Abstract: In order to investigate the priming effect of exogenous selenium on the antioxidant capacity of alfalfa (Medicago sativa) seedlings,standard germination tests were conducted on alfalfa seeds after primed with different concentrations (0,0.5,1.0,2.0,4.0 and 8.0 mmol·L^-1) of sodium selenite solution for 0(CK),3,6,9 and 12 h,and changes of the activities of superoxide dismutase (SOD),catalase (CAT),ascorbate peroxidase (APX),glutathione reductase (GR) and malondialdehyde (MDA) content in those seedlings were examined. The results showed that the priming effects of exogenous selenium on the antioxidant capacity of alfalfa seedlings were closely related to its concentration and priming time. Primed with a low concentration (≤ 1.0 mmol·L^-1) of selenium improved the activities of SOD,CAT,APX and GR in the seedlings,which was significantly higher than CK (P<0.05);and priming with 0.5 mmol·L^-1 exogenous selenium significantly reduced the MDA content of alfalfa seedlings. However,the activities of SOD,CAT,APX and GR were significantly lower than CK in alfalfa seedlings undergoing high concentration (≥ 4.0 mmol·L^-1) of selenium primed for 12 h (P<0.05),and their MDA content was significantly higher than CK (P<0.05). These results demonstrated that priming with exogenous selenium had a double effect on the antioxidant capacity of alfalfa seedlings. Primed with 0.5 mmol·L^-1 of exogenous selenium for 12 h,the activities of antioxidant enzymes were at the highest level in alfalfa seedlings and their MDA contents at the lowest level,this might be the best priming treatments for selenium-rich production of alfalfa.

Key words: Alfalfa, Selenium, Seed priming, Seedlings, Oxidation resistance

摘要： 为探讨外源硒引发对紫花苜蓿(Medicago sativa)幼苗抗氧化能力的影响,采用不同浓度(0,0.5,1.0,2.0,4.0和8.0 mmol·L^-1)的亚硒酸钠溶液在20℃黑暗条件下引发紫花苜蓿种子0(CK),3,6,9和12 h后进行标准发芽试验,并分析其幼苗超氧化物歧化酶(Superoxide dismutase,SOD)、过氧化氢酶(Catalase,CAT)、抗坏血酸过氧化物酶(Ascorbate peroxidase,APX)、谷胱甘肽还原酶(Glutathione reductase,GR)活性及丙二醛(Maloddialdehyde,MDA)含量的变化。结果表明:外源硒浓度和引发时间与紫花苜蓿幼苗的抗氧化能力具有密切关系;低浓度(≤ 1.0 mmol·L^-1)硒引发提高了其幼苗SOD,CAT,APX和GR的活性,均显著高于CK(P<0.05),0.5 mmol·L^-1硒引发时显著降低了其MDA含量(P<0.05);高浓度(≥ 4.0 mmol·L^-1)硒引发12 h时,其幼苗SOD,CAT,APX和GR活性均显著低于CK(P<0.05),其幼苗MDA含量则显著高于CK(P<0.05),说明外源硒引发对紫花苜蓿幼苗抗氧化能力的影响具有双重效应。硒浓度为0.5 mmol·L^-1引发12 h时,紫花苜蓿幼苗的抗氧化酶活性最高,MDA含量最低,这可能是进行紫花苜蓿富硒生产的最佳引发处理。

关键词: 紫花苜蓿, 硒, 种子引发, 幼苗, 抗氧化性能