外源IAA对NaHCO3胁迫下黄瓜幼苗光合特性和抗氧化系统的影响

Effects of Exogenous IAA on Photosynthetic Characteristics and Antioxidative System in Cucumis sativus Seedlings under NaHCO_3 Stress

以黄瓜‘津研四号’幼苗为试材, 采用Hoagland营养液栽培, 研究了不同浓度（0、0.01、0.1、1和10 μmol·L-1） IAA处理对50 mmol·L-1 NaHCO3胁迫下黄瓜幼苗光合特性及抗氧化系统的影响。结果表明, 碱胁迫对黄瓜幼苗的生长有抑制作用, 0.01-1 μmol·L-1外源IAA处理可显著增加黄瓜幼苗的生物量; 使叶中Na＋积累降低, K＋积累增加, 且IAA的缓解效果具有浓度效应。叶绿素a、叶绿素b和类胡萝卜素含量提高, 净光合速率（Pn）和气孔导度（Gs）增加, 以1 μmol·L-1 IAA处理的效果最好。添加1 μmol·L-1外源IAA显著提高了碱胁迫下黄瓜叶中超氧化物歧化酶（SOD）、过氧化物酶（POD）、抗坏血酸过氧化物酶（APX）、脱氢抗坏血酸还原酶（DHAR）和谷胱甘肽还原酶（GR）的活性及还原型抗坏血酸（AsA）和谷胱甘肽（GSH）的含量, 降低了碱胁迫诱导的活性氧积累和膜脂过氧化反应; 而10 μmol·L-1外源IAA处理则加剧碱胁迫对黄瓜幼苗的危害。

Cucumis sativus cv.‘Jinyan No.4＇ seedlings were cultivated in Hoagland nutrient solution to study the effects of different concentrations of IAA （0, 0.01, 0. l, l and 10 μmol·L-1） on photosynthetic characteristic and antioxidative system of C. sativus leaves under 50 mmol·L-1 NaHCO3 stress. The results showed that the growth of C. sativus was inhibited by NaHCO3 stress. Application of different concentrations （0.01-1 μmol·L-1） of IAA resulted in higher biomass in alkali-stressed C. sativus seedlings, and the effect was positively related with IAA concentration. Further analysis indicated that exogenous IAA also reduced Na＋ content, and increased K＋ content. Meanwhile, contents of Chla, Chlb and Car, Pn and Gs were significantly increased. Application of 1μmol·L-1 IAA could increase activities of some antioxidant enzymes including superoxide dismutase （SOD）, peroxidase （POD）, ascorbate peroxidase （APX）, dehydroascorbate reductase （DHAR） and glutathione reductase （GR） as well as contents of ascorbate （AsA） and glutathione （GSH） under NaHCO3 stress, resulting in significant lower reactive oxygen species （ROS） accumulation and membrane lipid peroxidation in alkali-treated C. sativus leaves. In addition, 10 μmol·L-1 IAA could aggravate alkali stress effect on cucumber seedlings.