中文摘要：

为了探讨多胺提高作物抗旱性的机理，在渗透胁迫下，研究小麦品种豫麦18（抗旱性较强）和扬麦9号（抗旱性较弱）幼苗叶中亚精胺（Spd）含量与三种抗氧化酶——超氧化物歧化酶（SOD）、过氧化氢酶（CAT）和抗坏血酸过氧化物酶（APX）活性的变化。结果表明：渗透胁迫2 d，扬麦9号幼苗叶片的丙二醛（MDA）的上升幅度明显高于豫麦18，豫麦18幼苗叶片Spd含量以及SOD、CAT和APX活性的上升幅度明显大于扬麦9号；外源Spd处理，明显提高了扬麦9号幼苗叶片的Spd含量以及SOD、CAT和APX活性，也明显抑制其MDA含量的上升。Spd的生物合成专一性抑制剂——甲基乙二醛-双（鸟嘌呤腙）（MGBG）预处理豫麦18，再进行渗透胁迫，则明显抑制其渗透胁迫下叶片中SOD、CAT和APX活性以及Spd含量的上升，也明显促进了MDA含量的上升。从而表明，渗透胁迫下小麦幼苗叶片的Spd可能通过促进抗氧化酶活性，从而减轻活性氧对幼苗的伤害。

英文摘要：

In this paper, to probe into the mechanism by which polyamines enhance the tolerance of crops to drought, the changes in spermidine （Spd） level and activities of three antioxidation enzymes, superoxide dismutase （SOD）, catalase （CAT） and ascorbate peroxidase （APX）, were investigated in seedling leaves of two wheat （ Triticum aestivurn L. ） cultivars, Yumai 18 （drought- tolerant） and Yangmai 9 （drought - sensitive） under osmotic stress. The results indicated： On the 2th day, after polyethylene glycol （PEG） -6,000 treatment, Malondialdehyde （MDA） level increased more significantly in leaves of Yangmai 9 than that in Yumai 18, while Yumai 18 showed a more significant increase in Spd level and activities of SOD, CAT and APX than Yangmai 9. Under osmotic stress, exogenous Spd treatment resulted in increases of Spd level and activities of SOD, CAT and APX, in concert with an inhibition of increase in MDA level in seedling leaves of Yangmai 9. Pre- treatment of Yumai 18 with methylglyoxal - bis （guanylhydrazone） （MGBG）, which is an inhibitor of Spd biosynthesis, resulted in the reduction of Spd level and activities of SOD, CAT and APX, and resulted in the increase in MDA level in seedling leaves subjected to osmotic stress. The results suggest that osmoinduced increased Spd alleviate the osmoinduced reactive oxygen injury to wheat seedlings via increases of SOD, CAT and APX activities in the leaves.