Micro-pixe study of arbuscular mycorrhiza influence on elemental uptake by Berkheya Coddii

Abstract

Arbuscular mycorrhiza is a symbiotic association between fungi and plant roots. The major advantage of the symbiosis is an enhanced supply of essential nutrients to plants from the soil. At the same time mycorrhiza can have an impact on heavy metal transfer from the soil to the plants; this role is very dependent on the fungal strains and soil factors. The aim of the research is to assess the influence of different strains of AM fungi on the elemental uptake of Berkheya coddii, a Ni-hyperaccumulating South African plant. Glomus intraradices and fungi from rhizospheres of Senecio coronatus, and Berkheya coddii were used. B. coddii were cultivated on sterile soil under green-house conditions for 3 months. The root cross-sections were cryofixed for structure preservation and to maintain elements at their original locations. Elemental microanalysis using ion beam techniques - particle induced X-ray emission (PIXE) and proton backscattering (BS) - were used for analyzing root samples with the nuclear microprobe at Materials Research Group, iThemba LABS. Mycorrhiza increased the concentrations of non-essential and essential elements like P, Cl, K, Ca, Ni, Cu and Zn and non-mycorrhizal roots had increased concentrations of Fe and Cr. The results showed different elemental distributions throughout the root cross sections, and for most measured roots Ni was concentrated throughout the root for both mycorrhizal and non-mycorrhizal roots. Fe was mainly concentrated in the epidermis, Zn in the pith for mycorrhizal roots and in the epidermis for non-mycorrhizal roots.