Mycorrhizal fungi modify element distribution in gametophytes and sporophytes of a fern Pellaea viridis from metaliferous soils

In the present study, the element distribution within mycothallic and nonmycothallic gametophytes and the early stages of sporophyte development of Pellaea viridis (Pteridaceae) were investigated. Gametophytes of this fern were collected from soil samples originating in the ultramafic area of the Agnes Mine near Barberton, South Africa. The gametophytes were grown on both the original soil and on a plant growth substratum obtained from the local botanical garden. Gametophytes and young sporophytes grown on substratum inoculated with Glomus tenue or non-inoculated were freeze-dried, and the distribution of elements was studied using micro-PIXE. The GeoPIXE II software package was used for quantitative elemental mapping complemented by data extracted from arbitrarily selected micro-areas. The obtained results suggest that although the fern itself avoids the uptake of large amounts of heavy metals, increased levels of Ni, Cr, Fe, Co and Ti were found in the part of the gametophyte that hosted the fungal endophyte. This finding suggests that the fungus might be active in the immobilisation of certain potentially toxic metals that are taken up from the soil by the plant, although other mechanisms cannot be excluded. For the first time, precise, quantitative measurements of the concentration of individual elements in the fern gametophytes and young sporophytes were obtained, along with their distribution within the plant parts.