外源腐胺对根际低氧胁迫下黄瓜幼苗多胺和抗氧化系统的影响

采用营养液栽培,研究了外源腐胺(Put)对根际低氧胁迫下黄瓜幼苗体内多胺含量和抗氧化系统的影响.结果显示,低氧胁迫显著刺激了黄瓜幼苗体内活性氧(ROS)和内源多胺含量的增加,提高了抗氧化酶活性;外源Put进一步提高了低氧胁迫下黄瓜幼苗体内多胺的含量和抗氧化酶活性,降低了ROS含量,从而缓解了低氧胁迫的伤害作用;Put合成抑制剂D-精氨酸(D-Arg)不仅显著抑制黄瓜幼苗体内多胺的合成,而且抑制抗氧化酶活性,同时ROS大量积累,进一步抑制黄瓜幼苗的生长;而外源Put可缓解D-Arg的抑制作用;Put转化抑制剂甲基乙二醛-双(脒基腙)(MGBG)和Put降解抑制剂氨基胍(AG)的混合施用造成游离态Put的过量积累,以及亚精胺(Spd)、精胺(Spm)含量和抗氧化酶活性的显著降低,造成ROS大量积累,进一步加重了低氧胁迫对植株的伤害.结果表明,低氧胁迫下外源Put可提高黄瓜幼苗体内游离态Put含量,促进游离态Put向Spd和Spm转化,Spd、Spm含量的增加以及(free-Spd free-Spm)/free-Put比值的升高有利于提高植株抗氧化酶活性,增强清除ROS的能力,降低膜脂过氧化的伤害,从而增强植株的低氧胁迫耐性.

Effects of Exogenous Putrescine on Polyamines and Antioxidant System in Cucumber Seedlings under Root-zone Hypoxia Stress

The experiment was carried out to study the effects of exogenous putrescine(Put) on polyamines contents and antioxidant system in cucumber seedlings under root-zone hypoxia stress in solution culture.The results showed that root-zone hypoxia stress significantly increased the contents of reactive oxygen species(ROS) and polyamines,and antioxidant enzyme activities in seedlings.Exogenous Put application in nutrient solution furtherly increased the contents of polyamines and the activities of antioxidant enzyme,reduced ROS contents,and alleviated the injury of hypoxia stress to cucumber seedlings.D-arginine(D-Arg),which is an inhibitor of Put biosynthesis,application not only inhibited polyamines synthesis,but also decreased the activities of antioxidant enzymes in cucumber seedlings.At the same time,ROS accumulated largely,and aggravated hypoxia injury to seedlings.However,exogenous Put could lessened the damage effect of D-Arg.The mixture application of methylglyoxyl-bis(guanylhydrazone)(MGBG),which is an inhibitor of Put transform,and aminogunidine(AG),which is an inhibitor of Put degradation,resulted in accumulation of free-Put,decreased contents of free-Spd,free-Spm,and the activities of antioxidant enzymes.Therefore,ROS accumulated furtherly and aggravated hypoxia injury to seedlings.The results revealed that exogenous Put could increase endogenous free-Put content,accelerate the transformation of free-Put to Spd and Spm under root-zone hypoxia stress.The increase of Spd and Spm contents and the ratio of(free-Spd free-Spm) to free-Put contribute to enhance the activities of antioxidant enzymes,to reduce ROS levels,to restrain lipid peroxidation and finally to enhance the tolerance of cucumber seedlings to hypoxia stress.