Root fragments were fixed by immersion in 3% (v/v)glutaraldehyde in 0.1 M pH 7.2 cacodylate buffer for 12 h at room temperature. After washing in cacodylate buffer three times (1 h each), samples were post fixed for 2 h at room temperature in darkness in 1% OsO4 prepared in cacodylate buffer. The samples were dehydrated through a graded ethanol series (70,95 and 2times 100) for 20 min each; following by infiltration and embed-
ding in Spurr’s low viscosity epoxy resin