Ocean School, Yantai University, Yantai, 264005, PR China.
Ocean School, Yantai University, Yantai, 264005, PR China.
Plant Physiol Biochem. 2018 Nov;132:453-464. doi: 10.1016/j.plaphy.2018.09.032. Epub 2018 Sep 28.
The interaction of widely recognized causes of eelgrass decline (high seawater temperature and limited light intensity) on photosynthetic electron transport was investigated via chlorophyll fluorescence technique. High seawater temperature combined light intensity significantly increasing the relative maximum electron transport rate (rETR); at critical temperature of 30 °C, the rETR increased with the enhancement of light intensity, indicating the elevation of overall photosynthetic performance. Based on the magnitude of effect size (η), light intensity was the predominant factor affecting the performance index (PI), indicating that photosystem II (PSII) was sensitive to light intensity. Moreover, the donor side was severely damaged as evidenced by the higher decrease amplitude of fast component and its subsequent incomplete recovery. The reaction center exhibited limited flexibility due to the slight decrease amplitude in maximum photochemical quantum yield. In contrast with PSII, photosystem I (PSI) was more sensitive to high seawater temperature, based on the magnitude of η derived from the maximal decrease in slope. High seawater temperature significantly increased PSI activity, plastoquinol reoxidation capacity, and probability for electron transfer to final PSI electron acceptors. Moreover, it combined elevated light intensity significantly stimulated the activity of cyclic electron flow (CEF) around PSI. Higher activity of both PSI and CEF contributed to balancing the linear electron transport via alleviating the over-reduction of the plastoquinone pool, exhibiting flexible regulation of photosynthetic electron transport at critical temperature. Therefore, limited light intensity decreased the tolerance of eelgrass to critical temperature, which might be a factor contributing factor in the observed decline.
采用叶绿素荧光技术研究了广为人知的导致鳗草衰退的原因（海水温度高和光照强度有限）对光合作用电子传递的相互作用。海水温度升高与光照强度显著增加相对最大电子传递速率（rETR）；在 30°C 的临界温度下，rETR 随光照强度的增强而增加，表明整体光合作用性能提高。基于效应大小（η）的大小，光照强度是影响性能指数（PI）的主要因素，表明光系统 II（PSII）对光照强度敏感。此外，供体侧受到严重损伤，表现为快速组分的降低幅度更大，随后无法完全恢复。由于最大光化学量子产量的降低幅度较小，反应中心表现出有限的灵活性。与 PSII 相比，根据斜率最大降低幅度得出的 η 值，PSI 对海水温度升高更为敏感。海水温度升高显著增加 PSI 活性、质体醌还原能力和电子向最终 PSI 电子受体的转移概率。此外，它与升高的光照强度相结合，显著刺激了 PSI 周围循环电子流（CEF）的活性。PSI 和 CEF 的更高活性有助于通过减轻质体醌库的过度还原来平衡线性电子传递，从而在临界温度下展示出对光合作用电子传递的灵活调节。因此，有限的光照强度降低了鳗草对临界温度的耐受性，这可能是观察到衰退的一个因素。
