A Quantitative Study of the Spores and Anatomy of Mycorrhizas Formed by a Species of Glomus, With Reference to Its Taxonomy

Abstract

The development of spores and sporocarps was studied in two isolates of a species of Glomus collected in Western Australia. The isolates, which had been maintained in pot culture, differed slightly in the size range of spores and in the relationship between spore size and the development of the peridium. Anatomical characteristics of mycorrhizas of three pasture species (Trifolium subterraneum, Erodium botrys and Lolium rigidum) formed with this species of Glomus were essentially the same and were largely unaffected by nitrogen supply. The hyphae in nitrogen-deficient plants were slightly wider than those in nitrogen-adequate plants of T. subterraneum and E. botrys. The effect of phosphorus supply on the anatomy of mycorrhizas formed by this fungus and T. subterraneum was studied with time. Phosphorus supply had no effect on the formation of arbuscles, the density of hyphae within infected roots, or the morphology of the branching pattern of the endophyte hyphae within the root. However, phosphate added above that required for maximum plant yield eliminated vesicle formation. Anatomical characteristics of the mycorrhizas changed little with time except for arbuscle number, which decreased markedly between 29 and 50 days after sowing. We concluded that the anatomy of vesicular arbuscular mycorrhizas formed by a particular endophyte species grown under a range of conditions may not be as variable as has been generally assumed. There is scope for identification of species of endophyte within plant roots. Furthermore, some features of infection morphology could prove to be useful for taxonomic purposes.