选用南瓜品种银辉2号为材料,以PEG模拟水分胁迫,采用砂培法研究了不同浓度外源亚精胺(Spd)对南瓜幼苗生长、活性氧代谢、抗氧化酶活性及非酶抗氧化剂和渗透调节物质含量的影响.结果表明:0.9、1.2mmol·L-1外源Spd处理,使渗透胁迫下南瓜幼苗的生物量分别增加了43.40％和36.69％,根系OF生成速率和膜脂过氧化产物MDA的积累量下降了56.33％、43.50％;0.6、0.9 mmol·L-1 Spd处理,不同程度诱导增强了根叶抗氧化酶活性,尤其以0.9 mmol·L-1 Spd处理效果最佳,根系和叶片超氧化物歧化酶(SOD)和抗坏血酸过氧化物酶(APX)活性分别为渗透胁迫下的2.00倍、1.83倍和5.47倍、2.40倍,过氧化氢酶(CAT)、过氧化物酶(POD)活性分别提高了410.89％、300.50％和276.25％、331.18％,叶片中脯氨酸(Pro)和可溶性糖含量提高了1.76倍、1.71倍,可溶性蛋白的积累量达渗透胁迫的1.49倍,维持了较高的渗透缓冲和调节能力,根系抗坏血酸(ASA)和谷胱甘肽(GSH)含量升高了2.88倍和2.41倍;渗透胁迫下0.9 mmol· L-1外源Spd处理,抑制了活性氧(ROS)的生成,减轻了由此导致的氧化损伤,抗氧化酶活性的响应和ASA-GSH循环,保护了生物膜系统的稳定,渗透调节物质的含量变化,既维持了细胞与环境的渗透平衡,又增加了光合碳同化产物和蛋白质的积累.表明0.9 rnmol· L-1外源Spd维持了渗透胁迫下南瓜幼苗碳氮代谢的正常进行,减轻了胁迫对南瓜苗期的氧化伤害.%To explore the physiological responses of different concentrations of exogenous (Spd) on pumpkin seedlings under osmotic stress,the effects of extraneous spermidine with different concentrations on ptumpkin seedlings growth,reactive oxygen metabolism,antioxidant enzyme activity and the content of non-enzymatic antioxidant and osmotic regulation substances were studied through sand culture method with pumpkin variety-Yinhui No.2 as research material and the water stress simulated by PEG.The results showed that exogenous Spd with concentration of 0.9、1.2 mmol· L-1 respectively increased the biomass of pumpkin seedlings by 43.40％ and 36.69％.The accumulation rate of root O2-and the accumulation of MDA decreased by 56.33％ and 43.50％.application of exogenous Spd with concentrations of 0.6、0.9 mmol· L-1 induced to enhance the antioxidant enzyme activity in roots and leaves in varying degrees;especially when treated by 0.9 mmol· L-1 Spd,SOD and APX activity of roots and leaves were 2 times,1.83 times and 5.47 times,2.40 times those under osmotic stress;CAT and POD activity were respectively enhanced by 410.89％ 300.50％ and 331.18％,276.25％.The Pro and soluble sugar in leaves were increased by 1.76 times and 1.71 times,and the accumulation of soluble protein reached 1.49 times those under osmotic stress,preserving higher osmotic buffering and regulating capacity.The contents of ASA and GSH in roots increased by 2.88 times and 2.41 times.Therefore,under osmotic stress,extraneous 0.9 mmol· L-1 Spd inhibited generation of ROS and alleviated the oxidative damage.Antioxidant activity response and ASA-GSH circulation protected the biological stability of membrane system.Content changes of regulating substance penetration maintained the osmotic balance of cells and the environment while increased the photosynthetic carbon assimilation and accumulation of protein,indicating that extraneous 0.9 mmol· L-1 Spd maintained the normal carbon and nitrogen metabolism of pumpkin seedlings under osmotic stress and alleviated the oxidative damage of pumpkin seedlings.
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