Structure of Maize Grain

 Structure of Maize Grain

The Maize grain can be taken as an example of monocotyledon seed.

The maize grain is a small one-seeded fruit called the caryopsis. In maize grain the seed coat (testa) is fused with the fruit wall (pericarp). Externally, the maize grain is yellow in colour and somewhat triangular in shape. On one side of the grain is a small, opaque, oval and whitish area in which embryo lies embedded. A longitudinal section of the seed shows the following structures:

1. Seed coat: It is formed of a thin layer surrounding the whole grain. This layer is made up of seed-coat and pericarp, i.e. fruit wall.

2. Endosperm: When internally examined, maize grain is found consisting of two unequal portions divided by a layer called epithelium. The bigger portion, the endosperm which is yellowish or whitish is the food storage tissue of the grain and is rich in starch. But its outermost layer contains only protein and is called aleurone layer. On the other side of the endosperm towards the pointed end lies an opaque body called embryo.

3. Embryo: It consists of one large and shield shaped cotyledon. This is also known as scutellum in the case of maize and other cereals. The axis of the embryo lies embedded in the scutellum. The axis consists of a plumule at the upper portion and the radicle at the lower end. Both radicle and plumule are enclosed in sheath. The sheath covering the plumule is known as coleoptile and that covering the radicle is known as coleorhiza. The cone-shaped coleoptile has a pore at the apex through which the first foilage leaf emerges during germination.