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• Arachnitis uniflora, a myco-heterotrophic plant species, has fleshy tuberous roots colonized by the arbuscular mycorrhizal fungal genus Glomus (Phylum Glomeromycota). These roots produce apical and lateral propagules, both reported here for the first time. The objective of the study was to characterize the ontogeny and structure of the propagules, and to determine their function. • Scanning electron microscopy, laser scanning confocal microscopy and light microscopy were used to study the ontogeny and structure of the propagules. • Propagules developed either from cortical parenchyma cells or from cells immediately beneath the root cap; they developed a shoot meristem and cells in the basal region which were colonized by various fungal structures including hyphae and vesicles. • These propagules may detach from the roots, establishing new plants. [ABSTRACT FROM AUTHOR]

• The annual developmental cycle of tuberous roots ofRanunculus asiaticuswas studied with respect to structure and content of their cells, to understand how these roots are adapted to desiccation, high temperature and rehydration.• Light microscopy, histochemical analysis, and protein analyses by SDS-PAGE were employed at eight stages of annual root development.• During growth and maturation of the roots, cortical cells increased in size and their cell walls accumulated pectin materials in a distinct layer to the inside of the primary walls, with pits between adjoining cells. The number of starch granules and protein bodies also increased within the cells. Several discrete proteins accumulated. Following quiescence and rehydration of the roots there was a loss of starch and proteins from the cells, and cell walls decreased in thickness.• The resurrection geophyteR. asiaticuspossesses desiccation-tolerant annual roots. They store carbon and nitrogen reserves within their cells, and pectin within the walls to support growth of the plant following summer quiescence and rehydration.New Phytologist(2005)doi: 10.1111/j.1469-8137.2004.01306.x© New Phytologist(2005) [ABSTRACT FROM AUTHOR]

Seeds of the orchid species, Spiranthes sinensis (Pers.) Ames, were sterilized and germinated in vitro with the symbiotic fungus Ceratobasidium cornigerum (Bourdot) Rogers. Colonized embryos developed into protocorms and these were examined for changes in microtubule arrays, after initial invasion of fungal hyphae into embryos and during peloton formation and degradation. Methods utilized to detect microtubules included immunofluorescence combined with laser scanning confocal microscopy, conventional transmission electron microscopy combined with morphometric analysis, and immunogold labelling. Microtubules were regularly found in close association with intracellular hyphae and degraded hyphal masses. Cortical microtubules disappear during peloton formation but reappear in cells that show fungal lysis. With conventional transmission electron microscopy and immunogold labelling the microtubules associated with fungal hyphae and degenerated hyphal masses were located close to the perifungal membrane that separates fungal hyphae from protocorm cytoplasm. [ABSTRACT FROM AUTHOR]

The morphology and anatomy of ectomycorrhizas of Rhizopogon arctostaphyli, R. elIenae, R. flavofibrillosus, R. accidenalis, R. rubescens, R .smithii, R. subcaerulescens and R. truncatus synthesized on Ponderosa pine (Pinus ponderosa) in glasshouse conditions using spore slurries, are described and compared. All species produced a well-developed Hartig net, and a well-developed fungal mantle. The mantles of R. arctostaphyli. R. smithii and R. subcaerulescens ectomycorrhizas were two-layered with outer mantle hyphac of wider diameter than inner mantle hyphae. The mantle of R. subcaerulescens ectomycorrhizas also had distinctive peg-like structures (cystidia) along peripheral hyphae. Rhizopogon truncatus ectomycorrhizas were tuberculate in morphology and had a rind-like mantle enclosing adjacent roots. In addition, several species exhibited crystal inclusions in the outer mantle, presumably at the interface between mantle and soil. [ABSTRACT FROM AUTHOR]

The article focuses on the early stages in colonization of Allium porrum roots by the vesicular-arbuscular mycorrhizal fungus, Globus versiforme. Leek roots were colonized by the vesicular mycorrhizal fungus Glomus versiforme Berch. External hyphae were of varying sizes and had a single-layered wall surrounding a vacuolate cytoplasm. Intra-hyphal hyphae were frequent in the extraradical mycelium. Some external hyphae formed small branches which initiated simple appressoria over the outer tangential wall of epidermal cells.

summary: Seedlings of Pinus resinosa Ait. grown in test tubes were inoculated with the ectomycorrhizal fungus Paxillus involutus Fr. and, one day later, with a spore suspension of the root pathogenic fungus Fusarium oxysporum Schlecht emend, Sny. & Hans f.sp. pini. Controls consisted of seedlings inoculated with plugs of sterile modified Melin Norkrans medium and F. oxysporum. Seedling survival was counted, sporulation of F. oxysporum was measured, and ethanol extractions of the rhizosphere were made, 1, 2, 3, 4, 5, 6, 8, 10 and 14 d after inoculation with the pathogen. The ethanol extractives were concentrated and assayed for fungitoxic activity by measuring the germination of F. oxysporum microconidia. Dead seedlings were first observed 3 d after inoculation with the pathogen. Sporulation of F. oxysporum was reduced significantly 3 d after seedling inoculation with P. involutus when compared with controls lacking P. involutus. The fungitoxic activity of the rhizosphere of the seedlings inoculated with P. involutus was greater than the fungitoxic activity of the rhizosphere of control seedlings, increasing strongly 2.4 d after inoculation with the pathogen. Suppression of Fusarium root rot by P. involutus may, therefore, be the result of antibiosis by this ectomycorrhizal fungus. [ABSTRACT FROM AUTHOR]

