紫花苜蓿种子萌发对钴胁迫的生理生化响应

以"甘农3号"紫花苜蓿为试验材料,研究不同浓度Co2+(0,0.25,0.50,1.00,2.50,5.00mmol/L CoCl2)胁迫对紫花苜蓿种子萌发及幼苗生理生化特性的影响。结果表明:Co胁迫对紫花苜蓿种子的萌发及幼苗的生长有明显的抑制作用,随着Co胁迫浓度的增大,种子发芽势、发芽率、发芽指数、活力指数及幼苗的胚芽长、胚根长、根系活力和干重均显著降低,而且Co胁迫对发芽势的抑制作用大于发芽率,对胚根生长的抑制作用大于胚芽;低浓度Co胁迫(0.25和0.50mmol/L)下,苜蓿幼苗叶片中可溶性蛋白、可溶性糖含量和蛋白水解酶、超氧化物歧化酶(SOD)、抗坏血酸过氧化物酶(APX)、愈创木酚过氧化物酶(GPX)、过氧化氢酶(CAT)活性与CK均无显著差异,而游离脯氨酸含量显著升高;随着Co胁迫浓度的升高,可溶性蛋白、可溶性糖、游离脯氨酸含量及蛋白水解酶、SOD、APX、GPX、CAT活性均显著下降,超氧阴离子自由基(O2·-)产生速率、羟自由基(OH·)浓度、H2O2及丙二醛(MDA)含量均显著增加。说明高浓度Co胁迫使得苜蓿幼苗抗氧化系统活性下降,活性氧清除能力降低,膜脂过氧化程度加剧,从而抑制了紫花苜蓿种子的萌发及幼苗的生长。

Physiological and biochemical responses of Medicago sativa seed to cobalt stress

The aim of this study was to investigate the mechanism of cobalt (Co)stress damage on Medicago sativa as experiment materials,The effects of different concentrations (0,0.25,0.50,1.00,2.50,5.00 mmol/L CoCl2 )of Co on M.sativa (cv.Gannong No.3)seed germination and seedling physiological and bio-chemical characteristics were assessed.The results indicate that Co stress significantly inhibited seed germina-tion and seedling growth.Seed germination potential,germination rate,germination index,vigor index,seed-ling sprout length,radicle length,root activity and dry weight were significantly reduced with increasing cobalt concentration.The inhibitory effects of Co stress on germination potential was higher than that of cobalt stress on germination rate,and the inhibitory effects of Co stress on radical growth was higher than that on the plu-mule.Co significantly reduced the soluble protein content,soluble sugar content,proteolytic enzyme activity,superoxide dismutase (SOD),ascorbate peroxidase (APX),guaiacol peroxidase (GPX)and catalase (CAT)in seedling leaves.However free proline content increased dramatically at lower Co concentrations but declined at higher concentrations.At higher Co concentrations,O2 ·- (superoxide anion radical),OH · (hydroxyl radical), H2 O2 and malondialdehyde increased significantly.This illustrates that under high Co stress,the seedling an-tioxidant system activity and active oxygen scavenging ability of M.sativa decreased,inhibiting M.sativa seed germination and seedling growth.