seed

The germination of a corn grain. The plumule and radicle emerge from the seed coat and begin to grow into a new plant. The coleoptile protects the emerging bud and the first leaves.

The structure of seeds. The castor is a dicotyledon, a plant in which the developing plant has two leaves, developed from the cotyledon. In maize, a monocotyledon, there is a single leaf developed from the scutellum.

A bur entangled in a fox's fur. By the time the animal grooms itself and discards the bur it will probably have transported it some distance. A number of plants, including the burdock (shown here), disperse their seeds in this way.

A coconut begins to germinate after washing up on a beach. The outer husk of the coconut is very buoyant and seeds can be dispersed hundreds of kilometres by water.

The seeds of the sycamore are dispersed by wind.

Blackberry seeds are dispersed by the birds and animals that feed on the berries. Here a blackbird eats a berry. By the time the seeds have worked through the bird's digestive system it is likely that it will have moved some distance away from the original plant.

Reproductive structure of higher plants (angiosperms and gymnosperms). It develops from a fertilized ovule and consists of an embryo and a food store, surrounded and protected by an outer seed coat, called the testa. The food store is contained either in a specialized nutritive tissue, the endosperm, or in the cotyledons of the embryo itself. In angiosperms the seed is enclosed within a fruit, whereas in gymnosperms it is usually naked and unprotected, once shed from the female cone.

Following germination the seed develops into a new plant.

Seeds may be dispersed from the parent plant in a number of different ways. Agents of dispersal include animals, as with burs and fleshy edible fruits, and wind, where the seed or fruit may be winged or plumed. Water can disperse seeds or fruits that float, and various mechanical devices may eject seeds from the fruit, as in the pods of some leguminous plants (see legume).

There may be a delay in the germination of some seeds to ensure that growth occurs under favourable conditions (see after-ripening, dormancy). Most seeds remain viable for at least 15 years if dried to about 5% water and kept at −20°C/−4°F, although 20% of them will not survive this process.