Flower Biology
Flowering occurs in plants with particular climatic changes such as sunny, cold, dry or drought conditions. In conducive growing conditions plant size and foliage increase, but many flowers are not produced.
Flowers are the reproductive organs of a plant. Sexual reproduction in plants is enabled by flowering and is a sign of plant survival. Some plants do not require reproduction by flowering but reproduce by sending out runners eg., strawberry, and form identical plants. This form of propagation is termed asexual reproduction.
Structure and function of flowers
The male gametes in flowers are the pollen, while ovules are the female gametes. Pollen from one plant fertilizes the ovules of another plant through flowers, in the cross-fertilisation method of reproduction.
A flower's male parts are the Stamens and female parts are the carpels. Though, most plants produce flowers that have both male and female reproductive parts, separate male and female flowers bloom in some plants.
Study the parts of a simple flower with reference to the location and function of the parts given in the following details. 
- Sepals
- Generally green colored exterior protective coverings of a flower.
- Petals
- Mostly colored to attract pollinating insects and are framed by sepals.
- Nectar
- The sweet liquid at the base of petals that attracts insects.
- Stamens
- Pollen producing male organs that include the anther and supporting filament.
- Carpels
- Female organs that produce ovules inside the ovary, which is attached to the style and stigma.
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Pollination and fertilisation In Flowers
The anther holds pollen. The anther swells when the pollen are ripe and splits open, releasing the pollen in response to sunny, dry conditions. The ovary is located at the base of the petals. Stigma is a sticky tip of a stalk-like style .
A long pollen tube grows from the pollen landing on the stigma down the style towards the ovule, which is located in the ovary. The ovule is fertilized by the male nucleus of the pollen after passing down the tube. Once fertilisation occurs, a fruit usually forms after the petals fall. A swollen ovary wall forms flesh of the fruit.
Insect Pollination and Wind Pollination
Many flowers with brightly colored petals and attractive chemical scents attract insects that act as agents of pollination.
Reproduction in plants without these features, such as significant flowers, is through wind-pollination. Wind-pollinated plants include grasses.
| Wind pollinated flower | Insect pollinated flower |
|---|---|
| Very small petals | Large colored petals |
| No scent | Scented |
| No nectar | Nectar |
| Many smooth pollen grains | Rough pollen that easily sticks to insects |
| Large anthers hang outside flower | Anthers and stigma found inside the flower petals so that visiting insects are touched |
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