Study on Rhizosphere Functions of Athyrium Yokoscense and Arabis Flagellosa Comunity

在日本矿区，蕨类植物野胸草与阿拉伯鞭毛草形成了一个植被群落。前者在其组织中积累Cd、Pb和As，后者对Cd、Pb和Zn具有积累性质。然而，这两种植物的金属积累机制尚未得到充分阐明。本研究通过对横胸草和阿拉伯鞭毛草群落金属元素动态的研究，探讨了横胸草和阿拉伯鞭毛草群落根际重金属和砷的动员情况，以及重金属和砷的积累机制。盆栽试验中，土壤溶液中Cd、Pb、Zn的浓度在种植过程中也表现出类似的趋势，即阿拉伯蓟地（SS）土壤溶液中金属的浓度与非种植地的趋势相似，在种植8周后逐渐升高，而后基本保持不变，而猪蹄草地（HN）或阿拉伯蓟与阿拉伯蓟混合地（HN+SS）土壤溶液中金属的浓度在种植8周后仍持续升高。因此，与阿拉伯鞭毛草样地相比，种植胸草样地（HN和HN+SS）后13周土壤溶液中Cd、Pb和Zn含量较高。认为胸腺根分泌渗出物，促进了根际镉、铅、锌的迁移。种植期内各样地土壤溶液砷浓度均极低（< 27μgL^<-1>）。可能是由于As以阴离子形式存在，所以在低ph条件下被土壤强烈吸附。另一方面，在HN和HN+SS地块的土壤溶液中检测到马来酸、柠檬酸和富马酸。综上所述，胸脯草根系分泌物可促进根际镉、铅和锌的迁移，提高其在土壤溶液中的浓度。

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.