Response of the oxidative stress defense system to autotoxicity in alfalfa seedlings
[Objective]To investigate the effects of autotoxicity on seed germination,seedling growth and leaf cell membrane oxidative defense system of alfalfa varieties.The reactive oxygen metabolism mechanism of alfalfa seedlings in response to autotoxicity was clarified to provide a theoretical basis for the prevention and control of toxic effects.[Method]The alfalfa varieties Debao and WL298HQ were selected as the test materials.Leaves at the flow-ering stage were prepared into T1(0.025 g/mL),T2(0.125 g/mL)and T3(0.225 g/mL)extracts to simulate au-totoxicity effects.The study aimed to investigate the effect of autotoxicity on seed bioactivity and allelopathic index,as well as on seedling growth,reactive oxygen species(H2O2,OH·and O2.-),antioxidant enzymes and antioxidants in the oxidative defense system,osmotic regulatory substances.[Result]The results showed that leaf extracts inhib-ited the germination of Debao and WL298HQ alfalfa seeds at different concentrations,while T3 inhibited the seedling growth.Compared with WL298HQ,Debao exhibited obvious physiological differences in response to autotoxicity.Autotoxic substances acted on the cell membrane,inducing oxidative stress,accelerating the metabolism of reactive oxygen species(ROS),leading to the excessive accumulation of MDA,H2O2 and OH·,affecting the stability of the cell membrane.Debao responded to autotoxicity by increasing leaf protective enzyme(SOD,POD,CAT,APX,GR)activity and antioxidant system(AsA,DHA)activity under T1 treatment.However,the increase in soluble sugar,soluble protein and free proline content,coupled with autotoxicity,affected the stability of the oxidative defense sys-tem,resulting in severe oxidative damage in leaves under T3 treatment.[Conclusion]WL298HQ increased the anti-oxidants activity and the accumulation of permeable substances by activating protective mechanisms,thus maintaining the relative integrity of the cell membrane and oxidative scavenging capacity.Debao responded to autotoxicity by in-creasing the ROS production greater than the ability of antioxidant defense system,resulting in oxidative damage.
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