title: Cyclic electron flow around photosystem I is required for adaptation to high temperature in a subtropical forest tree, Ficus concinna.
abstract: Dissipation mechanisms of excess photon energy under high-temperature stress were studied in a subtropical forest tree seedling, Ficus concinna. Net CO(2) assimilation rate decreased to 16% of the control after 20 d high-temperature stress, and thus the absorption of photon energy exceeded the energy required for CO(2) assimilation. The efficiency of excitation energy capture by open photosystem II (PSII) reaction centres (F(v)'/F(m)') at moderate irradiance, photochemical quenching (q(P)), and the quantum yield of PSII electron transport (Phi(PSII)) were significantly lower after high-temperature stress. Nevertheless, non-photochemical quenching (q(NP)) and energy-dependent quenching (q(E)) were significantly higher under such conditions. The post-irradiation transient of chlorophyll (Chl) fluorescence significantly increased after the turnoff of the actinic light (AL), and this increase was considerably higher in the 39 degrees C-grown seedlings than in the 30 degrees C-grown ones. The increased post-irradiation fluorescence points to enhanced cyclic electron transport around PSI under high growth temperature conditions, thus helping to dissipate excess photon energy non-radiatively.
authors.affiliation: School of Forestry and Biotechnology, Zhejiang Forestry University, Lin'an 311300, China.
authors.forename: Song-heng
authors.initials: SH
authors.lastname: Jin
authors.forename: Xue-qin
authors.initials: XQ
authors.lastname: Li
authors.forename: Jun-yan
authors.initials: JY
authors.lastname: Hu
authors.forename: Jun-gang
authors.initials: JG
authors.lastname: Wang
mesh_terms: D000064:Acclimatization / Q000502:physiology; D002734:Chlorophyll / Q000378:metabolism; D004579:Electron Transport; D030681:Ficus / Q000378:metabolism*; D005453:Fluorescence; D006358:Hot Temperature; D010788:Photosynthesis; D045331:Photosystem I Protein Complex / Q000378:metabolism*; D014329:Tropical Climate
chemical_list: D045331:Photosystem I Protein Complex; D002734:Chlorophyll