ROOT FACTORS STIMULATE P-32 UPTAKE AND PLASMALEMMA ATPASE ACTIVITY IN VESICULAR ARBUSCULAR MYCORRHIZAL FUNGUS, GIGASPORA-MARGARITA

Root-inducing (Ri) T-DNA transformed roots of carrot were used as the plant partner in a study of P-32 absorption and plasmalemma ATPase activity in the hyphae of the vesicular-arbuscular mycorrhizal fungus Gigaspora margarita Becker & Hall. Hyphae from germinating spores were grown in the presence or absence of root exudates and volatiles. In the presence of these root factors, P-32 isotope labelling occurred in hyphae, auxiliary cells and spores, while in the absence of these factors, the labelling only occurred in fungal spores. Similarly, ATPase activity appeared on the fungal plasmalemma only in the presence of root factors. The use of the ATPase inhibitor, diethylstilbestrol, demonstrated the importance of plasmalemma ATPase in the stimulation of hyphal growth of this obligately biotrophic fungus.