| Roots of 23 species of terrestrial orchids were examined for colonization by mycorrhizal symbionts which were obtained in pure culture, and identified. Almost all orchid plants collected were mycorrhizal, and were associated with the genera Ceratorhiza, Epulorhiza and Moniliopsis. Ceratorhiza spp. were the most frequently isolated mycorrhizal taxa and a new species is described (Ceratorhiza praeclara sp. nov.). E. repens, E. anaticula and E. albertaensis were also isolated. Many plants were colonized by more than one mycorrhizal symbiont (often an Epulorhiza sp. and a Ceratorhiza sp.). Specificity of the orchids for single species (or even genera) of fungi, therefore, is unlikely with the exception of Corallorhiza trifida which was consistently mycorrhizal with a clamped yellow fungus, found also to form ectomycorrhizas with Pinus contorta in vitro. Seeds of 11 species germinated, and at least one protocorm of each contained pelotons. The mycorrhizal fungi for five of these species included clamped basidiomycetes. The chance of encounter between seeds and the appropriate mycorrhizal symbiont may be low, as many seeds germinated but were not colonized. Only mycorrhizal protocorms developed further. Few basidiomycetes were isolated from the seeds, but several strains (Epulorhiza sp.) were unlike those from the roots of mature orchids. Mortality of germinating seeds due to fungal parasitism was high. Development of the orchids was slow. Successfully colonized protocorms, with the exception of a few individuals of three species, did not progress beyond the organization of an apical meristem during the first growing season. (Abstract shortened by UMI.). |
