外源钙对NaCl胁迫下黄瓜幼苗叶片光合特性及碳水化合物代谢的影响

Effects of exogenous calcium on photosynthetic characteristics and carbohydrate metabolism in leaves of cucumber(Cucumis sativus L.) seedlings under NaCl stress

采用营养液栽培,以盐敏感型的黄瓜品种‘津春2号’为试材,研究外源氯化钙对盐胁迫下黄瓜幼苗叶片光合色素含量、光合气体交换参数、叶绿素荧光参数及碳水化合物代谢的影响。结果表明:与对照相比,75 mmol·L-1NaCl抑制了黄瓜幼苗叶片光合色素的合成,PSⅡ遭到破坏,植株的净光合速率降低46.9%;提高了叶片蔗糖、淀粉、可溶性总糖含量及蔗糖合酶(SS)、磷酸蔗糖合酶(SPS)活性,但淀粉水解酶活性降低。与单纯盐胁迫相比,叶片喷施外源钙缓解了NaCl胁迫对幼苗光合色素合成及光合作用的抑制,净光合速率提高18.5%;植株叶片碳水化合物含量及SS、SPS活性降低,淀粉水解酶活性提高。说明外源钙可通过提高光合色素含量、调节气孔开张、维持PSⅡ活性、调节代谢相关酶活性以减少碳水化合物积累对光合作用的负反馈抑制,从而缓解NaCl胁迫对光合作用的伤害,提高植株耐盐性。

A hydroponic experiment was conducted to investigate the effects of exogenous calcium on contents of photosynthetic pigments, photosynthetic gas exchange, chlorophyll fluorescence parameters and carbohydrate metabolism in leaves of cucumber,with a salt-sensitive cucumber（ Cucumis sativus L. ） cuhivar＇ Jinchun 2＇ under salt stress. The results showed that 75 mmol. L-I NaC1 inhibitekli the synthesis of photosynthetic pigments in leaves of cucumber seedlings, and damaged the structure of PS ]/ and the net photosynthesis was reduced by 46.9%. Furthermore, salt stress induced an increase in contents of sucrose, starch and total soluble sugar and the activities of sucrose synthase （SS） and sucrose phosphate synthase （SPS） in cucumber lea＇ces. However, the amylase activity in leaves of cucumber was reduced by salt stress. Compared with cucumber seedling treated with salt stress alone, the net photosynthesis of cucumber seedlings increased by 18.5% due to exogenous calcium application,and calcium significantly alleviated the decreased photosynthetic pigments contents,photosynthesis activities and the increased carbohydrates contents as well as SS and SPS activities in salt-stressed cucumber seedlings. In contrast, exogenous calcium increased amylase activity in cucumber leaves under salt stress. These results suggested that exogenous calcium could alleviate the damage on photosynthesis induced by salt stress and enhanced salt tolerance of cucumber seedlings by increasing photosynthetic pigments, regulating the plant stomatal opening and key enzymes activities related to carbohydrate accumulation, maintaining the PS II activity and reducing the negative feedback inhibition to photosynthesis caused by carboh3;drate accumulation in leaves under stress condition.