紫花苜蓿幼苗氧化应激防御系统对自毒作用的响应

Response of the oxidative stress defense system toautotoxicity in alfalfa seedlings(32160330)

摘要:

【目的】 通过研究自毒作用对紫花苜蓿品种种子萌发、幼苗生长及叶片细胞膜氧化防御系统的影响，明确紫花苜蓿幼苗响应自毒作用的活性氧代谢机理，为进一步阐明自毒物质对紫花苜蓿的抑制机理和自毒效应防控提供理论基础。【方法】 选用紫花苜蓿品种德宝和WL298HQ 为试验材料，取开花期叶片制备成T1（0. 0025 g/mL）、T2（0. 0125 g/mL）、T3（0. 0225 g/mL）浸提液模拟自毒作用，研究自毒作用对种子生物活性和化感指数的影响，以及对幼苗生长、活性氧（H₂O₂、OH. 和O₂. -）、氧化防御系统中的抗氧化酶和抗氧化剂、渗透调节物质的影响。【结果】 不同浓度的叶浸提液抑制德宝和WL298HQ 苜蓿种子萌发，T3 抑制幼苗生长。与WL298HQ 相比，德宝响应自毒作用具有明显的生理差异：1） 自毒物质作用于细胞膜上，诱发了氧化应激，加速活性氧ROS 代谢，导致了MDA、H₂O₂ 和OH·过量积累；2） 德宝在T1 下可通过提高叶片保护酶（SOD、POD、CAT、APX、GR）活性和抗氧化剂（AsA、DHA）含量来响应自毒作用。但在T3 下，可溶性糖、可溶性蛋白和游离脯氨酸升高，自毒作用影响氧化防御系统的稳定性，导致叶片出现严重的氧化损伤。【结论】 WL298HQ 通过激活保护机制增加抗氧化剂的活性，以及渗透物质的积累，进而保持细胞膜的相对完整性和氧化清除能力。德宝苜蓿在自毒作用下，ROS 的产生大于抗氧化防御系统的能力，导致氧化损伤。

Abstract:

【Objective】 To investigate the effects of autotoxicity on seed germination，seedling growth and leafcell membrane oxidative defense system of alfalfa varieties. The reactive oxygen metabolism mechanism of alfalfaseedlings in response to autotoxicity was clarified to provide a theoretical basis for the prevention and control of toxiceffects.【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 seedlinggrowth. 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 reactiveoxygen species （ROS），leading to the excessive accumulation of MDA，H₂O₂ and OH·，affecting the stability of thecell 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 maintainingthe 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.