【摘要】 光合作用是植物对环境变化最为敏感的生理过程。通过研究高温胁迫对樟树Cinnamomum camphora叶绿素荧光诱导动力学、气体交换速率和水分利用效率的影响,以期从光合作用的角度揭示高温对樟树的危害机制。结果表明:35和45℃高温胁迫后,樟树叶绿素荧光诱导动力学曲线O到P点的荧光强度均随胁迫增强而明显降低,同时诱导动力学参数单位反应中心吸收的光能总量、单位反应中心捕获的光能总量、单位反应中心内电子传递的量子产额、光合性能指数和单位吸收面积上天线色素能量吸收的驱动力均明显降低,其中在45℃时降至最低,与对照(25℃)相比分别降低了21.7%(P<0.01), 17.6%(P<0.01), 38.8%(P<0.01), 60.2%(P<0.01)和26.9%(P<0.01)。35和45℃高温胁迫后,单位反应中心热耗散的能量明显升高,与对照相比分别增加了13.5%(P<0.05)和78.4%(P<0.01);此外,樟树光合速率、气孔导度、蒸腾速率和水分利用效率亦均明显降低,其中最大光合速率分别降低了16.0%(P<0.05)和44.6%(P<0.01)。由此可见,高温胁迫可通过降低樟树的光能吸收、量子产量和电子传递,并促进吸收光能进行热耗散,降低光系统Ⅱ效率,进而减少同化力以降低光合速率。更多还原

【Abstract】 Photosynthesis is the most sensitive physiological process for environmental variation. To uncover any detriment of high temperature from photosynthesis on Cinnamomum camphora, the effects of high temperature stress on chlorophyll fluorescence transients, gas exchange rate, and water use efficiency in the plants treated with high temperature at 25 ℃(the control), 35 ℃ and 45 ℃, respectively, were studied, and one-way analyses of variance was performed to analyze the effects of high temperature. Results showed that fluorescence intensity from O to P point in chlorophyll fluorescence transients in C. camphora declined as temperature increased. Fluorescence transient parameters significantly decreased by 21.7%(P<0.01) in absorption flux per reaction center, 17.6%(P<0.01) in trapped energy flux per reaction center, 38.8%(P<0.01) in electron transport flux per reaction center, 60.2%(P <0.01) in performance index based on absorption, and 26.9%(P<0.01) in driving force based on absorption at 45 ℃. Compared to the control, dissipated energy flux per reaction center significantly increased by 13.5%(P<0.05) and 78.4%(P<0.01), respectively, under high temperature at 35 and 45 ℃. In addition, the photosynthetic rate, stomatal conductance, transpiration rate, and water use efficiency declined at 35 and 45 ℃. The maximum photosynthetic rate significantly reduced by16.0%(P<0.05) and 44.6%(P<0.01), respectively, at 35 and 45 ℃. Therefore, high temperature stress reduced C. camphora photosystem Ⅱ efficiency by reducing light energy absorption, quantum yield, and electron transportation as well as by increasing the absorbed light energy dissipated as heat, which resulted in an assimilatory power reduction and photosynthetic rate decline.更多还原