UPTAKE OF CD-109 BY ROOTS AND HYPHAE OF A GLOMUS-MOSSEAE TRIFOLIUM-SUBTERRANEUM MYCORRHIZA FROM SOIL AMENDED WITH HIGH AND LOW CONCENTRATIONS OF CADMIUM

Subterranean clover (Trifolium subterraneum L.) in symbiosis with Glom us mosseae (Nicol. & Gerd.) Gerdemann & Trappe was grown in compartmen ted pots. Side compartments were filled with soil where recently added (1 wk) radio-labelled cadmium (Cd) at three levels of non-labelled Cd could be accessed by either roots or arbuscular mycorrhizal hyphae. A ll treatments were replicated with non-mycorrhizal plants. After a gro wth period of 52 d roots and shoots were analysed for Cd-109, and leng ths of roots and hyphae in respective labelled compartments determined . Cadmium uptake by roots was not significantly influenced by the myco rrhizal status of the plant. Uptake of Cd from hyphal compartments was higher in mycorrhizal than in non-mycorrhizal plants, corresponding t o 96, 127 and 131% of that in non-mycorrhizal plants when 1, 10 and 10 0 mg Cd kg(-1) was added, respectively. A large proportion of the incr eased Cd content of mycorrhizal plants was sequestered in the roots. I t is concluded that extraradical hyphae of AM fungi can transport Cd f rom soil to plants, but that transfer from fungus to plant is restrict ed due to fungal immobilization. No reduction of hyphal growth into so il with up to 20 mg extractable Cd kg(-1) was observed.