- It is a ripened ovary developed after fertilisation.
- It is a characteristic feature of the flowering plants.
- A fruit formed without fertilisation of the ovary is called parthenocarpic fruit.
- In mango & coconut, fruit is called a drupe. They are one seeded and develop from monocarpellary superior ovaries.
- A fruit consists of
o Pericarp (fruit wall): It may be dry or fleshy.
Thick and fleshy pericarp is differentiated into outer epicarp, middle mesocarp and inner endocarp.
- In mango, the pericarp is well differentiated into thin epicarp, fleshy edible mesocarp and stony hard endocarp.
- In coconut, the mesocarp is fibrous.
- It is the mature ovule developed after fertilisation.
- A seed is made up of a seed coat and an embryo.
- Embryo is made up of a radicle, an embryonal axis and one (e.g. wheat, maize) or 2 cotyledons (e.g. gram & pea).
Structure of a Dicotyledonous Seed
- The outermost covering of a seed is the seed coat.
- Seed coat has 2 layers: outer testa and inner tegmen.
- On the seed coat, there is a scar called hilum through which the developing seeds are attached to the fruit.
- Above the hilum is a small pore called the micropyle.
- Within the seed coat is the embryo, consisting of an embryonal axis and two cotyledons.
- The cotyledons are often fleshy and full of reserve food materials. At the two ends of the embryonal axis, the radicle and plumule are present.
- In some seeds such as castor, the endosperm is formed due to double fertilisation. It is a food storing tissue.
- In plants such as bean, gram and pea, the seeds are non-endospermous (endosperm is not seen in mature seeds).
Structure of Monocotyledonous Seed
- Generally, monocot seeds are endospermic but some are non-endospermic (e.g. orchids).
- In cereals such as maize, the seed coat is membranous and generally fused with the fruit wall.
- The endosperm is bulky and stores food.
- The outer covering of endosperm separates the embryo by a protein layer called aleurone layer.
- The embryo is small and situated in a groove at one end of the endosperm. It consists of one large and shield shaped cotyledon known as scutellum and a short axis with a plumule and a radicle.
- The plumule is protected in a sheath called coleoptile and radicle is protected in a sheath called coleorhiza.