Maize grain. Light micrograph of a vertical section through the grain of a maize plant (Zea mays). This is the fruit of the plant, and includes the endosperm (larger area, upper right, light pink), which is full of food in the form of starch grains and protein crystals. The seed (smaller area at lower left, dark pink) contains the embryo. The embryonic area includes a plumule and radicle enclosed within the coleoptile and coleorhiza respectively (white areas). The plumule and radicle are the structures by which the seed will germinate and develop a root and leaf system, developing into a new plant. The endosperm provides nutrients for the germinating plant. Maize is a crop that is cultivated for its grains, which are a rich source of starch.