Nuclear DNA content of root cortical cells of Lotus pedunculatus Cav., Lotus corniculatus L. and Trifolium pratense L. was determined using a microspectrophotometer. Infected and uninfected roots from plants which had been colonized with the fungus, Glomus versiforme (Daniels and Trappe) Berch and roots from non-inoculated plants were compared. Relative DNA contents for cortical cell nuclei of the three hosts were within the 2-4C range for uninfected root cells. There was no evidence that the VAM fungus, G. versiforme, induced endoreduplication of cortical cell nuclei during infection of these forage legumes. Nuclear enlargement reported in other studies of VAM colonization is likely to involve mechanisms of nuclear enlargement other than DNA endoreduplication. [ABSTRACT FROM AUTHOR]

The ectomycorrhizal fungus Paxillus involutus Fr. was grown in the presence of root exudate of Pinus resinosa Ait. for two weeks. The effect of root exudate on the synthesis of ethanol-soluble antifungal compounds by P. involutus was determined by a bioassay based on microconidial germination of Fusarium oxysporum Schlecht emend, Sny. & Hans f.sp. pini. Cultivation of P. involutus on root exudate led to a greater than two-fold increase in fungitoxic activity when compared to cultivation on modified Melin-Norkrans medium in Petri dishes. Inoculation of P. resinosa root exudate with both P. involutus and a spore suspension of F. oxysporun: led to an 80% suppression of the sporulation of F. oxysporum when compared to controls lacking P. involutus. The increased resistance of P. resinosa P. involutus associations to Fusarium root rot may, therefore, be the result of biosynthesis of antifungal compounds by P. involutus which is stimulated by P. resinosa root exudate. [ABSTRACT FROM AUTHOR]

Ectomycorrhizas were synthesized in growth pouches between Eucalyptus pilularis Sm. and Hydnangium carneum Wallr. in Dietr. Colonization of lateral roots occurred within 14 d after inoculation with the development of a dense white mantle and a paraepidermal Hartig net. Cystidium-like structures and unusual hyphal coils were present on the surface of the mature mantle. The mantle consisted of distinctive outer and inner portions with small, uniform hyphae comprising the outer mantle and much enlarged and modified hyphae in the inner mantle. Granular deposits were abundant primarily in the inner mantle hyphae as shown by light and fluorescence microscopy. These granules were shown to be polyphosphate through cytochemical tests and the use of energy dispersive X-ray microanalysis. Phosphorus and calcium were the main elements identified in these granules. [ABSTRACT FROM AUTHOR]

Twenty half-sib families from within each of two populations of Medicago sativa L. (Pioneer 530 and OAC 78-101) were assessed for differences in ability to form vesicular- arbuscular mycorrhizas (VAM) when grown in association with one VAM fungal species, Glomus versiforme (Daniels and Trappe) Berch. The families were grown under controlled environmental conditions using a culture-pot system. Roots were cleared, stained and assessed for percent colonization. From the analyses of variance, the genetic variance and heritability of percent Colonization were estimated. The mean percent colonization was 5.8 and 6.8%, for the Pioneer 530 and OAC 78-101 populations, respectively. Significant (P < 0.05) differences in percent colonization were detected among half-sib families derived from Pioneer 530 but not among half-sib families derived from OAC 78-101. Significant (P < 0.05) pot and run effects were detected in the latter experiment which may have masked differences among the families. The estimate of narrow-sense heritability of percent colonization in the Pioneer 530 population was 18.8%, and the expected response to selection for percent colonization, if the top 10% of the population was selected, was 2.2% per cycle. This indicated that there was good potential for improving the extent of VAM colonization in the population of alfalfa. Further studies of host genotype VAM symbioses are warranted. [ABSTRACT FROM AUTHOR]

Ectendomycorrhizas were synthesized between Pinus resinosa Ait. (red pine) and the E-strain fungus, Wilcoxina mikolae var. mikolae (Yang and Wilcox) Yang & Korf in growth pouches. A rudimentary mantle consisting of a few hyphae embedded in a matrix was formed. Although a Hartig net was formed, the predominant phase consisted of intracellular hyphae in cortical cells of lateral and main roots. Cortical cells in basal portions of lateral roots showed various degrees of senescence, and hyphae in these cells were highly vacuolated. [ABSTRACT FROM AUTHOR]