镉对龙葵种子萌发及子叶抗氧化酶活性的影响

Effect of Cadmium on Seed Germination and Antioxidative Enzymes Activities in Cotyledon of Solanum nigrum L.

龙葵(Solanum nigrumL.)是Cd超累积植物,可用于植物冶金和Cd污染土壤的植物修复。超累积植物的生理基础研究有助于提高其对Cd的富集效率。龙葵种子在含有不同浓度CdCl(20、30、50、100、150、200μmol·L-1和300μmol·L-1)的琼脂培养基上萌发7d。结果表明,龙葵在200μmol·L-1和300μmol·L-1Cd时发芽率显著降低,而低浓度Cd(30～150μmol·L-1)胁迫下无显著差异;在Cd≥30μmol·L-1时,活力指数、发芽势均显著降低,幼苗的生长受到显著抑制。幼苗生长分析表明:在30～150μmol·L-1Cd处理下根长下降约17%～35%,显著低于200～300μmol·L-1Cd处理(下降79%～90%);株高随Cd浓度的升高逐渐下降。子叶抗氧化酶活性分析表明:100～150μmol·L-1Cd胁迫下,CAT和APX活性显著上升;在Cd胁迫下,SOD活性降低但维持在较高的活性水平。表明龙葵幼苗能忍耐小于150μmol·L-1Cd,抗氧化酶活性在抵抗Cd毒害方面发挥重要作用。

Hyperaccumulator species of the Solanum nigrum L. can accumulate Cd from soils where the concentrations are relatively low, and are therefore used for phytomining and phytoextraction of Cd contaminated soils. Basic studies on the physiology are needed to increase efficiency and uptake capacity of Cd by hyperaccumulators. The seeds of S. nigrum were germinated on the agar containing CdC12（0, 30, 50, 100, 150, 200 μmol L-1 and 300μmol. L-1） for 7 days. The results showed that germination rate was dramatically reduced at 200-300 μmol. L-1 Cd as compared to control, while no significant differences were found at 30-150 μmol.L-1 Cd. Additionally, vigor index, germination energy and the growth of seedling were reduced markedly in Cd concentrations exceeding 30 μmol L-1. Root elongation was declined by 17%- 35% at 30-150 μmol L-1 Cd and by 79%-91% at 200-300μmol.L-1 Cd, respectively; shoot height showed gradual decrease with the increasing Cd levels. Furthermore, the activities of catalase （CAT） and ascorbate peroxidase （APX） in S. nigrum cotyledon were strongly enhanced at 100-150 μmol. L-1 Cd, whereas superoxide dismutase（SOD） activity decreased, yet maintained a relatively high level. Taken together, these data indicated that S. nigrum might tolerate less than 150 μmol .L-1 of Cd and antioxidant enzymes play an important role in counteracting the deleterious effects of Cd.