Acceleration of plastoquinone pool reduction by alternative pathways precedes a decrease in photosynthetic CO2 assimilation in preheated barley leaves |
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Authors: | Kana Radek Kotabová Eva Prásil Ondrej |
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Institution: | Laboratory of Biophysics, Faculty of Science, PalackýUniversity, tř. Svobody 26, 771 46 Olomouc, Czech Republic; Institute of Microbiology, Academy of Sciences of the Czech Republic, Opatovickýmlýn, 379 81 Třeboň, Czech Republic; Institute of Physical Biology, University of South Bohemia, ČeskéBudějovice, Czech Republic |
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Abstract: | Heat stress causes inhibition of photosynthetic CO2 assimilation, affects light photosynthetic reactions and accelerates alternative pathways of plastoquinone pool reduction (APPR). We have studied all these heat-sensitive processes after preheating to a broad range of physiological temperatures (24–46°C) to explore a role of these alternative pathways during heat stress. Primarily, the effective quantum yield of PSII photochemistry was reduced (at 40°C). This PSII downregulation was accompanied by the stimulation of APPR and preceded reduction of photosynthetic CO2 assimilation by 2°; it occurred after preheating at 42°C because of inhibition in Rubisco (ribulose 1,5-bisphosphate carboxylase/oxygenase) activation process. Thus, we suggest that the heat-induced stimulation of APPR is not associated with the heat-induced inhibition of Calvin cycle as it was reported for other types of stresses. A possible role of APPR in the compensation of PSII downregulation is briefly discussed. |
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