Abstract: To investigate the antioxidant physiological regulatory mechanisms during the germination of naturally aged alfalfa （Medicago sativa） seeds， this experiment used ‘Zhongmu No.1’ and ‘Zhongmu No.2’ alfalfa seeds stored for 4 and 7 years， respectively， as experimental materials. After being imbibed at different stages， seed germination indices， antioxidant enzyme activities of the ascorbic acid-glutathione （AsA-GSH） cycle， and antioxidant contents were measured to analyze the changes in antioxidant indices of alfalfa seeds during storage. The main results are as follows： storage for 7 years significantly reduced the germination capacity of alfalfa seeds， specifically manifested by decreases in germination potential， germination rate， germination index， vitality index， and seedling root length with increasing storage duration. Storage duration had little effect on the initial water absorption rate of seeds but influenced the progression of the imbibition stage. As storage time increased， the lag phase during the imbibition of alfalfa seeds was prolonged. Natural ageing leads to a decline in the function of the AsA-GSH cycle during imbibition. Compared to seeds stored for 4 years， alfalfa seeds stored for 7 years exhibited significantly reduced activities of catalase （CAT）， glutathione reductase （GR）， and monodehydroascorbate reductase （MDHAR） . Ascorbic acid （AsA） and glutathione （GSH） content decreased， and oxidised glutathione （GSSG） accumulated， indicating weakened reactive oxygen species （ROS） scavenging capacity and exacerbated membrane lipid peroxidation. Seeds stored for 4 years exhibited enhanced antioxidant capacity during the mid-to-late stages of imbibition by upregulating the activity of certain antioxidant enzymes， such as peroxidase （POD） and GR， thereby partially delaying the excessive accumulation of ROS. Using the membership function method， the germination capacity of alfalfa seeds was ranked as follows： ‘Zhongmu No.1’ 4 a > ‘Zhongmu No.2’. 4 a > ‘Zhongmu No.1’ 7 a > ‘Zhongmu No.2’ 7 a. Compared to the ‘Zhongmu No.2’ seeds， under natural ageing conditions， Zhongmu No. 1 exhibited relatively stable vigor and physiological status， demonstrating stronger storage tolerance.

Key words: Alfalfa seeds, Storage years, AsA-GSH cycle, Seed vigor

摘要： 为探究自然老化紫花苜蓿（Medicago sativa）种子吸胀萌发过程中抗氧化生理调控机制，本试验以贮藏4 a和7 a的‘中苜1号’‘中苜2号’紫花苜蓿种子为试验对象，测定吸胀不同阶段种子发芽特性、抗坏血酸-谷胱甘肽（AsA-GSH）循环中抗氧化酶活性和抗氧化物含量，分析贮藏种子抗氧化各指标变化规律。结果表明：贮藏7 a会显著降低紫花苜蓿种子的发芽能力，具体表现为发芽势、发芽率、发芽指数、活力指数和幼苗根长下降。贮藏年限对种子初期吸水速率影响不大，但影响了吸胀阶段进程，随着贮藏时间的延长，紫花苜蓿种子的吸胀过程中吸水滞缓期延长。自然老化会导致种子吸胀期间AsA-GSH循环功能衰退，相较于贮藏4 a的种子，贮藏7 a的紫花苜蓿种子，吸胀过程中过氧化氢酶（Catalase，CAT）、谷胱甘肽还原酶（Glutathione reductase，GR）和单脱氢抗坏血酸还原酶（Monodehydroascorbate reductase，MDHAR）活性显著降低，抗坏血酸（Ascorbic acid，AsA）和谷胱甘肽（Glutathione，GSH）含量减少，氧化型谷胱甘肽（Oxidized glutathione，GSSG）积累，表明活性氧（Reactive oxygen species，ROS）清除能力减弱，膜脂过氧化加剧。贮藏4 a的种子在吸胀中后期通过过氧化物酶（Peroxidase，POD）和GR等活性上调，一定程度上延缓了ROS的过量积累，表现出更强的抗氧化能力。隶属函数法表明，紫花苜蓿种子萌发能力排序为：‘中苜1号’4 a>‘中苜2号’4 a>‘中苜1号’7 a>‘中苜2号’7 a，相较于‘中苜2号’种子，在自然老化过程中‘中苜1号’表现出相对稳定的活力和生理状态，具有较强的耐贮性。

关键词: 紫花苜蓿种子, 贮藏年限, AsA-GSH循环, 种子活力