STUDIES OF IRON TRANSPORT BY ARBUSCULAR MYCORRHIZAL HYPHAE FROM SOIL TO PEANUT AND SORGHUM PLANTS

The influence of an arbuscular mycorrhizal (AM) fungus on phosphorus ( P) and iron (Fe) uptake of peanut (Arachis hypogea L.) and sorghum (So rghum bicolor L.) plants was studied in a pot experiment under control led environmental conditions. The plants were grown for 10 weeks in po ts containing sterilised calcareous soil with two levels of Fe supply. The soil was inoculated with rhizosphere microorganisms only or with rhizosphere microorganisms together with an AM fungus (Glomus mosseae [Nicol. & Gerd.] Gerdemann & Trappe). An additional small soil compart ment accessible to hyphae but not roots was added to each pot after 6 weeks of plant growth. Radiolabelled P and Fe were supplied to the hyp hae compartment 2 weeks after addition of this compartment. After a fu rther 2 weeks, plants were harvested and shoots were analysed for radi olabelled elements. In both plant species, P uptake from the labelled soil increased significantly more in shoots of mycorrhizal plants than nonmycorrhizal plants, thus confirming the well-known activity of the fungus in P uptake. Mycorrhizal inoculation had no significant influe nce on the concentration of labelled Fe in shoots of peanut plants. In contrast, Fe-59 increased in shoots of mycorrhizal sorghum plants. Th e uptake of Fe from labelled soil by sorghum was particularly high und er conditions producing a low Fe nutritional status of the plants. The se results are preliminary evidence that hyphae of an arbuscular mycor rhizal fungus can mobilise and/or take up Fe from soil and translocate it to the plant.