Huang Wei, Yang Ying-Jie, Zhang Shi-Bao
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China; Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan 650201, China.
Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan 650201, China.
J Plant Physiol. 2017 Feb;209:76-83. doi: 10.1016/j.jplph.2016.11.013. Epub 2016 Dec 10.
Cyclic electron flow (CEF) around photosystem I (PSI) is essential for photosynthesis in mature leaves. However, the physiological roles of CEF in immature leaves are little known. Here, we measured the PSI and PSII activities, light response changes in PSI and PSII energy quenching for immature and mature leaves of Erythrophleum guineense grown under full sunlight. Comparing with the maximum quantum yield of PSII (F/F), the immature leaves had much lower values of the maximum photo-oxidizable P700 (P) than the mature leaves, suggesting the unsynchronized development of PSI and PSII activities. Furthermore, the immature leaves displayed significantly lower capacities for the photosynthetic electron flow through PSII (ETRII) and CEF. However, when exposed to high light, the immature leaves displayed higher levels of non-photochemical quenching (NPQ) and P700 oxidation ration [Y(ND)] than mature leaves. Under high light, the similar NPQ values were accompanied with much lower CEF activity in the immature leaves. These results suggest that, in immature leaves, CEF primarily contributes to photoprotection for PSI and PSII via acidification of thylakoid lumen. By comparison, in mature leaves, a large fraction of CEF-dependent generation of ΔpH contributes to ATP synthesis and a relative small proportion favors photoprotection via lumen acidification. These findings highlight the specific roles of CEF in photosynthetic regulation in immature and mature leaves.
围绕光系统I（PSI）的循环电子流（CEF）对于成熟叶片的光合作用至关重要。然而，CEF在未成熟叶片中的生理作用却鲜为人知。在此，我们测量了在全日照下生长的几内亚铁苏木未成熟叶片和成熟叶片的PSI和PSII活性、PSI的光响应变化以及PSII能量猝灭。与PSII的最大量子产率（F/F）相比，未成熟叶片的最大光氧化型P700（P）值远低于成熟叶片，这表明PSI和PSII活性的发育不同步。此外，未成熟叶片通过PSII的光合电子流（ETRII）和CEF的能力显著较低。然而，当暴露于高光下时，未成熟叶片的非光化学猝灭（NPQ）和P700氧化率[Y(ND)]水平高于成熟叶片。在高光下，未成熟叶片中类似的NPQ值伴随着低得多的CEF活性。这些结果表明，在未成熟叶片中，CEF主要通过类囊体腔酸化对PSI和PSII起到光保护作用。相比之下，在成熟叶片中，CEF依赖的ΔpH产生的很大一部分有助于ATP合成，相对较小的比例则通过腔酸化有利于光保护。这些发现突出了CEF在未成熟叶片和成熟叶片光合调节中的特定作用。
