Nucleolar Number at Premeiotic and Mitotic Interphase in Maize

Abstract

Premeiotic and somatic interphase cells from inbred KYS of maize were scored for number of nucleoli. Dual nucleoli occurred in 32 of 508 cells in the meristematic region of root tips, but only one of 520 cells at premeiotic interphase had two nucleoli. All other cells had a single nucleolus. The occurrence of cells with two large nucleoli filling most of the nuclear space and cells with nucleoli at opposite nuclear boundaries disclosed that dual nucleoli were the result of widespread separation of organizers rather than inhibition of fusion due to a paucity of nucleolar material. A single nucleolus was attributed to proximity of organizers and nucleolar fusion. The presence of a single nucleolus in all but one exceptional cell at premeiotic interphase suggests convergence, preparatory to synapsis, of the two homologues of chromosome 6 during the mitosis preceding meiosis.