1989/11/01 by Sandra K. Law, Edward C. Yeung · 2 citations
Biochemistry, Genetics and Molecular Biology · #Biology #Botany #Callose #Cell #Cell biology #Cell division #Cell wall #Embryo #Genetics #Megaspore #Meiocyte #Meiosis #Ovule #Plant Reproductive Biology #Primordium
paper · doi:10.1002/j.1537-2197.1989.tb15151.x
openalex publication_date 1989/11/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/25
Calypso bulbosa is a terrestrial orchid that grows in north temperate regions. Like many orchids, the Calypso has ovules that are not fully developed at anthesis. After pollination, the ovule primordia divide several times to produce a nucellar filament which consists of five to six cells. The subterminal cell of the nucellar filament enlarges to become the archesporial cell. Through further enlargement and elongation, the archesporial cell becomes the megasporocyte. An unequal dyad results from the first meiotic division. A triad of one active chalazal megaspore and two inactive micropylar megaspores are the end products of meiotic division. Callose is present in the cell wall of the megaspore destined to degenerate. In the mature embryo sac the number of nuclei is reduced to six when the chalazal nuclei fail to divide after the first mitotic division. The chalazal nuclei join the polar nucleus and the male nucleus near the center of the embryo sac subsequent to fertilization.