Abstract In this study, we have compared photosynthetic regulation in tobacco leaves (Nicotiana tabacum L.) grown under high light (HL) and low light (LL) by measuring chlorophyll fluorescence, P700 redox state and electrochromic shift signals. Under high light, HL-plants had much higher linear electron flow and cyclic electron flow (CEF) around photosystem I (PSI) than LL-plants. Meanwhile, HL-plants showed significantly lower proton gradient (ΔpH) across the thylakoid membranes, owing to the increased activity of chloroplast ATP synthase. The relationships between ΔpH, non-photochemical quenching (NPQ) and PSI donor side limitation [Y(ND)] differed between HL- and LL-plants. At a given ΔpH, HL-plants displayed higher NPQ and Y(ND). Furthermore, at a given CEF, LL-plants showed higher ΔpH and Y(ND). These results indicate that HL-plants down-regulate ΔpH to increase light use efficiency by enhancing the activity of chloroplast ATP synthase. In contrast, LL-plants decrease the activity of chloroplast ATP synthase to up-regulate ΔpH and to favor photoprotection. Our findings suggest that the coordination of CEF and chloroplast ATP synthase balances light use efficiency and photoprotection at different growth light conditions.

中文翻译：

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平衡不同光照条件下生长的烟叶的光利用效率和光保护

摘要 在这项研究中，我们通过测量叶绿素荧光、P700 氧化还原状态和电致变色位移信号，比较了在高光 (HL) 和低光 (LL) 下生长的烟草叶片 (Nicotiana tabacum L.) 的光合调节。在强光下，HL 植物在光系统 I (PSI) 周围的线性电子流和循环电子流 (CEF) 比 LL 植物高得多。同时，由于叶绿体 ATP 合酶的活性增加，HL 植物在类囊体膜上显示出显着较低的质子梯度 (ΔpH)。ΔpH、非光化学淬灭 (NPQ) 和 PSI 供体侧限制 [Y(ND)] 之间的关系在 HL 和 LL 植物之间有所不同。在给定的 ΔpH 下，HL 植物表现出更高的 NPQ 和 Y(ND)。此外，在给定的 CEF 下，LL 植物表现出更高的 ΔpH 和 Y(ND)。这些结果表明 HL 植物通过增强叶绿体 ATP 合酶的活性来下调 ΔpH 以提高光利用效率。相比之下，LL 植物降低叶绿体 ATP 合酶的活性以上调 ΔpH 并有利于光保护。我们的研究结果表明，CEF 和叶绿体 ATP 合酶的协调平衡了不同生长光照条件下的光利用效率和光保护。