Formation of Seed and Fruit

After double fertilisation in angiosperms, the flower undergoes a series of coordinated changes that convert the reproductive structures into seed-bearing fruits. These changes represent the shift from a reproductive phase to a developmental phase in the plant's life cycle.

The two key simultaneous transformations are:

• Ovule → Seed (the fertilised ovule matures into a seed)
• Ovary → Fruit (the ovary wall ripens into the fruit wall)

A seed is a mature, fertilised ovule that contains an embryo enclosed within a protective outer covering (seed coat), along with a food reserve (endosperm or cotyledons).

A seed is the basic unit of reproduction and dispersal in flowering plants.

Structure of a Typical Seed:

A fruit is the mature, ripened ovary of a flower, usually formed after fertilisation. The ovary wall develops into the pericarp (fruit wall).

Structure of the Pericarp:

In fleshy fruits, the pericarp differentiates into three distinct layers:

1. Epicarp → Outermost layer (skin of fruit)
2. Mesocarp → Middle layer (often fleshy/edible)
3. Endocarp → Innermost layer (may be hard/papery)

Significance of Seeds

Significance of Fruits

• After double fertilisation, the flower shifts to a developmental phase: the ovule matures into a seed, and the ovary ripens into a fruit.
• A seed is a mature, fertilised ovule with an embryo enclosed in a protective seed coat and a food reserve (endosperm or cotyledons).
• The seed coat has a tough outer testa and a thin inner tegmen, both from the ovule's integuments.
• A typical seed also has the embryo (radicle, plumule, cotyledons), endosperm (3n food reserve), a micropyle for water and oxygen entry, and a hilum marking attachment.
• Albuminous seeds retain the endosperm for food storage, as in wheat, maize, castor, and coconut.
• Non-albuminous seeds absorb the endosperm fully and store food in cotyledons, as in pea, bean, and groundnut.
• A fruit is the ripened ovary; in fleshy fruits, the pericarp has three layers - epicarp (skin), mesocarp (fleshy/edible), and endocarp (hard or papery).
• Seeds protect and nourish the embryo and allow dormancy, dispersal, and genetic variation.
• Fruits protect and disperse seeds, store nutrients, and have commercial value as food and raw materials.