Endomycorrhizae were synthesized between Erica carnea and a fungus isolated from E. vagans. Inoculated and non-inoculated plants were grown for 6 months under controlled conditions. Inoculation provokes an important stimulation of the growth and flowering of E. carnea. Under the experimental conditions reported herein, the mycorrhizae formed during the 1st month remained localised and, after 6 months, the roots usually were not colonized by the fungus. It seems probable that colonization of the whole root system requires a growth substrate that favours mycelial growth.Macroscopic and microscopic characters of the mycorrhizae obtained were studied using light and scanning (SEM) and transmission (TEM) electron microscopy. The hyphae of the responsible fungus exhibit simple septa and Woronin bodies (ascomycetes). The intracellular hyphae are characterised by the abundance of lipid globules and the presence in SEM of electron-dense granules in the vacuoles. These hyphae are wrapped in a network of fibrils particularly at the penetration points but also observed on external hyphae. These mycorrhizae seem to survive for approximately 1 month only. The importance of the inoculum as nutritional source must not be neglected since similar stimulation of the plants was also produced by inoculation with an autoclaved slurry of mycelium. We suggest that not only mycorrhizal but also saprophytic rhizosphere fungi free, by simple autolysis of their mycelia, elements that are assimilable by the plant and doubtless play a role in the mineral nutrition of the Ericaceae.

No abstract

1986. Analysis by HPLC -mass spectrometry of the indole compounds released by the ectomycorrhizal fungus Hebelorna hiernale in pure culture. Can. J. Bot. 64: [1893][1894][1895][1896][1897]. Indole compounds released by Hebelorna hiernale Bres. in pure culture were studied by cultivating the fungus on a nutrient solution supplemented or not with 1 mM tryptophan. Analytical thin-layer chromatography revealed numerous indole compounds in 7-week-old culture filtrates obtained in the presence of tryptophan. Such compounds were isolated by preparative thin-layer chromatography and purified by high performance liquid chromatography. The most abundant of them, i.e., indolyl-3-acetic acid, indolyl-3-carboxylic acid, and indole-3-aldehyde. were identified by mass spectrometry. Indole-3-aldehyde and indolyl-3-carboxylic acid, which were detected in filtrates throughout the culture period, might result from breakdown of indolyl-3-acetic acid by fungal exocellular enzymes. ROUILLON, R., G. GAY, J. BERNILLON, J . FAVRE-BONVIN et G. BRUCHET. 1986. Analysis by HPLC -mass spectrometry of the indole compounds released by the ectomycorrhizal fungus Hebeloma hiernale in pure culture. Can. J . Bot. 64:1893-1897. La production de composCs indoliques par H. hiernale en culture pure a Ct C CtudiCe en cultivant ce champignon sur une solution nutritive contenant ou non du tryptophane 1 mM. De nombreux composCs indoliques ont Ct C mis en evidence par chromatographie sur couche mince dans les filtrats aprks 7 semaines de culture en prCsence de tryptophane 1 mM. Ces composCs ont Ctk isolCs par chromatographie sur couche mince prkparative et purifiCs par chromatographie liquide haute performance. Les plus abondants d'entre eux, c'est i dire l'acide indolyl-3-acCtique, l'acide indolyl-3-carboxylique et I'indole-3-aldChyde ont Ct C identifiks par spectromCtrie de masse. L'indole-3-aldChyde et l'acide indolyl-3-carboxylique, qui ont Ct C dktectCs tout au long de la culture, pournient provenir de la dkgradation de l'acide indolyl-3-acCtique par des enzymes fongiques exocellulaires.

Several forms of extracellular crystals have been observed in vitro on a semisynthetic culture medium. The conditions for their formation have not been determined. Their morphology and their localisation on the hyphal surface and in the culture medium have been investigated by means of scanning electron microscopy. These crystals have been identified as dehydrated calcium oxalate (Weddellite) using x-ray diffraction methods. Their high calcium content has been demonstrated with the scanning electron microprobe, by detecting the x-ray emission of calcium. The significance of calcium oxalate production by an ectomycorrhizal fungus is discussed.

The mycorrhizal synthesis between Dryas octopetala L. and two Agaricales from alpine area: Hebeloma alpinum (Favre) Bruchet and Hebeloma marginatulum (Favre) Bruchet, have been produced in the laboratory. Both fungi yielded normal fructification after 8 months in culture. After light and scanning electron microscopic examination, macro- and microscopical features of these mycorhizae are described. This symbiotic association, existing in the field between D. octopetala and those fungi typical of the alpine area, is discussed from an ecological point of view.