Cytochemical and ultrastructural studies on normal and segregated nucleoli in meristematic cells

The location of the two nucleolar components, in meristematic root tip cells ofAllium cepa has been studied. The “segregation” of granular and fibrous components of the nucleoli was induced by adenosine-3′deoxyriboside. The relationship between the ultrastructure and the stain affinities of both nucleolar regions has been determined by using different selective nucleolar stains. The “pars fibrosa” appears positive in the silver, lead, zinc, and methylen blue stains and shows a high ATPase activity