VA MYCORRHIZAL SPORES FROM 3 SPECIES OF ACAULOSPORA - GERMINATION, LONGEVITY AND HYPHAL GROWTH

The spores of three species of Acaulospora were examined to compare th eir rate of germination, the effect of long term storage on their viab ility, their tolerance to disturbance, and the length of hyphae they p roduced. The rate of germination of Acaulospora laevis was initially s lower than that of the other two species but all species reached maxim um germination after 21 d incubation. For each fungus only a small pro portion of spores stored for 2 months in dry pot culture soil germinat ed. After storage for 4-6 months most spores germinated indicating tha t dormancy, which was most marked in A. laevis, was overcome. Spores w ere then germinable for many months. The larger spore of A. laevis pro duced greater hyphal length per spore and was more sensitive to physic al disturbance than the smaller spores of Acaulospora trappei and Acau lospora sp. (WUM 18-1). None of the three fungi were able to colonize living roots when dead mycorrhizal root pieces were used as an inoculu m source. A technique to allow the distinction between newly formed sp ores and those present in the original inoculum was developed.