Wang Shuzhi, Li Wenfeng, Wufuer Rehemanjiang, Duo Jia, Pei Liang, Pan Xiangliang
National Engineering Technology Research Center for Desert-Oasis Ecological Construction, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, 818 South Beijing Road, Urumqi 830011, China.
Xinjiang Key Laboratory of Environmental Pollution and Bioremediation, Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Urumqi 830011, China.
Plants (Basel). 2023 Nov 29;12(23):4011. doi: 10.3390/plants12234011.
Lichens are poikilohydric organisms and an important part of the ecosystem. They show high desiccation tolerance, but the mechanism of dehydration resistance still needs to be studied. The photosynthesis recovery of the photobiont in rehydrated lichen after 11-year desiccation was investigated by simultaneously monitoring both photosystem I and II (PSI and PSII) activities. The responses of the photochemical efficiency and relative electron transport rate (rETR) of PSI and PSII, and the quantum yield of the cyclic electron flow (CEF) were measured using a Dual-PAM-100 system. PSI recovered rapidly, but PSII hardly recovered in during rehydration. The maximal photochemical efficiency of PSII (/) was generally very low and reached about just 0.4 during the rehydration. These results indicated that PSII had restored little and was largely inactivated during rehydration. The quantum yield of PSI recovered quickly to almost 0.9 within 4 h and remained constant at nearly 1 thereafter. The results showed that the activation of the CEF in the early stages of rehydration helped the rapid recovery of PSI. The quantum yield of the CEF made up a considerable fraction of the quantum yield of PSI during rehydration. A regulated excess energy dissipation mechanism and non-photochemical quenching (NPQ) also recovered. However, the small extent of the recovery of the NPQ was not enough to dissipate the excess energy during rehydration, which may be responsible for the weak activity of PSII during rehydration. The results indicated that both CEF and NPQ were essential during the rehydration of the photobiont in . The methods used in the measurements of chlorophyll fluorescence and P700 absorbance changes in this study provided a speedy and simple way to detect the physiological characteristics of the photobionts of lichen during rehydration. This work improves our understanding of the mechanism behind lichen's desiccation tolerance.
地衣是变水生物，也是生态系统的重要组成部分。它们表现出很高的耐旱性，但抗脱水机制仍有待研究。通过同时监测光系统I和II（PSI和PSII）的活性，研究了脱水11年后复水的地衣中光合生物的光合作用恢复情况。使用Dual-PAM-100系统测量了PSI和PSII的光化学效率、相对电子传递速率（rETR）以及循环电子流（CEF）的量子产率。PSI恢复迅速，但复水过程中PSII几乎没有恢复。PSII的最大光化学效率（Fv/Fm）通常很低，复水期间仅达到约0.4。这些结果表明，复水期间PSII恢复很少且大部分失活。PSI的量子产率在4小时内迅速恢复到几乎0.9，此后几乎保持不变。结果表明，复水早期CEF的激活有助于PSI的快速恢复。复水期间，CEF的量子产率占PSI量子产率的相当一部分。一种调节性的过剩能量耗散机制和非光化学猝灭（NPQ）也得以恢复。然而，NPQ恢复程度较小，不足以在复水期间耗散过剩能量，这可能是复水期间PSII活性较弱的原因。结果表明，CEF和NPQ在复水过程中对光合生物都至关重要。本研究中用于测量叶绿素荧光和P700吸光度变化的方法，为检测复水期间地衣光合生物的生理特征提供了一种快速简便的方法。这项工作增进了我们对地衣耐旱机制的理解。
