Copper Tolerance In Artemisia Lavandulaefolia And Its Remediation Effect

Today, with rapid development of society and economy, heavy metal pollution has been an international difficult problem and has caused serious damages. Many countries have endeavored to clear away it for years. Although many heavy metals are essential chemical elements to plants'growth, for example, copper, they will become pollution when the contents in soil are higher than some a critical value. This pollution will do much harm to the plants, disturb their normal physiological metabolism as well as affect their growth, development and reproduction. However, there are also many species that can grow naturally in polluted soils and accumulate heavy metals. In the process of their growth, physical and chemical properties and enzymatic activities in soils are promoted by degrees. To accelerate the remediation of heavy metal pollution, we should study these tolerant plants and make clear the resistance mechanism and the remediation effect. In fact, such studies have attracted attentions worldwide.In this paper, A. lavandulaefolia, which belongs to Graminese, is chosen to be the experimental material, because of its widely arrangement, big biomass, strong roots, big biomass and primly adaptation to bad environment. Through hydroponic experiments, the author studies the coercion and damage of Cu pollution to the plant's growth. The result shows that under low concentration of Cu (2.5 mg·L-1), the growth of A. lavandulaefolia is stimulated. The height, weight, length and number of roots and pigments contents are higher than the contrast. However, high Cu concentrations inhibit the plant's growth. The indices of development decrease gradually, whereas permeability of cell membrane, generation rate of and MDA content increase. Anti-oxidative enzymes can clear up the active-oxygen and protect the cell membrane to some extent.To know more about the mechanism of resistance and the remediation effect, the author pots A. lavandulaefolia, then studies Cu accumulation, distribution in plants and Cu distribution, enzymes in soils. The main results are as follows: (1) With the Cu concentration increasing in soil, Cu contents in each part of plants increase as well. However,the absorption rate slow and the Cu contents of the whole plant approach its saturation point at high Cu concentration in soils. (2) Most of Cu is confined in root with low soluble and toxic forms when plant has a high Cu content. This mechanism can reduce Cu contents in leaf and stem relatively and protect the plant. (3) The growth of A. lavandulaefolia activates Cu fractions in rhizosphere soil, which can be demonstrated by the increasing of exchangeable, carbonate, Fe-Mn oxide fractions and the decreasing residual fraction. This change contributes to the absorption of Cu for the plant. (4) The growth of A. lavandulaefolia increases soil's pH and electric conductivity. And it also promotes enzyme activities in soils. (5) A. lavandulaefolia is not a hyperaccumulator, but it's endurance and the whole plant's Cu contents are high, besides it's rapid growth and big biomass, it is still a promising plant.