镉、汞胁迫对桔梗种子萌发、幼苗生理生化特性及镉、汞含量的影响

Respones of Seed Germination and Physiological,Biochemical Characteristics and Cd,Hg Content of Platycodon grandiflorum Seedling to Cadmium and Mercury Stress

为探讨重金属对植物种子萌发、幼苗生长及生理生化的影响,本试验以桔梗种子为试验材料,采用培养皿滤纸发芽法,研究桔梗种子萌发、幼苗生长及生理生化特性对不同浓度镉(Cd)、汞(Hg)胁迫的响应特征。结果表明,低浓度Cd^(2+)和Hg^(2+)(≤20 mg·L^(-1))处理对桔梗种子的发芽势和发芽率影响不大;Cd^(2+)浓度≥30 mg·L^(-1)、Hg^(2+)浓度≥40 mg·L^(-1)时桔梗种子的发芽势和发芽率显著降低;Cd^(2+)浓度≥20 mg·L^(-1)、Hg^(2+)浓度≥30 mg·L^(-1)时桔梗种子的发芽指数显著降低;桔梗种子的活力指数随着Cd^(2+)和Hg^(2+)浓度的增加而降低。桔梗萌发幼苗的根长、株高和鲜重随着Cd^(2+)和Hg^(2+)浓度增加而降低;可溶性糖含量随着Cd^(2+)和Hg^(2+)浓度增加呈先增加后降低的趋势;可溶性蛋白含量随着Cd^(2+)浓度增加呈先增加后降低又增加的变化,随着Hg^(2+)浓度增加而增加且保持在较高水平。Cd^(2+)处理后,桔梗幼苗的丙二醛(MDA)含量呈先降低后增加趋势;Hg^(2+)处理后,桔梗幼苗的MDA含量增加。超氧化物歧化酶(SOD)活性随着Cd^(2+)和Hg^(2+)浓度增加呈先升高后降低的趋势;过氧化物酶(POD)活性随着Cd^(2+)浓度增加呈先升高后降低再升高的变化,随着Hg^(2+)浓度增加呈先降低后升高趋势。桔梗幼苗地上部和根部的Cd、Hg含量均随着Cd^(2+)和Hg^(2+)浓度增加而增加。综上,较低浓度的Cd^(2+)和Hg^(2+)对桔梗种子萌发影响不大,但会抑制幼苗生长;较高浓度Cd^(2+)和Hg^(2+)抑制种子萌发和幼苗生长,并引起生理生化变化及植株体内Cd、Hg含量的增加。本研究为阐明重金属胁迫对桔梗幼苗生长影响的机理提供了理论依据。

To investigate effect of heavy mental on seed germination,seedling growth and physiological,biochemical characteristics of plant,the response of seed germination,seedling growth and physiological,biochemical characteristics of Platycodon grandiflorum under different concentrations of cadmium and mercury stress were studied by mean of petri dish filter paper method. The results showed that low concentration of Cd^2＋ or Hg^2＋（ ≤20 mg·L^-1） treatment had little effect on the germination energy and germination rate,while the germination energy and germination rate dropped significantly when the concentration of Cd^2＋ was higher than 30 mg·L^-1 and the concentration of Hg^2＋ was higher than40 mg·L^-1. The germination index dropped when the concentration of Cd^2＋was higher than 20 mg·L^-1 and the concentration of Hg^2＋ was higher than 30 mg·L^-1,and the vitality index dropped with the increasing of the Cd^2＋and Hg^2＋ concentration. The root length,plant height and fresh weight was reduced with the increasing of the Cd^2＋ and Hg^2＋ concentration. The soluble sugar content increased first decreased then with the increasing of the Cd^2＋and Hg^2＋ concentration,however the soluble protein content increased first,then and increased finally with the increasing of the Cd^2＋ concentration,but increased with the Hg^2＋ concentration and were keeping at high level. The MDA content dropped first increased then after by Cd^2＋ treatment and incrased after by Hg^2＋ trteatment. The SOD activity rose first then declined with the increasing of the Cd^2＋ and Hg^2＋ concentration,while the POD activity rose first,then declined and rose at last with the increasing of the Cd^2＋ concentration,declined first then rose with the increasing of the Hg^2＋ concentration. The Cd,Hg content of the above ground and root increased with the increasing of the Cd^2＋ and Hg^2＋ concentration. In conclusion,the low concentration of Cd^2＋ and Hg^2＋ has little effects on seed germination but inhibited the growth of seedlings,higher concentration of Cd^2＋ and Hg^2＋ inhibited the seed germination and seedling growth,biochemical changes and increased the Cd,Hg content. This study provides a theoretical basis to elucidate the mechanism of heavy metal stress to seedling growth of Platycodon grandiflorum.