Describe the structure of Megasporangium with a diagram

Explanation

The ovule is a small structure attaced to the placenta by means of a stalk called funicle. The body of the ovule fuses with funicle in the region called hilum. Thus hilum represents the junction between ovule and funicle. Each ovule has one or two protective envelopes called integuments. integuments encircle the nucellus except at the tip where a small opening called the micropyle is organised. opposite the micropylar end, is the chalaza representing the basal part of the ovule. Enclosed within the integruments is a mass of cells called the nucellus. Cells of the nucellus have abundant reserve food materials. Located in the nucellus is the embryo sac or female gametopyte. An ovule generally has a single embryo sac formed from a megaspore.

Megasporogenesi: The process of formation of megaspores from the megaspore mother cell is called megasporogenesis. Ovules generally differentiate a single Megaspore Mother Cell (MMC) in the micropylar region of the nucellus. It is a large cell containing dense cytoplasm and a prominant nucleus

The MMC undergoes meiotic division. Meiosis results in the production of four megaspores. The development of female gametophyte: In a majority of flowering plants, one of the megaspores is functional while the other three degenerate. Only the functional megaspore develops into the female gametophyte. This method of embryo sac formation from a single megaspore is termed as monosporic development