Zhang Ya-Li, Hu Yuan-Yuan, Luo Hong-Hai, Chow Wah Soon, Zhang Wang-Feng
The Key Laboratory of Oasis Eco-agriculture, Xinjiang Production and Construction Group, Shihezi University, Shihezi, 832003, PR China.
Division of Plant Science, Research School of Biology, College of Medicine, Biology and Environment, The Australian National University, Canberra, ACT 0200, Australia.
Funct Plant Biol. 2011 Jul;38(7):567-575. doi: 10.1071/FP11065.
This paper reports an experimental test of the hypothesis that cotton and soybean differing in leaf movement have distinct strategies to perform photosynthesis under drought. Cotton and soybean were exposed to two water regimes: drought stressed and well watered. Drought-stressed cotton and soybean had lower maximum CO2 assimilation rates than well-watered (control) plants. Drought reduced the light saturation point and photorespiration of both species - especially in soybean. Area-based leaf nitrogen decreased in drought-stressed soybean but increased in drought-stressed cotton. Drought decreased PSII quantum yield (ΦPSII) in soybean leaves, but increased ΦPSII in cotton leaves. Drought induced an increase in light absorbed by the PSII antennae that is dissipated thermally via ΔpH- and xanthophylls-regulated processes in soybean leaves, but a decrease in cotton leaves. Soybean leaves appeared to have greater cyclic electron flow (CEF) around PSI than cotton leaves and drought further increased CEF in soybean leaves. In contrast, CEF slightly decreased in cotton under drought. These results suggest that the difference in leaf movement between cotton and soybean leaves gives rise to different strategies to perform photosynthesis and to contrasting photoprotective mechanisms for utilisation or dissipation of excess light energy. We suggest that soybean preferentially uses light-regulated non-photochemical energy dissipation, which may have been enhanced by the higher CEF in drought-stressed leaves. In contrast, cotton appears to rely on enhanced electron transport flux for light energy utilisation under drought, for example, in enhanced nitrogen assimilation.
叶片运动方式不同的棉花和大豆在干旱条件下进行光合作用具有不同策略。棉花和大豆被置于两种水分条件下：干旱胁迫和充分浇水。与充分浇水（对照）的植株相比，干旱胁迫下的棉花和大豆最大二氧化碳同化率较低。干旱降低了两个物种的光饱和点和光呼吸——尤其是大豆。基于面积的叶片氮含量在干旱胁迫的大豆中降低，但在干旱胁迫的棉花中增加。干旱降低了大豆叶片的PSII量子产率（ΦPSII），但增加了棉花叶片的ΦPSII。干旱导致大豆叶片中PSII天线吸收的光增加，该光通过ΔpH和叶黄素调节的过程以热的形式耗散，但在棉花叶片中减少。大豆叶片似乎比棉花叶片在PSI周围具有更大的循环电子流（CEF），干旱进一步增加了大豆叶片中的CEF。相比之下，干旱条件下棉花中的CEF略有下降。这些结果表明，棉花和大豆叶片在叶片运动方面的差异导致了光合作用的不同策略以及利用或耗散光能的不同光保护机制。我们认为，大豆优先利用光调节的非光化学能量耗散，干旱胁迫叶片中较高的CEF可能增强了这种耗散。相比之下，棉花在干旱条件下似乎依赖增强的电子传输通量来利用光能，例如增强氮同化。
