Grades 6–8 · Organisms
How does pollen reach the place a seed can begin?
A bee leaving a flower may carry the beginning of a future seed as a dusting of pollen. When pollen moves from an anther to a stigma, pollination has occurred. This is a delivery step: it brings the cells that supply sperm to a receiving surface, but a seed has not yet formed.
The anthers are the flower parts that produce pollen. A bee gathering food can brush against an anther, pick up grains and leave some on another flower's stigma. Wind carries pollen in other plant species. Neither the bee nor the wind needs to plan a seed's formation; the flower's structures make this transfer possible during ordinary movement.
Compatible pollen on a stigma can germinate and grow a pollen tube. The tube passes through the style, the connection between the stigma and the flower's ovary. Inside the ovary are ovules, structures that can develop into seeds. The tube provides a route for sperm to reach an egg cell within an ovule. Pollen arriving outside the flower has therefore established a connection to reproductive cells sheltered inside it.
The bee links the Anther of Flower A with the Stigma of Flower B. The Close-up places the Ovule farther along the possible pollen-tube route, beyond the initial transfer.
In the diagramPollination: pollen reaches a stigmaAntherStigmaBee carries pollenClose-upOvuleFlower AFlower BTransfer happens before possible fertilization.
A sperm can join the egg in fertilization, forming a new cell that develops into the plant embryo. The ovule can then develop into a seed containing that embryo. Pollination delivers; fertilization joins reproductive cells; development produces the seed. Not every pollen grain completes that journey, but a successful transfer can help turn a brief flower visit into a new generation of plants.
About this explanation
Starting knowledge: Identify flower structures and distinguish pollination from fertilization.
Sources
- OpenStax Biology 2e — Pollination and Fertilization