Flowers lure insects and birds to plants using color, design and fragrance as bait. Once there, the visitors help pollinate seeds by transporting pollen from one plant to another. The seeds develop within the flower and have three primary parts: the embryo, endosperm and seed coat. After fertilized, a single seed may eventually grow into a new flowering plant.
The female part of the flower is the pistol, made up of the style, ovary and stigma. The ovules develop in the ovary. When an ovule matures, it becomes a seed. A flowering plant begins its life as an embryo, tucked inside a single flower seed. The embryo is composed of a stem, leaves and primary roots. Typically, the primary roots, or radicle, are the first part of the plant to begin growing. The part of the seed that develops into the first shoot with leaves is called the plumule.
The embryo, tucked inside the seed, needs nourishment to grow and mature. The endosperm typically provides this need. Endosperm is simple tissue made up of starches and proteins used to nourish the embryo. During germination, an enzyme is released, which causes the starch in the tissue to break down into sugar, which supplies food to the embryo.
The part of the plant that processes the food is the cotyledon. The number of cotyledons a flower seed has varies by plant type. In some plants, the cotyledon acts as food storage, absorbing the food tissue and distributing it to the growing embryo when necessary. According to Arizona Cooperative Extension Master Gardeners, the orchid is an exception, as it does not have endosperm as a built-in food supply.
Protecting the embryo is the outer covering of the seed called the seed coat. The tiny opening in the seed coat, where a pollen tube enters is the micropyle. This seed coat shields the embryo from insects, injury and the elements. Eventually, when the embryo matures and is ready to free itself from the confines of the shell, the coat will break open. Some flowers have very hard seed coats or shells, while other flowering seed coats might be thin and fragile.