Fewer studies have been conducted on changes in the photosynthetic activities of hypolithic microor-ganisms,with the majority of previous research concentrating on the microbial composition and distributional properties.The hour-by-hour daily variation characteristics of chlorophyll fluorescence parameters of three hypo-lithic cyanobacteria distributed in three different aridity levels of the Hexi Corridor were studied as experimental materials using the handy PEA plant efficiency meter over a 72-hour period.The results showed that the hypolith-ic cyanobacteria exhibited daily fluctuations in their maximum photochemical quantum yield(Fv/Fm)values,reaching a higher level at approximately 06:00 a.m.and 18:00-20:00 p.m.,with the greatest values above 0.6.The Fv/Fm values were less than 0.1 at 12:00-14:00 at higher irradiance(＞2 mW·cm2),higher temperature(＞30 ℃),and lower humidity(＜12.5％)as a result of the environmental stress.Rainfall events,which may be related to the type of stone,soil,and rainfall amount in this area,caused significantly higher values of Fv/Fm for hypolithic cyanobacteria in the North Gobi of Guazhou(GZ),with mean values fluctuating from 0.1 to 0.35,and smaller fluctuations of Fv/Fm in the Dacaotan of Jiayuguan(JYG),with mean values ranging from 0.1 to 0.19.This work exposes,to some extent,variations in photosynthetic activity of hypolithic cyanobacteria throughout a day and offers a theoretical foundation for the study of hypolithic microbial communities.
维普
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