Stimulation of chlororespiration by drought under heat and high illumination in Rosa meillandina |
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Authors: | Miriam Paredes,Marí a José Quiles |
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Affiliation: | Departamento de Biología Vegetal, Facultad de Biología, Universidad de Murcia, Campus de Espinardo, E-30100 Murcia, Spain |
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Abstract: | Rosa meillandina plants were used to study the effects of water deficit on photosynthesis and chlororespiration. Plants showed high tolerance to heat and high illumination in controlled conditions that ensured that there was no water deficit. However, when heat and high illumination were accompanied by low watering photosynthetic linear electron transport was down regulated, as indicated by the reduced photochemistry efficiency of PS II, which was associated with an increase in the non-photochemical quenching of fluorescence. In addition to the effects on the photosynthetic activity, changes were also observed in the plastidial NDH complex, PTOX and PGR5. In plants exposed to heat and high illumination without water deficit, the activities and amounts of the chlororespiration enzymes, NDH complex and PTOX, remained similar to the control and only increased in response to drought, high light and heat stress, applied together. In contrast, both the PS I activity and the amount of PGR5 polypeptide were higher in plants exposed to heat and high illumination without water deficit than in those with water deficit. The results indicated that in the conditions studied, the contribution of chlororespiration to regulating photosynthetic electron flow is not relevant when there is no water deficit, and another pathway, such as cyclic electron flow involving PGR5 polypeptide, may be more important. However, when PS II activity is inhibited by drought, chlororespiration, together with other routes of electron input to the electron transfer chain, is probably essential. |
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Keywords: | DW, dry weight F, fluorescence yield Fm, maximal fluorescence yield in the dark adapted state F0, minimal fluorescence yield in the dark adapted state Fm&prime , maximal fluorescence yield in the light adapted state Fv, variable fluorescence FW, fresh weight NDH, NADH dehydrogenase NADH-FeCNR, NADH-ferricyanide oxidoreductase Nq, non-photochemical quenching PAM, pulse amplitude modulation PPFD, photosynthetic photon flux density PS, photosystem PTOX, plastid terminal oxidase ROS, reactive oxygen species RWC, relative water content TW, turgid weight Y(II), effective PS II quantum yield |
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