Cyclic electron flow around photosystem I is required for adaptation to high temperature in a subtropical forest tree, Ficus concinn

• Published in: Journal of Zhejiang University. B. Science no. 10; pp. 784 - 790
• Main Author: Song-heng JIN Xue-qin LI Jun-yan HU Jun-gang WANG
• Format: Journal Article
• Language: English
• Published: 2009
• Subjects: CO2同化; 亚热带; 光化学猝灭系数; 光系统I; 循环电子传递; 林木种苗; 电子流; 高温胁迫
• ISSN: 1673-1581; 1862-1783

Dissipation mechanisms of excess photon energy under high-temperature stress were studied in a subtropical forest tree seedling, Ficus concinna. Net CO2 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 CO2 assimilation. The efficiency of excitation energy capture by open photosystem Ⅱ（PSⅡ） reaction centres （Fv＇/Fm＇） at moderate irradiance, photochemical quenching （qp）, and the quantum yield of PSII electron transport （φPSⅡ） were significantly lower after high-temperature stress. Nevertheless, non-photochemical quenching （qNP） and energy-dependent quenching （qE） 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 ℃-grown seedlings than in the 30 ~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.