Maize leave samples (2 mm3
) were fixed by immersion in 3% (v/v)
glutaraldehyde in 0.1 m sodium cacodylate buffer (pH 7.2) for 2 h at
room temperature and post-fixed with 1% (w/v) osmium tetroxide in
the same buffer for 1 h at 4°C. Samples were dehydrated in a
graded ethanol series and embedded in Epon 812 (JBEM
Chemicals Pointe-Claire, Quebec, Canada).