Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan 650201, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan 650201, China.
Biochim Biophys Acta Bioenerg. 2019 Nov 1;1860(11):148073. doi: 10.1016/j.bbabio.2019.148073. Epub 2019 Aug 29.
Photosystem I (PSI) is a potential target of photoinhibition under fluctuating light. However, photosynthetic regulation under fluctuating light in field-grown plants is little known. Furthermore, it is unclear how young leaves protect PSI against fluctuating light under natural field conditions. In the present study, we examined chlorophyll fluorescence, P700 redox state and the electrochromic shift signal in the young and mature leaves of field-grown Cerasus cerasoides (Rosaceae). Within the first seconds after any increase in light intensity, young leaves showed higher proton gradient (ΔpH) across the thylakoid membranes than the mature leaves, preventing over-reduction of PSI in the young leaves. As a result, PSI was more tolerant to fluctuating light in the young leaves than in the mature leaves. Interestingly, after transition from low to high light, the activity of cyclic electron flow (CEF) in young leaves increased first to a high level and then decreased to a stable value, while this rapid stimulation of CEF was not observed in the mature leaves. Furthermore, the over-reduction of PSI significantly stimulated CEF in the young leaves but not in the mature leaves. Taken together, within the first seconds after any increase in illumination, the stimulation of CEF favors the rapid lumen acidification and optimizes the PSI redox state in the young leaves, protecting PSI against photoinhibition under fluctuating light in field-grown plants.
光系统 I（PSI）是在波动光下光抑制的潜在靶标。然而，在田间生长的植物中，波动光下的光合作用调节还知之甚少。此外，在自然田间条件下，幼叶如何保护 PSI 免受波动光的影响尚不清楚。在本研究中，我们研究了野外生长的樱桃李（蔷薇科）的幼叶和成熟叶中的叶绿素荧光、P700 氧化还原状态和电致变色位移信号。在光强增加后的最初几秒钟内，幼叶表现出比成熟叶更高的类囊体膜质子梯度（ΔpH），从而防止 PSI 在幼叶中过度还原。因此，PS 在幼叶中比在成熟叶中对波动光更耐受。有趣的是，从低光到高光的过渡后，幼叶中循环电子流（CEF）的活性首先增加到一个高水平，然后降低到一个稳定的值，而在成熟叶中没有观察到这种 CEF 的快速刺激。此外，PSI 的过度还原显著刺激了幼叶中的 CEF，但没有刺激成熟叶中的 CEF。总之，在光照增加后的最初几秒钟内，CEF 的刺激有利于快速腔酸化，并优化 PSI 氧化还原状态，从而保护 PSI 免受田间生长植物中波动光下的光抑制。
