文档介绍：Activation of Photosynthesis and Resistance to
Photoinhibition in Cyanobacteria within
Biological Desert Crust1[w]
Yariv Harel, Itzhak Ohad, and Aaron Kaplan*
Department of Plant and Environmental Sciences (., .), Minerva Arid Ecosystems Research Center
(., .), Department of Biological Chemistry (.), and Minerva, Avron-Evenari Center of Photosynthesis
Research (., .), The Hebrew University of Jerusalem, Jerusalem, 91014, Israel
Filamentous cyanobacteria are the main primary producers in biological desert sand crusts. The cells are exposed to extreme
environmental conditions including temperature, light, and diurnal ation/rehydration cycles. We have studied the
ics of activation of photosynthesis during rehydration of the cyanobacteria, primarily Microcoleus sp., within crust samples
collected in the Negev desert, Israel. We also investigated their susceptibility to photoinhibition. Activation of the
photosynthetic apparatus, measured by fluorescence ics, thermoluminescence, and low temperature fluorescence
emission spectra, did not require de novo protein synthesis. Over 50% of the photosystem II (PSII) activity, assembled
phycobilisomes, and photosystem I (PSI) antennae were detected within less than 5 min of rehydration. Energy transfer to PSII
and PSI by the respective antennae was fully established within 10 to 20 min of rehydration. The act