黄瓜幼苗光合作用对亚适温弱光胁迫的适应性

Photosynthesis adaptation of cucumber seedlings to suboptimal temperature and low light intensity stress

为探讨黄瓜光合作用对温光逆境的适应机理,研究了弱光、亚适温、亚适温弱光胁迫处理对津优3号黄瓜幼苗光合作用的影响。结果表明,弱光、亚适温、亚适温弱光胁迫均使黄瓜幼苗的光合速率(Pn)和RuBP羧化酶活性明显降低,Pn的主要限制因素是非气孔因素,但亚适温和亚适温弱光下Pn的降低与气孔限制有一定相关性。弱光和亚适温胁迫同时出现时,温度起主要作用。10d内弱光及亚适温弱光胁迫可使黄瓜幼苗叶片的光补偿点降低。弱光和亚适温弱光处理的光下实际光化学效率(ΦPSⅡ)和初始荧光(Fo)降低,暗下光化学效率(Fv/Fm)变化不大;亚适温处理的ΦPSⅡ和Fv/Fm均降低,Fo没有明显变化。说明弱光和亚适温弱光处理没有产生明显的光抑制;亚适温胁迫诱导了黄瓜叶片PSⅡ的光抑制,但对PSⅡ反应中心的损伤不明显。

In order to determine the mechanism of photosynthesis adaptation to adverse temperature and light intensity for cucumber seedlings, the effects of low light, suboptimal temperature, suboptimal temperature and low light stress on photosynthesis of cucumber seedlings were investigated with Jinyou 3 as material. The results showed that low light, suboptimal temperature, suboptimal temperature and low light stress all led to decrease in net photosynthetic rate（Pn） and RuBP carboxylase activity remarkably. Decrease in Pn under the stress condition was mainly attributed to non-stomatal limitation, besides the treatments under suboptimal temperature, suboptimal temperature and low light intensity, which had something to do with stomatal limitation. Temperature plays a primary role when suboptimal temperature and low light intensity appear simultaneously. The light compensation point decreased during ten-day low light or suboptimal temperature and low light stress. Low light or suboptimal temperature and low light stress caused decrease in actual photochemical efficiency of PS Ⅱ（ΦPSⅡ） and initial fluorescence（Fo）, little changes in maximal photochemical efficiency of PSⅡ in darkness（Fv/Fm）. Suboptimal temperature led to decrease in ΦPSⅡ and Fv/Fm, but no significant changes in Fo. This result suggested that no photo-inhibition occurred under low light or suboptimal temperature and low light intensity stress, suboptimal temperature was likely to induce PSⅡ photo-inhibition, but no significant injury to PSⅡ reaction center occurred.