Fruit and seed

The fruit is a feature found only in flowering plants. It is the mature, ripened ovary formed after fertilisation. A fruit formed without fertilisation is parthenocarpic.

A fruit has a wall, the pericarp, around its seeds. The pericarp can be dry or fleshy; a thick fleshy one is divided into outer epicarp, middle mesocarp and inner endocarp.

Drupe: a one-seeded fruit from a monocarpellary superior ovary, as in mango and coconut. Mango: thin epicarp, fleshy edible mesocarp, stony hard endocarp. Coconut: fibrous mesocarp.

Ovules become seeds after fertilisation. A seed is a seed coat around an embryo; the embryo has a radicle, an embryonal axis and one cotyledon (wheat, maize) or two (gram, pea).

Dicot seed coat: outer testa and inner tegmen. The hilum is the scar where the seed was attached to the fruit; the micropyle is a small pore just above the hilum.

Dicot embryo: an embryonal axis with the radicle at one end and the plumule at the other, plus two cotyledons, which are frequently fleshy stores of reserve food.

Endospermic seeds keep a food-storing endosperm formed by double fertilisation, as in castor. In bean, gram and pea the mature seed has no endosperm (non-endospermous).

Monocot seeds are generally endospermic; orchid seeds are an exception. In maize the membranous seed coat is fused with the fruit wall, and the bulky endosperm stores food.

The maize endosperm is covered by a proteinous aleurone layer. The small embryo lies in a groove at one end; it has one large shield-shaped cotyledon, the scutellum, and a short axis whose plumule is sheathed by the coleoptile and whose radicle is sheathed by the coleorhiza.