Differential responses of photosystems I and II to seasonal drought in two Ficus species |
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| Institution: | 1. Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, PR China;2. University of Chinese Academy of Sciences, Beijing 100049, PR China;3. Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan 650201, PR China;4. State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources, and College of Forestry, Guangxi University, Nanning, Guangxi 530004, PR China;1. NSERC/UQAT/UQAM Industrial Chair in Sustainable Forest Management, Université du Québec en Abitibi-Témiscamingue, 445, boulevard de l''Université, Rouyn-Noranda, Québec J9X 5E4, Canada;2. Institut des sciences de la forêt tempérée, Université du Québec en Outaouais, 58, rue Principale, Ripon, Québec, J0V 1V0, Canada;1. School of Nature Conservation, Beijing Forestry University, Beijing 100083, China;2. Zhejiang Provincial Key Laboratory of Plant Evolutionary Ecology and Conservation, Taizhou University, Taizhou 318000, China;1. Cavanilles Institute of Biodiversity and Evolutionary Biology, University of Valencia, Catedrático José Beltrán, 2, Paterna, E-46980, Spain;2. Department of Biology and Geology, IES Violant de Casalduch, Avinguda Castelló s/n, Benicàssim, E-12560, Spain;1. Department of Entomology and Nematology, University of California Davis, One Shields Avenue, Davis, CA 95616-8751, USA;2. Nematology Research Unit, Department of Biology, Ghent University, K.L. Ledeganckstraat 31, 9000 Ghent, Belgium |
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| Abstract: | Hemiepiphytic Ficus species exhibit more conservative water use strategy and are more drought-tolerant compared with their non-hemiepiphytic congeners, but a difference in the response of photosystem I (PSI) and photosystem II (PSII) to drought stress has not been documented to date. The enhancement of non-photochemical quenching (NPQ) and cyclic electron flow (CEF) have been identified as important mechanisms that protect the photosystems under drought conditions. Using the hemiepiphytic Ficus tinctoria and the non-hemiepiphytic Ficus racemosa, we studied the water status and the electron fluxes through PSI and PSII under seasonal water stress. Our results clearly indicated that the decline in the leaf predawn water potential (ψpd), the maximum photosynthetic rate (Amax) and the predawn maximum quantum yield of PSII (Fv/Fm) were more pronounced in F. racemosa than in F. tinctoria at peak drought. The Fv/Fm of F. racemosa was reduced to 0.69, indicating net photoinhibition of PSII. Concomitantly, the maximal photo-oxidizable P700 (Pm) decreased significantly in F. racemosa but remained stable in F. tinctoria. The fraction of non-photochemical quenching Y(NPQ)] and the ratio of effective quantum yield of PSI to PSII Y(I)/Y(II)] increased for both Ficus species at peak drought, with a stronger increase in F. racemosa. These results indicated that the enhancement of NPQ and the activation of CEF contributed to the photoprotection of PSI and PSII for both Ficus species under seasonal drought, particularly for F. racemosa. |
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| Keywords: | Non-photochemical quenching Cyclic electron flow Osmotic potential at turgor loss point Predawn leaf water potential Seasonal drought |
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