Question

Describe the structure of maize grain.

Answer 1

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 with the following structures:

• 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.
  
• Endosperm: Maize grain consists 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.
  
• 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 is 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 a sheath called coleoptile and that covering the radicle are known as coleorhiza.