plant surface microbiology.pdf

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13 Root Surface in Ectomycorrhizas 215
rccw
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a b
*
rhcw
c d
Fig. 3. a, b Suberized (arrows) root cap cell layers close to the root apex of Picea abies.
The outer layers detaching (*) and partly decomposed. Cell wall or vacuolar, phenolic
residues form the superficial layer. Scale 0.5 mm. c Superficial layer on short root cortical
cell formed by the suberized root cap cell wall lined by phenolic residues (arrow). Scale
0.3 mm. d Cell wall of root hair with no suberin layer (scale 0.3 mm). cc Cortical cell, ccw
cortical cell wall, ph phenolic residues, rccw root cap cell wall, rhcw root hair cell wall
amounts of phenolic residues (Fig. 2 c). An attempt was undertaken to clarify
the situation by carefully studying the cell layers (Fig. 3a, b). Additional hints
for recognition of cell wall material were obtained by immunogold labelling
(see below). At the final stage of root development, when only the innermost
root cap cell wall and its suberin layer are preserved on the root cortical cell
wall (Fig. 3 c), the thin, electron-dense layer on top of the suberin layer can
only be interpreted as the phenolic residues of the former vacuole. Dehydration
of mycorrhizas in alcohol and embedding in LRWhite resin may obscure
the suberin layer (Kottke 1997; Bonfante et al. 1998), but high pressure cryofixation,
dehydration by acetone and embedding in Araldite/Epon or embed-