模拟酸雨和Pb复合污染对芥菜型油菜的生理特性和Pb富集的影响

通过盆栽试验研究了模拟酸雨（pH分别为3.5、4.5、5.6）和Pb(0~2000 mg·kg-1）复合污染对芥菜型油菜紫叶芥的生理特性和Pb富集的影响.结果表明，在酸雨和Pb复合污染下，紫叶芥生物量和叶绿素含量均有不同程度的下降，叶和根中的超氧化物歧化酶（SOD）和过氧化物酶（POD）活性随着Pb含量和酸雨强度的增加是先升后降，脯氨酸含量随着Pb含量和酸雨强度的增加而升高.芥菜型油菜以通过调节抗氧化酶系统和提高脯氨酸含量来应对酸雨和重金属胁迫，芥菜型油菜对酸雨和Pb的复合污染有很强的耐受能力.芥菜型油菜根和地上部分Pb含量随Pb处理含量水平的增大而增加，其中，根对Pb的富集能力大于地上部分，酸雨能够促进芥菜型油菜对Pb的吸收.因此，在酸雨地区可以选用芥菜型油菜作为Pb污染土壤的修复植物.

Combined effects of artificial acid rain and Pb on physiological characteristics of Brassica juncea and its Pb uptake

Effects of artificial acid rain and Pb on the physiological characteristics and Pb uptake in the Indian mustard Brassica juncea were studied in pot experiments. Upon exposure to acid rain (pH=3.5, 4.5, 5.6) and/or Pb (0~2000 mg·kg-1), the biomass and the chlorophyll content of B. juncea decreased with increased Pb concentration, rain acidity or both. However, lower biomass and chlorophyll content were observed for the combined pollutants than with either alone, especially under more severe acid rain conditions and higher Pb concentrations. For rain of pH 5.6 or 4.5, the activities of superoxide dismutase (SOD) reached their peak in leaves when treated with 1200 mg·kg-1 Pb and in roots when treated with 800 mg·kg-1 Pb. For acid rain of pH 3.5 the activities of SOD reached their peak in leaves at 800 mg·kg-1Pb and in roots at 400 mg·kg-1 Pb. The peroxidase (POD) activities increased at first and decreased afterwards. POD activities were much greater in the roots than in the leaves, indicating that the protective enzymes in the roots eliminated most of the free radicals and mitigated the pressure on the leaves. However, some roots and leaves died when treated with severe artificial acid rain and high Pb concentrations, which resulted in decline of the POD activity. Meanwhile, the SOD and POD activities changed more rapidly in the roots than in the leaves, which indicated that the roots were more sensitive to the pollution. The proline and Pb contents in both leaf and root tissues of B. juncea usually increased with increased concentrations of Pb in soil and decreased pH values of the artificial acid rain. Exposure to acid rain with low pH promoted Pb uptake in B. juncea. The results suggest that the plant species Brassica juncea is suitable for use in phytoremediation of Pb\|contaminated soil in acid rain areas.