中文摘要：

以小麦绵农4号幼苗叶片为试材，以-0．6MPa聚乙二醇-6000（PEG-6000）处理造成渗透胁迫，研究了外源亚精胺（spa）预处理对小麦相对含水量（RWC）、H2O2含量、丙二醛（MDA）含量、电解质渗漏以及超氧化物歧化酶（SOD）、过氧化物酶（POD）、过氧化氢酶（CAT）和抗坏血酸过氧化物酶（APX）活性的影响。在渗透胁迫处理前进行2dSpa预处理，每天用含有0．02％吐温-80的0．2mmol／LSpa溶液在8d龄幼苗叶上喷施，用含有0．2mmol/L Spa的1/2浓度的Hoagland营养液浇灌根部；以含有0．02％吐温-80的蒸馏水喷叶和1／2浓度的Hoagland营养液浇灌根部作对照。随着渗透胁迫的进行，对照幼苗叶中的RWC降低，膜脂过氧化，H2O2含量和电解质渗漏增加，Spa预处理则延缓了这些变化。渗透胁迫增加了对照幼苗叶中SOD、POD和APX活性，降低了CAT活性。在整个渗透胁迫过程中，经过Spa预处理的小麦幼苗叶片的POD、CAT和APX，特别是SOD活性均高于对照。说明Spa预处理可以诱导和维持较高的抗氧化酶活性，降低H2O2浓度，减轻由渗透胁迫造成的氧化伤害，提高渗透胁迫下小麦幼苗的抗氧化能力。

英文摘要：

The effects of spermidine （Spd） pretreatment on relative water content （RWC）, H2O2 content, malonyldialdehyde （MDA） level, electrolyte leakage and activities of superoxide dismutase （SOD）, peroxidase （POD）, catalase （CAT） and ascorbate peroxidese （APX） in wheat seedlings （ Triticum aestivum L. cv. Miannong 4） were investigated under osmotic dehydration by - 0.6 MPa polyethylene glycol 6000 （ PEG-6000）. Half of eight-day-old seedlings （control） were daily sprayed with distilled water ＋ 0.02% （V/V） Tween-80 and irrigated with half-strength Hoagland＇s nutrient solution, and the other half seedlings （Spd pretreatment） were daily sprayed with 0.2 mmol/L Spd ＋ 0.02 % （ V/V） Tween-80 and irrigated with 0.2 mmol/L Spd ＋ half-strength Hoagland＇ s nutrient solution for 2 days before osmotic stress. The results showed that the RWC decreased, lipid peroxidated, as well as H2O2 content and electrolyte leakage increased in seedling leaves of control under osmotic stress, while these changes deferred in Spd pretreatment. Under osmotic stress, the activities of SOD, POD and APX increased, but CAT activity decreased in control. Spd pretreatment increased the activities of SOD and POD. Moreover, the activities of POD, CAT and APX, especially SOD in seedling leaves of Spd pretreated were higher than those of control during the throughout osmotic stress period. It suggested that Spd could induce and maintain the higher level of antioxidant enzyme activities, and decrease the concentration of H2O2, therefore alleviate oxidative damages by osmotic stress, and promote antioxidant capacity of wheat seedlings under osmotic stress.