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 2 times 100) for 20 min each ; following by infiltration and embedding in Spurr’s low viscosity epoxy resin