Sexual Reproduction in Flowering Plants

Lesson

Part 1 — inside the stamen and the pistil: how a flower makes its male and female gametophytes before pollination.

In this lesson you will

Describe the structure of the stamen, anther and microsporangium
Explain microsporogenesis and the structure of a pollen grain
Describe the pistil and the parts of an ovule
Explain megasporogenesis and the development of the embryo sac

Concept

The flower: events before fertilisation

Long before a flower opens, its fate is decided by hormonal and structural changes that turn a shoot apex into a floral bud. Inside the bud, the androecium (whorl of stamens) and the gynoecium (pistils) develop.

Table comparing the male and female sides of a flower: whorl, spore-forming organ, mother cell, gametophyte and gametes
	Male side	Female side
Whorl	Androecium (stamens)	Gynoecium (pistils)
Spore-forming organ	Microsporangium in the anther	Megasporangium (ovule) in the ovary
Mother cell	Microspore mother cell	Megaspore mother cell
Gametophyte	Pollen grain	Embryo sac
Gametes	Two male gametes	One egg cell

Diagram

Stamen and anther

A stamen has a long filament and a terminal, usually bilobed anther. Each lobe has two thecae, so a typical anther is dithecous and holds four microsporangia at its corners. The microsporangia later become pollen sacs.

Cookies