Year 1 · Reproduction in plants and animals · Section 6.1
Flowers
A flower
A flower is a plant organ involved in reproduction. Its parts have different functions. A typical flower has a calyx, a corolla, and reproductive structures in the centre: stamens and a pistil.
Calyx and sepals
The calyx consists of sepals, which are usually green. They protect the flower bud from damage, drying out and cold. The sepals may be separate or joined together.
Corolla and petals
The corolla consists of petals, often large and brightly coloured to attract pollinating insects. In wind-pollinated plants, such as grasses, these parts are often small, reduced or inconspicuous. Petals may be separate or fused.
Insects such as bees can transfer pollen between flowers. This helps make fertilisation and seed formation possible.
Flower structure and function
Flowers can look very different, but many share the same basic structures. Stamens are the male reproductive organs, while the pistil is the female reproductive organ. Not every flower contains both.
Stamens
A stamen consists of a filament supporting an anther. Inside the anther are pollen sacs, where pollen grains form. When the anther opens, pollen is released.
Pollen grains carry the cells that produce the male sex cells. A pollen grain is not itself the same thing as a single male sex cell.
The pistil
A pistil consists of a stigma, style and ovary. The ovary contains one or more ovules, in which egg cells, the female sex cells, develop.
Fertilisation involves the fusion of a male sex-cell nucleus with an egg-cell nucleus. After fertilisation, ovules can develop into seeds and the ovary usually develops into a fruit containing the seeds.
Glossary
- Calyx
- The sepals together, protecting a flower while it is in bud.
- Corolla
- The petals together, often conspicuous and involved in attracting pollinators.
- Egg cell
- A female sex cell developing inside an ovule.
- Filament
- The stalk supporting the anther of a stamen.
- Pollen sacs
- Spaces within an anther in which pollen develops.
- Anther
- The pollen-producing upper part of a stamen.
- Sepals
- Usually green structures forming the calyx and protecting the bud.
- Petals
- Often colourful structures attracting pollinators; they may be separate or fused.
- Stamens
- The male reproductive organs of a flower that produce pollen.
- Pistil
- The female reproductive organ of a flower, containing the stigma, style and ovary.
- Stigma
- The surface of the pistil that receives pollen.
- Style
- The part connecting the stigma to the ovary.
- Pollen grains
- Small structures formed in the anther that carry cells involved in producing male sex cells.
- Ovary
- The lower part of the pistil containing one or more ovules.
- Ovules
- Structures within the ovary where egg cells develop and seeds can form after fertilisation.
Frequently asked questions
Which part of a flower produces pollen?
Pollen develops in pollen sacs within the anther. The anther and filament together form a stamen.
What does the calyx do?
The calyx protects the flower while it is in bud, for example against drying out and cold.
What are the parts of a pistil?
The stigma, style and ovary. The style connects the stigma to the ovary.