Question

Explain the structure of megasporangium.

Answer 1

Ovule is connected to the placenta by means of a funicle. The hilum is the point of attachment between ovule and funicle. Each ovule is covered by a protective covering called integuments which surround the nucellus. At the tip, the integuments are absent leaving a small opening called the micropyle. The chalaza is present opposite to the micropylar end and forms the basal part of the ovule. Nucellus is the main body of the ovule made up of parenchymatous mass. The embryo sac also called female gametophyte is present inside the nucellus. The diploid megaspore mother cell undergoes meiosis to form 4 haploid megaspores by the process of megasporogenesis. Three out of four megaspores degenerate and only one is functional. The functional megaspore develops into the female gametophyte. It is a 7 celled and 8 nucleated structure consisting of two synergids, three antipodal cells, two polar nuclei and 1 egg cell.