外源亚精胺对盐胁迫下黄瓜幼苗光合作用和根叶碳水化合物积累的影响

Effects of exogenous spermidine on photosynthesis and carbohydrate accumulation in roots and leaves of cucumber(Cucumis sativus L.) seedlings under salt stress

采用营养液水培,以盐敏感黄瓜品种‘津春2号’为试材,研究外源亚精胺(Spd)对盐胁迫下黄瓜幼苗光合作用及根叶碳水化合物积累的影响。结果表明:与对照相比,50 mmol·L-1 NaCl抑制了幼苗生长和光合作用;盐胁迫提高了叶片可溶性总糖、蔗糖、淀粉含量及根系可溶性总糖和蔗糖含量,降低根系淀粉含量;盐胁迫提高了根系磷酸蔗糖合酶(SPS)、蔗糖合酶(SS)和淀粉水解酶活性及叶片SPS、SS活性,降低叶片淀粉水解酶活性。与单纯盐胁迫相比,外施Spd显著提高了幼苗生长及光合作用,降低了叶片碳水化合物含量及根系可溶性总糖、蔗糖含量,提高了根系淀粉含量,降低了叶片中SPS、SS活性和根系SPS、SS和淀粉水解酶活性,提高叶片淀粉水解酶活性。推测外源Spd可能参与了盐胁迫下气孔调控,并调节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,从而缓解了盐胁迫对光合作用的伤害,提高了植株盐胁迫耐性。

We investigated the effects of salt stress and spermidine（Spd）application to salinized nutrient solution on photosynthesis and carbohydrate accumulation in roots and leaves with a salt-sensitive cucumber（Cucumis sativus L.）cultivar Jinchun 2.The results showed that compared with control,seedlings grown in nutrient solution salinized with 50 mmol·L-1 NaCl displayed restrained growth and photosynthesis.Salt stress induced an increase on total soluble sugar,sucrose and starch levels in cucumber leaves,also the levels of sugar and sucrose in cucumber roots,but a decrease on starch level on roots.Salt stress enhanced the activities of phosphate sucrose synthase（SPS）and sucrose synthase（SS）in leaves as well as SPS,SS and amylase activities in roots,while reduced amylase activity in leaves.The growth and photosynthesis of salt-stressed cucumber seedlings were significantly improved by exogenous Spd application to salinized nutrient solution compared with salt stress.Exogenous Spd application decreased the carbohydrate accumulation in leaves and total soluble sugar,sucrose content in roots.Moreover,exogenous Spd decreased SPS and SS activity in cucumber leaves,together with SPS,SS and amylase activity in cucumber roots,and increased amylase activity in leaves.These results suggested that exogenous Spd involved in the regulation of plant stomatal opening,and reduced negative feedback inhibition to photosynthesis caused by carbohydrate accumulation in leaves by regulating activity of key enzymes on carbohydrate accumulation,then alleviated the damage on photosynthesis and enhanced salt tolerance of cucumber seedlings.