亚精胺对渗透胁迫下甜瓜幼苗膜脂过氧化和抗氧化系统的影响

为探讨多胺提高作物抗渗透胁迫的生理机制，以甜瓜品种‘齐甜2号’为材料，采用营养液法培养甜瓜幼苗，以15% PEG-6000模拟渗透胁迫，研究1 mmol·L^-1亚精胺（Spd）对不同渗透胁迫时间下甜瓜幼苗的生长、活性氧代谢、抗氧化酶活性、渗透调节物质和非酶抗氧化剂的影响。结果表明：渗透胁迫后4 d，与胁迫处理相比，1 mmol·L^-1 Spd处理使甜瓜幼苗生物量提高11.34%，根系活力提高24.20%；叶片和根系H₂O₂含量、O^₂产生速率、MDA含量和相对电解质渗透率降低，叶片中分别降低30.72%、29.99%、29.34%和14.62%，根中分别降低29.33%、25.31%、28.23%和20.34%。Spd诱导甜瓜叶片和根系中抗氧化酶活性增加，与胁迫处理相比，叶中SOD、POD、CAT和APX抗氧化酶活性分别提高25.54%、28.70%、27.72%和28.41%，根中分别提高23.35%、27.38%、25.06%和20.34%。与渗透胁迫处理相比，Spd处理在渗透胁迫后16 d甜瓜幼苗叶片脯氨酸、可溶性糖和可溶性蛋白的含量分别增加46.51%、49.72%和40.25%；渗透胁迫后16 d幼苗叶片ASA含量增加62.50%，渗透胁迫后12 d幼苗叶片GSH含量增加37.17%，ASA/DHA和GSH/GSSG分别提高74.46%、60.95%。说明在渗透胁迫下1 mmol·L^-1浓度Spd能够促进甜瓜幼苗生长，稳定生物膜系统，增强甜瓜幼苗抗氧化能力，有效缓解渗透胁迫对甜瓜幼苗伤害的作用。

Effects of spermidine on membrane lipid peroxidation and antioxidative system of melon seedling under osmotic stress

To explore the physiological mechanism of polyamine to improve the drought tolerance of melon, 15% polyethylene glycol (PEG-6000) was used to simulate osmotic stress and with ‘Qi Tian No. 2’ cultivated by nutrient solution as the experiment material. The effects of 1 mmol·L^-1spermidine (Spd) on the growth, reactive oxygen metabolism，antioxidant enzyme activity, osmotic regulating substances and non|enzymatic antioxidants of melon seedlings at different drought times were investigated. The results showed that after 4 days of osmotic stress, 1 mmol·L^-1 Spd increased the biomass of melon seedlings by 11.34% and the root activity of melon seedlings by 24.20%. The H₂O₂ content, O^₂ production rate, MDA content and electrolyte leakage of melon leaves and roots were reduced by 30.72%, 29.99%, 29.34% and 14.62% respectively in leaves, and 29.33%, 25.31%, 28.23% and 20.34%, respectively in roots. The antioxidant enzyme activities of SOD, POD, CAT and APX were increased by 25.54%, 28.70%, 27.72% and 28.41% in leaves, and increased by 23.35%, 27.38%, 25.06% and 20.34% in roots, respectively. Compared with osmotic stress treatment, the contents of proline, soluble sugar and soluble protein in leaves of melon seedlings under Spd treamtment increased by 46.51%, 49.72% and 40.25% after 16 days of osmotic stress. After 16 days of osmotic stress, the content of ASA in melon seedlings increased by 62.50%. After 12 days of osmotic stress, the content of GSH increased by 37.17%, ASA/DHA increased by 74.46%, GSH/GSSG increased by 60.95%. Therefore, under osmotic stress, 1 mmol·L^-1 Spd can promote the growth of melon seedlings, stabilize the cell membrane system, enhance the antioxidant capacity of melon seedlings, and effectively alleviated the damage of osmotic stress on melon seedlings.