| Research Abstract |
Athyrium yokoscense, a fern plant, forms a vegetation community with Arabia flagellosa in mining area of Japan. The former accumulates Cd, Pb, and As in its tissues and the latter has accumulation nature to Cd, Pb, and Zn. However, the metal accumulation mechanism of both plants has not been sufficiently clarified. In this study, by examining the dynamic state of the metallic elements in Athyrium yokoscense and Arabis flagellosa community, the mobilization of the heavy metals and arsenic in rhizosphere of Athyrium yokoscense and Arabis flagellosa community, as well as the accumulation mechanism of the heavy metals and arsenic, were investigated. In a pot experiment, Cd, Pb and Zn concentration of soil solution showed similar tendency during plantation, i.e., the metals concentration of soil solution in Arabis flagellosa plot(SS)showed similar trend with the non-plant plot, increasing up till the 8th week then became almost constant, but those of Athyriurn yokoscense plot (HN) or Athyrium yokoscense and Arabis flagellosa mix plot (HN+SS) increased continually even after 8 weeks. Thus, compared with Arabia flagellosa plot, soil solution of the plots (HN and HN+SS) planting Athyrium yokoscense contained higher Cd, Pb and Zn concentration in the latter 13 weeks. It was supposed that roots of Athyrium yokoscense secreted exudates, and enhanced mobilization of Cd, Pb and Zn in rhizosphere. Arsenic concentration of the soil solution was extremely low (< 27μgL^<-1>) in all plots during the planting periods. It probably because As occurs as anion so it is strongly adsorbed in soil at low pH. On the other hand, maleic acid, citric acid and fumaric acid were detected in the soil solution of HN and HN+SS plots. It is concluded that root exudates of Athyrium yokoscense might enhanced mobilization of Cd, Pb and Zn in the rhizosphere, and elevated their concentration in the soil solution.
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