Department of Horticulture, Zijingang Campus, Zhejiang University, Hangzhou, Zhejiang, 310058, PR China.
Physiol Plant. 2013 May;148(1):133-45. doi: 10.1111/j.1399-3054.2012.01696.x. Epub 2012 Oct 24.
The aim of this study was to examine the role of brassinosteroids (BRs) in protecting the photosynthetic apparatus from cold-induced damage in cucumber (Cucumis sativus) plants. Recovery at both high light (HL) and low light (LL) after a cooling at 10/7°C induced irreversible inhibition of CO2 assimilation, photoinhibition at photosystem I (PSI) and inhibition of enzyme activities of Calvin cycle and ascorbate (AsA)-reduced glutathione (GSH) cycle, followed by accumulation of H2 O2 and malondialdehyde. However, cold-induced photoinhibition at PSII was fully recovered at LL but not at HL. Meanwhile, recovery at HL increased electron flux to O2 -dependent alternative pathway [Ja(O2 -dependent)]. Foliar application of 24-epibrassinolide (EBR) accelerated recovery from photoinhibition of PSII but not of PSI. EBR also significantly increased CO2 assimilation, activity of Calvin cycle enzymes and electron flux to carbon reduction [Je(PCR)], with a concomitant decrease in Ja(O2 -dependent); meanwhile EBR increased the activity of enzymes in AsA-GSH cycle and cellular redox states. However, the positive effect of EBR on plant recovery was observed only at HL, but not LL. These results indicate that BR accelerates the recovery of photosynthetic apparatus at HL by activation of enzymes in Calvin cycle and increasing the antioxidant capacity, which in turn mitigate the photooxidative stress and the inhibition of plant growth during the recovery.
本研究旨在探讨油菜素内酯（BRs）在保护黄瓜（Cucumis sativus）植株的光合器官免受低温诱导损伤中的作用。在 10/7°C 下冷却后，在高光（HL）和低光（LL）下的恢复均导致 CO2 同化不可逆抑制、光系统 I（PSI）光抑制和卡尔文循环及抗坏血酸（AsA）-还原型谷胱甘肽（GSH）循环酶活性的抑制，随后 H2O2 和丙二醛积累。然而，低温诱导的 PSII 光抑制在 LL 下完全恢复，但在 HL 下没有恢复。同时，HL 下的恢复增加了电子流到 O2 依赖的替代途径[Ja（O2 依赖）]。叶片喷施 24-表油菜素内酯（EBR）可加速 PSII 光抑制的恢复，但不能加速 PSI 光抑制的恢复。EBR 还显著增加了 CO2 同化、卡尔文循环酶的活性和电子流到碳还原[Je（PCR）]，同时 Ja（O2 依赖）减少；同时，EBR 增加了 AsA-GSH 循环中酶的活性和细胞氧化还原状态。然而，EBR 对植物恢复的积极影响仅在 HL 下观察到，而在 LL 下则没有观察到。这些结果表明，BR 通过激活卡尔文循环中的酶和增加抗氧化能力来加速 HL 下光合器官的恢复，从而减轻恢复过程中的光氧化应激和植物生长抑制。
