title: The physiological links of the increased photosystem II activity in moderately desiccated Porphyra haitanensis (Bangiales, Rhodophyta) to the cyclic electron flow during desiccation and re-hydration.
abstract: Photosynthetic electron flow changed considerably during desiccation and re-hydration of the intertidal macroalgae Porphyra haitanensis. Activities of both photosystem (PSI) and photosystem (PSII) increased significantly at moderate desiccation levels. Whereas PSII activity was abolished at an absolute water content (AWC) <24 %, PSI remained active with progressive decreases in AWC to values as low as 16 %. This result suggested that cyclic electron flow around PSI was still active after inactivation of linear electron flow following severe desiccation. Moreover, the PSI activity was restored more rapidly than that of PSII upon re-hydration. Pretreatment of the blades with 3-(3',4'-dichlorophenyl)-1,1-dimethylurea (DCMU) suppressed PSII activity following desiccation to an AWC of ~16 % AWC. Cyclic electron flow around PSI decreased markedly in blades pretreated with DCMU than in blades without pretreatment of DCMU during re-hydration in seawater containing DCMU. All results suggested that the activity of PSII under desiccation conditions plays an important role in the operation of cyclic electron flow during desiccation and its recovery during re-hydration. Therefore, we proposed the PSII activity during desiccation could eventually lead to the accumulation of NADPH, which could serve as electron donor for P700(+) and promote its recovery during re-hydration, thereby favoring the operation of cyclic electron flow.
authors.affiliation: Institute of Oceanology, Chinese Academy of Sciences (IOCAS), 7 Nanhai Road, Qingdao, 266071, People's Republic of China.
authors.forename: Shan
authors.initials: S
authors.lastname: Gao
authors.forename: Jianfeng
authors.initials: J
authors.lastname: Niu
authors.forename: Weizhou
authors.initials: W
authors.lastname: Chen
authors.forename: Guangce
authors.initials: G
authors.lastname: Wang
authors.forename: Xiujun
authors.initials: X
authors.lastname: Xie
authors.forename: Guanghua
authors.initials: G
authors.lastname: Pan
authors.forename: Wenhui
authors.initials: W
authors.lastname: Gu
authors.forename: Daling
authors.initials: D
authors.lastname: Zhu
mesh_terms: D003890:Desiccation; D004579:Electron Transport; D008954:Models, Biological; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D045331:Photosystem I Protein Complex / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D018515:Plant Leaves / Q000502:physiology; D044664:Porphyra / Q000502:physiology*; D014867:Water / Q000502:physiology*
chemical_list: D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D014867:Water
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