Worlds of David Darling
Encyclopedia of Science
Home > Encyclopedia of Science


types of seed
Representative types of seed: side and sectioned views: (a) Winged endospermic seed of pine (Pine); (b) endospermic castor oil seed (Ricinus communis; (c) non-endospermic broad bean seed (Vicia faba); (d) endospermic "seed" of corn (maize; Zea mays) (botanically this is really a fruit but the fruit wall is thin and fused to the seed coat); (e) endospermic seed of the onion (Allium cepa)
Section of the seed of mono- and dicotyledon
The mature reproductive body of angiosperms and gymnosperms. Seeds also represents a resting stage which enables plants to survive through unfavorable conditions. The germination period varies widely from plant to plant.

Seeds develop from the fertilized ovule. Every seed is made up three main parts:
  • Embryo. This is the essential living part of the seed. It consists of a radicle, which gives rise to the root, and a plumule, the growing part of a young shoot; the part containing these two is called the hypocotyl. One or two seed leaves, or cotyledons, grow out from the hypocotyl and may or may not be taken above the ground during germination. Plants that produce one seed leaf are called monocotyledons and those that produce two, dicotyledons. The cotyledons may function, after germination, as leaves, or they may (in seeds like the bean) contain the food-store.

  • Food-store. This is the reserve of food on which supplies the embryo and growing plant until it is able to make its own food. The food-store may be in the cotyledons or in a part of the seed called the endosperm. It is this stored food which is of nutritional value (see nutrition) to humans and other animals.

  • Testa or seed-coat. This the tough protective outer covering the seed. It often has outgrowths which help in dispersal of the seed.
Flowering plants produce their seeds inside a fruit, but the seeds of conifers like naked on the scales of the cone. Distribution of seeds is usually by wind, animals or water and the form of seeds is often adapted to a specific means of dispersal.

Related category