Journal
JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY
Volume 168, Issue -, Pages 59-66Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jphotobiol.2017.01.024
Keywords
Alternative electron flow; Camellia; Energy budget; Photosynthesis; Photorespiration; Photoprotection
Categories
Funding
- Scientific and Technological Leading Talent Project of Yunnan Province [2016HA005]
- Key Lab of Yunnan Wild Plant Resource [ZYS2016002]
- Youth Innovation Promotion Association of the Chinese Academy of Sciences [2016347]
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The water-water cycle (WWC) is thought to dissipate excess excitation energy and balance the ATP/NADPH energy budget under some conditions. However, the importance of the WWC in photosynthetic regulation remains controversy. We observed that three Camellia cultivars exhibited high rates of photosynthetic electron flow under high light when photosynthesis was restricted. We thus tested the hypothesis that the WWC is a major electron sink in the three Camellia cultivars when CO2 assimilation is restricted. Light response curves indicated that the WWC was strongly increased with photorespiration and was positively correlated with extra ATP supplied from other flexible mechanisms excluding linear electron flow, implying that the WWC is an important alternative electron sink to balance ATP/NADPH energy demand for sustaining photorespiration in Camellia cultivars. Interestingly, when photosynthesis was depressed by the decreases in stomatal and mesophyll conductance, the rates of photosynthetic electron flow through photosystem II declined slightly and the rates of WWC was enhanced. Furthermore, the increased electron flow of WWC was positively correlated with the ratio of Rubisco oxygenation to carboxylation, supporting the involvement of alternative electron flow in balancing the ATP/NADPH energy budget. We propose that the WWC is a crucial electron sink to regulate ATP/NADPH energy budget and dissipate excess energy excitation in Camellia species when CO2 assimilation is restricted. (C) 2016 Published by Elsevier B.V.
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