Intraspecific differences of arbuscular mycorrhizal fungi in their impacts on arsenic accumulation by Pteris vittata L.

It has been shown that Pteris vittata, an arsenic hyperaccumulator, could be colonized by arbuscular mycorrhizal (AM) fungi either in controlled conditions or at field sites. However, physiological mechanisms of AM fungi influencing As accumulation and tolerance in the plant are not fully elucidated. Two predominant fungal species, Glomus mosseae and Glomus geosporum, and a rapidly sporulating fungal species, Glomus etunicatum, associated with P. vittata were isolated from As-contaminated soils. Two uncontaminated isolates, G. mosseae and G. etunicatum, served as reference isolates. Based on germination of spores exposed to elevated As, Pb and Zn concentrations, two contrasting isolates of G. mosseae were selected to investigate As accumulation in two populations of P. vittata [from an uncontaminated site of Hong Kong (HK) and an As-contaminated site located in Jinchuantang (JCT) of Hunan Province, China, respectively] under hydroponic culture and pot trials. At lower levels of As exposure (50-200 microM), both uncontaminated and metal-contaminated isolates of G. mosseae significantly increased short-term As influx into roots of P. vittata. However, at higher levels of As exposure (400-1000 microM), only uncontaminated isolates significantly increased short-term As influx into roots. When growing on 100mg As kg(-1) soils, uncontaminated isolates exhibited a higher level of colonization in roots of P. vittata than metal-contaminated isolates and only the former significantly increased As accumulation in roots of HK population and in fronds of JCT population. It was concluded that there were intraspecific differences of AM fungi in their impacts on As accumulation by P. vittata.