菰和菖蒲对重金属的胁迫反应及其富集能力

通过盆栽实验研究了Cu—Zn—Ph-Cd复合污染条件下，菰和菖蒲的生长状况、生理特性及吸收和富集重金属的能力。结果表明，高浓度污染下菰和菖蒲不能存活；低、中浓度中菖蒲的生长受到抑制，菰各生长指标与对照相比差异不显著，表明菰对低、中浓度重金属的耐性强于菖蒲。随着污染浓度的增加，菰和菖蒲叶片叶绿索含量显著降低；菰叶绿素a／b值略有降低，菖蒲叶绿素a／b值显著降低；菰和菖蒲叶片脯氨酸含量、相对电导率显著升高，超氧化物歧化酶（SOD）、过氧化物酶（POD）活性在低浓度时升高，中浓度时降低。菰体内重金属含量为Zn〉Cu〉Pb〉Cd，菖蒲体内的含量为Cu〉Zn〉Pb〉Cd，且二者体内的重金属含量都随着污染浓度的增加而升高。菰和菖蒲对Cd的富集系数较大，地上部分（茎与叶）和地下部分（根与根状茎）均大于1；对Pb的富集系数较小，地上部分和地下部分均小于1。菰和菖蒲地下部分重金属含量均高于地上部分含量，二者根系对4种重金属都有较强的滞留效应，平均滞留率均大于50％。各处理中菰对重金属的吸收量均高于菖蒲。综合分析菰和菖蒲的生长、生理及富集重金属的能力，菰比菖蒲更适用于低、中浓度重金属污染水体的生态修复。

Stress responses and bioaccumulation of heavy metals by Zizania latifolia and Acorus calamus

Water contamination by trace metals is one of the main types of pollution in aquatic ecosystems. Aquatic plants can take up heavy metals from the environment. Their capability to absorb the elements differs both among species and their organs. Therefore, it is useful to identify various species and their organs which accumulate the greatest amounts of trace metals. The stress responses and metal bioaccumulation in combined treatments of copper, zinc, lead and cadmium by the emergent wetland plants Zizania latifolia and Acorus calamus were studied in pot experiments. Growth parameters, physiological indices and metal uptake by the two species were investigated. Results indicated that neither Z. latifolia nor A. calamus could survive in the highest concentrations employed. Compared to controls, plant height, number of roots and biomass of A. calamus significantly decreased in low and medium metal concentration treatments. No significant differences in plant height, number of roots and biomass of Z. latifolia could be demonstrated between the control and low and medium metal treatments. These growth differences between the two species might reflect that the innate metal resistance of Z. latifolia is higher than that of A. calamus. With increasing heavy metal concentrations, the chlorophyll content of both species decreased significantly, and the chlorophyll a/b rate decreased slightly in Z. latifolia and decreased significantly in A. calamus. SOD and POD activity increased in the low metal treatments and decreased in the mid-concentration treatment. Proline content and relative electrolyte leakage rate of the two species increased significantly. Copper, Zn, Pb and Cd concentrations in both species increased with increase of metals in soils, the rank order was Zn>Cu>Pb>Cd in Z. latifolia and Cu>Zn>Pb>Cd in A. calamus. The bio-concentration factor (BCF) for Cd in shoots (leaves and stems) and roots (rhizomes and roots) of the two species were both > 1, whereas the BCFs of Pb in shoots and roots were < 1. In both cases, concentrations of Cu, Zn, Pb and Cd in roots were higher than in shoots suggesting that these two species are basically excluder plants, translocating little metal from roots-shoot. There was a substantial retention function for roots of the two species to heavy metals, and their average retention rates were all greater than 50%. Overall uptake of Cu, Zn, Pb, and Cd by Z. latifolia was greater than by A. calamus in all treatments. Zizania latifolia could be suitable for phytopurification and phytoremediation of wastewater with low-medium concentrations of Cu, Zn, Pb and Cd.