Megasporogenesis: Development and Types

Table of Contents

• Introduction
• Development
• Types of Embryo Sac Development

The process of development of megaspores from megaspore mother cells is known as megasporogenesis. The megaspores are developed in the female reproductive organs.

• A layer of sporogenous tissue is present in the ovules of the female flowering plant.
• The megaspore mother cells (MMC) are developed from the sporogenous tissue. It is a large diploid cell with a prominent nucleus and dense cytoplasm.
• The MMC undergoes meiotic nuclear divisions to produce four haploid megaspores.
• The megaspores are arranged axially, called the linear tetrad.
• Out of the four, only one megaspore is functional and the rest three degenerate.
• The megaspore at the chalazal end is functional, and the three towards micropyle degenerate.
• The one functional megaspore divides mitotically to form the embryo sac, a process called megagametogenesis.
• It divides multiple times to produce eight haploid nuclei for the embryo sac, which is also called a megagametophyte.

Read: Embryo Sac Development

1. Monosporic

In the majority of angiosperms, the embryo sac develops from one functional megaspore while the other three degenerate. For example, Oenothera, Polygonum.

2. Bisporic

In this type, two of the megaspores take part in embryo sac development. Examples are Allium, Scilla, and Trillium.

3. Tetrasporic

In this type, all four megaspores take part in embryo sac development. For example, Peperomia.

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Also, see:

• Megasporogenesis vs Microsporogenesis
• Diagram of Embryo Sac