Pre-fertilisation — Part 1: Microsporogenesis and megasporogenesis: visual lesson, ISC Class 12 Biology

Lesson

Sexual Reproduction in Flowering Plants: Pre-fertilisation

Part 1 — how the male and female gametophytes are formed inside the flower.

In this lesson you will

Draw and label the T.S. of a mature anther and a two-celled pollen grain
Describe microsporogenesis and the development of the pollen grain
Draw and label the L.S. of an anatropous ovule
Describe megasporogenesis and the development of a seven-celled, eight-nucleate embryo sac

Concept

The two reproductive whorls

A stamen has a slender filament and a terminal anther. A typical angiosperm anther is bilobed and dithecous: each lobe has two thecae, so the anther holds four microsporangia. The pistil has stigma, style and ovary; the ovary contains ovules attached to the placenta.

Table of the male and female whorls with their parts
Whorl	Unit	Parts
Androecium	Stamen	Filament, anther (four microsporangia)
Gynoecium	Pistil (carpel)	Stigma, style, ovary with ovules on the placenta

Diagram

Transverse section of the anther

In T.S. the anther is tetragonal. Each microsporangium is surrounded by four wall layers: epidermis, endothecium, middle layers and tapetum. The centre holds sporogenous tissue.

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