Caryopsis - Development of Fruit

In cereals each carpel has one ovule and therefore the mature fruit has, just one seed. During maturation, very little or no cell divisions are necessary in the ovary wall. The pericarp and the remains of the integuments of the seed get completely fused. In wheat caryopsis three main regions can be distinguished:

1. The caryopsis wall which includes the pericarp, seed coat and remains of nucellus;
2. Endosperm;
3. Embryo.

The pericarp can be distinguished into five layers:

1. Epidermis;
2. Hypodermis;
3. Zone of thin-walled cells;
4. Cross cells;
5. Tube cells.

The outer epidermis and hypodermis together form the exocarp, having thick-walled compressed cells. Inside the exocarp are one or a few layers of thin-walled parenchymatous cells. These are followed by the cross cells that have thick walls with characteristic pits elongated transversely to the cell. The tube cells constitute the inner epidermis of the pericarp. These cells have thinner walls than cross cells but these too are pitted. In the mature caryopsis testa is destroyed but tegmen is discernible along with one or two layers of nucellus.