Vesicular-arbuscular mycorrhizas in white clover: a scanning electron microscope and X-ray microanalytical study

Abstract

Seedlings of white clover (Trifolium repens L.) were inoculated with several strains of mycorrhizal fungi and were cultured for sufficient time to allow the fungal endophytes to develop and mature. The roots were then subjected to a simple freezefracture, freeze-dry procedure in preparation for scanning electron microscopy and X-ray microanalysis. The morphology of the endophytes was observed and qualitative X-ray data were obtained indicating an accumulation of elements within mature arbuscles. Evidence of endophyte breakdown, accompanied by a reduction of the expected phosphorus concentrations, was also obtained and its implications are discussed.

Occurrence of manganese-rich inclusions in the root cortex of white clover

“…In detail, the inclusions appeared as a textured matrix (Figs 2, 3), which when analysed was found to contain consistently high concentrations of manganese (Fig. 4), an element not normally detected in this plant material (Walker & Powell 1979).…”

“…After being freeze-dried by a method described by Humphreys (1975), the segments were mounted on SEM· sample holders and were coated with carbon and aluminium layers of a nominal thickness of 10 nm each .. The samples were then examined in a Cambridge Stereoscan IIA equipped with an EDAX 707A X-ray microanalyser (Walker & Powell 1979).…”

“…To cite this article: Graham D. Walker (1979) Occurrence of manganese-rich inclusions in the root cortex of white clover, New Zealand Journal of Botany, 17:1, 1-3, DOI: 10.1080/ 0028825X.1979.10425154 To link to this article: http://dx.doi.org/10.1080/0028825X.1979.10425154…”

Etude de l'origine et de la répartition des granules vacuolaires dans les hyphes d'une endomycorhize à vésicules et arbuscules

“…En effet, Ies granules sont absents ou tres reduits dans Ies branches de I'arbuscule, formations directement impliquees dans les echanges actifs entre les partenaires. II est d'autre part bien connu que Ie champignon symbiote transfere de grandes quantites de phosphore a Ia plante-h6te (Harley, I 969 ;Sanders et Tinker, 1971 ;Bowen et al, 1975 ;Callow et al, 1978 ;Walker et Powell, 1979). En fait, dans une endomycorhize active, les granules de polyphosphate, resultant de Ia polymerisation de phosphore preleve dans le sol, sont transportes jusqu'aux arbuscules par les hyphes intercellulaires (Strullu et al, 1981 …”

“…Comme toutes les mycorhizes, elles ameliorent de maniere tres sensible Ia nutrition minerale de Ia plante-h6te, notamment Ia nutrition phosphatee (Harley, 1969 ;Sanders et Tinker, 1971 ;Bowen et a/., 1975: Callow et a/., 1978Walker et Powell, 1979 ;Cappacio et Callow, 1982 ;Strullu eta/., 1981a et b;Strullu eta/., 1982a et b).…”