Study On Physiological Response And Enrichment Characteristics Of Zinc,Copper In Lantana Camara L.

Heavy metal pollutant in soil has become a serious problem in agricultural production and human health. One effective and eco-friendly solution is the phytoremediation. However, here are many defects in plants used for phytoextraction. including low biomass, poor tolerance, low enrichment, and poor ornamental, etc. It can not fulfill requirements for for soil remediation. Therefore, searching for new plants with high biomass, strong tolerance and high enrichment has been the key part of phytoremediation. In this study, Lantana camara L., which has been found in lead-zinc mining area of Sichuan, was used as the experimental material. A pot experiment was conducted to investigate its growth, Zn/Cu uptake and enrichment characteristics. Furthermore, this study researched its tolerance mechanism from the aspects of Zn/Cu's chemical form, subcellular distribution and antioxidant enzyme activities of the plant, objective is to explore the ability of L. camara to repair Zn/Cu contaminated soil. The main results showed that:(1) Zn concentrations in soil at 0?1500 mg/kg can contribute to the growth of L. camara, but opposite effects were observed when Zn concentrations were above the level. And the superoxide dismutase, peroxidase, catalase and ascorbate peroxidase activities in both roots and leaves of L. camara were significantly enhanced when the Zn concentrations in soil reached 0?1500 mg/kg, the oxidative stress induced by Zn was relieved, and the growth of L. camara was promoted. However, the activities of antioxidant enzymes in roots and leaves decreased when the Zn concentrations in soil were above the level, the plant suffered severe oxidation damage and growth inhibition.(2) Under 0?500 mg/kg Zn treatment, higher Zn concentrations in shoots rather than in the roots were detected. However opposite results were found when the Zn concentrations in 1000?3000 mg/kg, and the roots hindered the translocation of Zn. The highest Zn concentrations in roots and shoots reached 1576 mg/kg and 1538 mg/kg, respectively. And the highest accumulation amount of Zn in roots and shoots were 1.6 mg/plant and 15 mg/plant. respectively. L. camara showed high accumulation ability towards Zn. However, when the Zn concentrations in soil were above 2500 mg/kg, the accumulation amount of Zn in L. camara has decreased slightly.(3) Zn was predominated with the forms of water extracs and low toxicity NaCl and HAc extracts in root, leaf and stem of L. camara. Moreover,32%?45%,43%?46% and 33%?45% of Zn was stored in cell wall in roots, stems and leaves, respectively. And 39%?52%,32%?49% and 32%?44% of Zn was stored in soluble fraction, respectively. A small amount of Zn was stored in the organelle.(4) Under the Zn treatment, rhizosphere soil pH of L. camara decreased, the percentage of acid extractable Zn increased, and Zn was activated. When the Zn concentrations in soil were 0?1500 mg/kg, the catalase, urease, phosphatase and sucrase activities in soil increased, while the catalase, urease, and phosphatase activities were inhibited when the Zn concentrations in soil were over the level. They were sensitive to the toxicity of Zn.(5) Cu concentrations in soil at 0?600 mg/kg can contribute to the growth of L. camara, but opposite effects were observed when Cu concentrations were above the level. And the superoxide dismutase, peroxidase, catalase and ascorbate peroxidase activities in both roots and leaves of L. camara were significantly enhanced when the Cu concentrations in soil reached 0?1500 mg/kg, the oxidative stress induced by Cu was relieved, and the growth of L. camara was promoted. However, the activities of antioxidant enzymes in leaves decreased when the Cu concentrations in soil were above the level, leaves suffered severe oxidation damage and the shoot growth inhibition.(6) Under the Cu treatment, Cu concentrations in the plant were about 12?59 mg/kg, and were higher in roots than in shoots, root hindered the absorption and translocation of Cu. The highest accumulation amount of Cu in roots and shoots were 80 ?g/plant and 407 ?g/plant. respectively. L. camara showed high accumulation ability to Cu.(7) Cu was predominated with the forms of low toxicity NaC1, HAc and HC1 extracts in root and leaf of L. camara, but the Cu in stem was predominated with the forms of NaCl extracts and high toxicity ethanol extracts. Moreover.37%?64% of Cu was stored in soluble fraction in roots, and 40%?43% and 29%?38% of Cu was stored in cell wall in stems and leaves, respectively. A small amount of Zn was stored in the organelle.(8) Under different Cu treatments, rhizosphere soil pH of L. camara decreased, the percentage of acid extractable Cu increased, and Cu was activated. When Cu concentrations in soil were 0-100 mg/kg, the phosphatase and sucrase activities in soil were increased, but the catalase and urease activities showed no obvious difference, while the catalase, urease, and sucrase activities were inhibited when the Cu concentrations in soil were over the level. They were sensitive to the toxicity of Cu.In summary, L. camara has the strong tolerance and accumulation ability towards Zn and Cu, which is suitable for restore the Zn/Cu contaminated soil when Zn concentration is below 2500 mg/kg and Cu concentration is below 1800 mg/kg. The tolerance mechanism of L. camara includes root inhibition, soluble fraction and cell wall immobilization, as well as antioxidant system response.