“绿优”的叶绿体内部出现裂缝和孔洞，多数基质片层断裂，基粒片层解体，线粒体出现内含物减少、发生空洞的现象；而“矮王”的叶绿体结构良好，线粒体发育正常.表明弱光处理可以影响植物的光合机构，但对不同品种的影响不同.

Effects of weak light on photosynthetic characteristics and chloroplast ultrastructure of non-heading Chinese cabbage

The study with two varieties of non-heading Chinese cabbage shade-tolerant 'Aiwang' and shade-sensitive 'Lüyou' showed that after shading, the total chlorophyll and chlorophyll b contents of 'Aiwang' went up greatly, but the net photosynthetic rate (Pn) , light compensation point (LCP), light saturation point (LSP), apparent quantum yield (AQY) and carboxylation efficiency (CE) of both 'Aiwang' and 'Liiyou' all went down, and the decline of all test parameters except LCP was slighter for 'Aiwang' than for ' Lüyou'. Under weak light condition, the PS II of 'Lüyou' was injured, and as a result, the Fv/Fm, ETR, Phi PS II, and qp of 'Lüyou' had a greater decline than those of 'Aiwang'. In the chioroplast of 'Ltiyou' , cracks and foveolae appeared, most of stroma lamellae fractured, grana lamellae disaggregated, and mitochondria were nearly empty with the decrease of contents. In contrast, the chioroplast structure of 'Aiwang' was flawless, and its mitochondria grew well. It was suggested that weak light could damage the photosynthetic organization of plant, but different varieties showed different responses.