两个早熟白菜品种对秋冬低温的适应性

Adaptation of Two Precocious Cabbage Vavieties to Low Temperature in Autumn and Winter

为分析早熟白菜品种对秋冬低温的适应性,在大田自然降温条件下测定了早熟5号和863快菜两个早熟白菜品种功能叶片的光合能力和质膜稳定性。结果显示,随着气温的下降,两个早熟白菜品种的净光合速率逐渐下降,光反应活性逐渐减小,表现为PSⅡ最大光化学效率(Fv/Fm)、单位激发态面积反应中心数目(RC/CSo)、单位激发态面积用于电子传递的能量(ETo/CSo)以及叶片综合性能指数(PI)等参数均随着气温的下降而降低。零上低温下,两个白菜品种的功能叶片均具有一定的光合能力,质膜透性相对稳定,但6℃及以下低温显著抑制其PSⅡ最大光化学效率,-5℃则直接导致其冻死。两个早熟白菜品种不耐冻与其胞内结冰破坏质膜透性有关。上述结果表明,两个早熟白菜品种虽能耐受零上低温,但耐寒性较差。

To analyze the adaptation of precocious cabbage to low temperature in autumn and winter,the stability of cell membrane and photosynthetic capacity of two precocious cabbage varieties were determined under nature low temperature.The results showed that the net photosynthetic rates and light reaction activity of the two precocious cabbage varieties declined gradually with the decrease of temperature.The maximal photochemical efficiency of PSⅡ（Fv/Fm）,RC（PSⅡ reaction centre） density per excited cross section（CSo）,energy fluxes per excited cross section for electron transport（ETo/CSo） and leaf overall performance index（PI） were all declined with the decrease of temperature.The functional leaves of the two precocious cabbage varieties both had certain photosynthetic function and stable membrane permeability at low temperature above zero,but the maximal photochemical efficiency of PS Ⅱ（Fv/Fm） decreased significantly at 6℃ and lower temperature.However,two precocious cabbages were frozen to death at-5℃.The freeze intolerance of precocious cabbage might relate to the injury of cell membrane caused by intracellular freezing.The above results suggested that the two precocious cabbage varieties could survive at low temperature above zero,but had poor cold tolerance.