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Morphological and physiological evidences for the
involvement of the root-cap in ectomycorrhiza formation
between Eucalyptus globulus and Pisolithus
tinctorius.
poster presentation of the Forest Biology
Laboratory
AZEMAR-LORENTZ STEPHANIE, MICHEL CHALOT, BERNARD BOTTON &
JEAN DEXHEIMER
University Henri Poincarè-Nancy I, Faculty of
Sciences, Laboratory of Forest Biology, U.A. INRA 977, BP
239, F-54500 Vandoeuvre Cedex, France
ICOM1 Abstract
Observations on the root-cap anatomy in ectomycorrhizas,
autohistoradiography techniques and capillary zone
electrophoresis (CZE) applied to soluble carbohydrate
determinations have shown a particular relationship
between the host plant (Eucalyptus globulus) and the
mycorrhizal fungus (Pisolithus tinctorius). In the
functionnal part of the mycorrhiza (biotrophic area), the
interactions between the plant and the fungus induced
morphological changes in both partners of the symbiosis in
order to facilitate the mutual exchanges. In contrast, the
root-cap behaviour was completely different :
morphological changes appeared only in the plant parts
whereas the fungus was not affected. However, the fungus
benefited of the nutrient supply resulting from a
significant degradation of the cell walls (visualised by
PATAg Test in M.E.T and detection of galactose in CZE),
from depolymerisation of mucilage (PATAg Test and
detection of fucose in CZE) and from degradation of
phenolic compounds (M.E.T). Autohistoradiography showed a
transfer of [3H]glutamate from the fungus to
the host plant with an accumulation in the meristematic
zone. These results suggest that the root-cap is not a
biotrophic area but rather a saprophytic zone which may be
involved in the achievement of the mycorrhizal process.