Effects of weak light on photosynthetic characteristics and chloroplast ultrastructure of non-heading Chinese cabbage
弱光对不结球白菜光合特性与叶绿体超微结构的影响

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.