冷锻炼对甜椒叶片光合作用及其低温光抑制的影响

以冷敏感植物甜椒 (CapsicumannuumL .)抗冷性不同的两个品种为试材 ,利用CIRAS 1光合测定系统和FMS2调制式荧光仪 ,在控温控光条件下分析比较了冷锻炼苗与未经锻炼苗的叶片光合特性、叶绿素荧光参数对温度的响应。结果表明 ,随着温度的降低 ,无论是否经过锻炼 ,低温主要通过抑制碳同化能力来影响光合作用 ,并使光能过剩 ,导致低温光抑制。提高环境CO2 浓度以增强暗反应对光能的利用 ,低温光抑制减轻。 5d的亚适温锻炼过程中甜椒叶片已发生一定程度的光抑制 ,但锻炼苗叶片能在低温下维持较高的光系统II光化学效率(ФPSII)、光化学猝灭系数 (qP)和光适应下光系统II最大光化学效率 (Fv′/Fm)值 ;冷锻炼提高了两品种低温下对光抑制的抗性 ,而且对抗冷品种的作用效果更明显

Effects of Cold-hardening on Photosynthetic Performance and Chilling-induced Photoinhibition in Sweet Pepper Leaves

Two genotypes of Capsicum annuum L. were cold-hardened at sub-optimal temperature (14℃) and an irradiance of 250 μmol m-2 s-1 for 5 d. The responses of photosynthetic characteristics and particularly the chlorophyll fluorescence parameters to low temperature in cold-hardened leaves (HL) and unhardened leaves (UHL) were investigated with a CIRAS-1 photosynthetic analyzer and a FMS2 fluorometer under controlled light intensity and temperature. Along with the decreasing temperature, the carboxylation efficiency, the photosynthetic rate of light saturation and the saturating light intensity of CO2 fixation in sweet pepper leaves decreased, irrespective of varietal difference and cold-hardening. However, the apparent quantum yield of photosynthesis was less affected by the decrease in temperature, indicating that low temperature had less influence on the process of light reaction than carbon assimilation. The enhancement of light energy utilization due to strengthened carbon dioxide fixation by elevated CO2 concentrations was able to relieve the chilling-induced photoinhibition. Nevertheless, as temperature was lowered to 8℃, the relief effects of enhancing CO2 concentration became less significant. The photochemical efficiency of photosystem II excitation energy capture by open photosystem II reaction centres (Fv′/Fm′) were lower in HL than in UHL at 25℃, suggesting that photoinhibition occurred during cold-hardening. But cold-hardened leaves temperature, implying that they faced lesser excitation energy pressure. Cold hardening enhanced the resistance to chilling-induced photoinhibition of both two cultivars. However, the effects of cold hardening were more pronounced in cold-tolerant cultivar.