温度对黄瓜幼苗光合生理弱光耐受性的影响

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适温25 ℃/18 ℃（昼/夜）、亚适温15 ℃/9 ℃和低温9 ℃/7 ℃对弱光(75～85 μmol·m^-2·s^-1)耐受性的影响.结果表明：弱光下黄瓜叶片的SPAD、净光合速率（P_n）、气孔导度（G_s）、蒸腾速率（T_r）、水分利用效率（WUE）、实际光化学效率（Φ_PSⅡ）、光化学猝灭（q_P）等指标下降，下降程度随温度的降低而加剧，而超氧化物歧化酶（SOD）、过氧化物酶（POD）和过氧化氢酶（CAT）活性上升.逆境解除后的恢复过程中，光合和荧光参数逐渐恢复，荧光参数恢复速度快于气体交换参数.弱光下温度越低对黄瓜幼苗叶片光合机构造成的伤害越重，低温降低了叶片对弱光的耐受性.在低温、弱光处理过程中，津研2号P_n、Φ_PSⅡ、q_P等下降程度较戴多星明显，而在随后的恢复过程中其回升速度较戴多星迟缓，表明弱光下戴多星对低温的耐受性强于津研2号.

Effects of temperature regime on low-light tolerance of Cucumis sativus seedling leaves in their photosynthesis.

In a phytotron, the effects of three temperature regimes (day/night 25 ℃/18 ℃, optimal temperature; 15 ℃/9 ℃, suboptimal temperature; and 9 ℃/7 ℃, low temperature) on the low-light (75-85 μmol·m^-2·s^-1) tolerance of two Cucumis sativus cultivars (shade-susceptible Jinyan 2 and shade-tolerant Deltastar) seedling leaves in their photosynthesis were studied. The results showed that under low light, the SPAD, net photosynthesis rate (P_n), stomatal conductance (G_s), transpiration rate (T_r), water use efficiency (WUE), actual photochemical efficiency of PSⅡ in the light (Φ_PSⅡ), and photochemical quenching of chlorophyll fluorescence (q_P) of cucumber leaves decreased, with the decrement getting more with decreasing temperature, while the superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) activities were in adverse. During the recovery process after low-light stress relieved, the parameters of gas exchange and chlorophyll fluorescence of the leaves recovered gradually, and the recovery of some gas exchange parameters lagged to that of chlorophyll fluorescence parameters. Under low light, the lower the temperature, the more damage the photosynthesis apparatus suffered, and the lesser tolerance to low light the cucumber leaves had in their photosynthesis. During the low temperature and low light treatment period, the decrease of P_n, Φ_PSⅡ, and q_P was more obvious for Jinyan 2 than for Deltastar; and during the relief period, the recovery of these parameters was slower for Jinyan 2 than for Deltastar. It was indicated that Jinyan 2 had weaker tolerance to low temperature and/or low light in its photosynthesis than Deltastar.