黄瓜幼苗光合及荧光特性对弱光的响应

 以不耐弱光的‘津研2号’和较耐弱光的‘戴多星’黄瓜(Cucumis sativus L.)为试材，在人工气候室内研究其光合及荧光特性对弱光（75～85 μmol·m^-2·s^-1）的响应。结果表明，弱光处理后叶片光合色素含量、总叶绿素/类胡萝卜素比值呈增加趋势，尤其是戴多星更明显；叶绿素a/b比值呈减小趋势，且戴多星的减小幅度大于津研2号；净光合速率、水分利用效率呈下降趋势，戴多星下降幅度小于津研2号；叶片最大光化学效率、光系统Ⅱ实际光化学效率、光化学反应速率、光系统非环式电子传递速率、光系统Ⅱ吸收光能用于光化学反应的比例，对弱光的响应有一定差异，弱光下戴多星均有明显增加，而津研2号的增减不规律，且幅度均较小，说明弱光下戴多星对弱光的利用能力明显强于津研2号。

Effects of Low Light on Photosynthetic and Fluorescent Characteristics of Seedlings of Cucumis sativus

he effects of low light on photosynthetic and fluorescent characteristics of seedlings in cucumis sativus (shade susceptible 'Jinyan 2' and shade tolerant 'Deltastar') were investigated in the growth chamber. After treated 20 days under the low light Intensity (75-85 μmol·m^-2·s^-1), the photosynthesis pigment contents and the ratios of chlorophylls/carotenoids Chl.(a+b)/Car.) in leaves of the two cultivars increased, and the values were higher in 'Deltastar' than in 'Jinyan 2'. While, the ratios of Chl.a/b decreased, especially in 'Deltastar'. The net photosynthesis rate (Pn) and water use efficiency (WUE) in the two cultivars decreased but the smaller reduction extents and higher values were observed in 'Deltastar'. There were some differences in effects of low light on the maximal photochemical efficiency of PSⅡ in the dark (Fv/Fm), the actual photochemical efficiency of PSⅡ in the light (ΦPSⅡ), the photochemical reaction rate (Prate), the linear whole-chain electron transport rate (J) and the partitioning proportion for photochemical reaction of light energy absorbed by PSⅡ (P) between two cultivars, which the that in 'Deltastar' increased markedly, nevertheless the ruleless changes of the that in 'Jinyan 2'. It indicated that light energy use capability in 'Deltastar' was stronger than that in 'Jinyan 2' under low light.