Abstract
Spore germination of seven species of ectomycorrhizal fungi was studied under different conditions. Spores of most species tested did not germinate on laboratory media without stimulators. Various stimulators were tested and the greatest activation was that by Pseudomonas stutzeri which was obtained from fruitbodies of Hebeloma crustuliniforme and stimulated about 21% of spores of that fungus. Effects of plant roots on spore germination were studied in the laboratory and in soil. In mineral salts medium, spores of Paxillus involutus were stimulated by five of seven tree species and one of four non-tree species tested. Spores of Laccaria laccata and H. crustuliniforme were stimulated by birch and pine only, while those of lactarius turpis and Amanita fulva were only slightly stimulated by birch roots. Birch was more stimulatory and the highest germination (30%) was that of H. crustuliniforme at 0-1 mm from the root edge. In soil, spores of P. involutus only, of the seven species tested, were stimulated to germinate near roots of birch and spruce in steamed and untreated soils. Birch stimulated up to 96% of spores to germinate in untreated birch wood soil. Spruce had much less effect on germination in either steamed or untreated soil. The majority of germ tubes grew towards the roots. Exudate from roots of seedlings of birch previously grown in soil was active in stimulating germination of H. crustuliniforme, but not of the other six species tested. Activity of the root exudate was associated with the ninhydrin-positive fraction. The role of the basidiospores of the test fungi in initiating mycorrhizas in soil was also studied. Spores of P. involutus and L. laccata established mycorrhizas with birch, but not spruce or pine roots. Spores of the other five species tested did not establish mycorrhizas with any of the plant tested.