Patterns of Root Colonization in Epacridaceous Plants Collected from Different Sites

Root colonization was studied in ten species of the Epacridaceae at three sites in Victoria by morphological and cross-inoculation experiments. The sites and genera chosen were Cranbourne [ Epacris impressa Labill. and Leucopogon ericoides (Smith) R. Br.] and Rye [ L. parviflorus (Andrews) Lindley] on the Mornington Peninsula, and the Grampians [Astroloma conostephioides (Sond.) Benth., A. humifusum (Cav.) R. Br., A pinifolium (R. Br.) Benth, Brachyloma daphnoides (Smith) Benth., E. impressa, E. impressa var. grandiflora Benth. and Styphelia adscendens R. Br.] in western Victoria. For morphological studies, samples of roots from each species at each site were cleared and stained and examined microscopically. For cross-inoculation studies, cuttings from each site were struck in potting medium inoculated with soil from the same and other sites. The ericoid mycorrhizae in the roots of plants found at or grown in Cranbourne and Rye soils were similar. Both were significantly different from the internal hyphae found in the roots of plants found at or grown in Grampians soils, which were three times larger in diameter and formed dense coils which filled the host cell and invaded adjacent epidermal cells. This suggests that more than one fungus is involved in the relationships, that the Mornington Peninsula sites had a different fungus from the Grampians site and that host specificity is low. Vesicular structures were also found commonly on plants at the Grampians site, in contrast with other sites.