WHAT IS A SEED?
Each and every seed is a miracle of biological engineering. Weighing anywhere from 1/35000000 (one 35 millionth) of an ounce for an orchid seed, and up to as much as 18 kg for the enormous Coco de Mer seed, all living seeds contain the complete genetic blue print of its parents which they can use to replicate themselves to a similar design.
I suppose that strictly speaking, a seed is a small embryonic plant enclosed within its seed coat, together with a repository of stored food in the form of carbohydrates. The seed itself is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant. The formation of the seed completes the process of reproduction in seed bearing plants (started with the development of flowers and pollination), with the embryo developed from the zygote and the seed coat from the integuments of the ovule.
1. An embryo
2. A supply of energy and nutrients for the embryo
3. A seed coat.
The embryo is the immature plant from which a new plant will grow provided that suitable conditions are available. The embryo will produce a single leaf (known as the cotyledon) in monocotyledons, or two leaves in almost all dicotyledons. Gymnosperms will produce two or more leaves.
The radicle is the name for the embryonic root, while the plumule is the name for the embryonic shoot. The embryonic stem above the point of attachment of the cotyledon or cotyledons is the epicotyl. The embryonic stem below the point of attachment is the hypocotyl.
Along with the embyo, and found within the seed coat, is a store of nutrients and carbohydrates. for the seedling that will grow from the embryo. The form of the stored nutrition varies depending on the kind of plant. In angiosperms, the stored food begins as a tissue called the endosperm, which is derived from the parent plant via double fertilization. The usually triploid endosperm is rich in oil or starch and protein.
In addition to the three basic seed parts, some seeds have an appendage on the seed coat such an aril (as in yew and nutmeg) or an elaiosome (as in Corydalis) or hairs (as in cotton). There may also be a scar on the seed coat, called the hilum; it is where the seed was attached to the ovary wall by the funiculus.