Aleurone

The aleurone is a cellular layer of the seed endosperm found in many cereal grains, such as wheat, barley, maize, and oats. It consists of living, often relatively large and metabolically active cells that lie just inside the seed’s outer layers (the bran) surrounding the starchy endosperm. The aleurone is rich in proteins, lipids, minerals, and enzymes, and it plays a key role in seed nutrition and germination.

In most cereals, the aleurone is a distinct outer layer of the endosperm, typically only one cell thick, though some species have several aleurone cell layers. During kernel development, these cells accumulate nutrients and enzyme precursors and remain viable after seed maturation. The aleurone layer is often associated with a high content of storage compounds and with enzymes that are mobilized during germination.

During germination, gibberellins produced by the embryo diffuse to the aleurone layer and induce the synthesis and secretion of hydrolytic enzymes, including alpha-amylases and proteases, into the surrounding endosperm. These enzymes break down starch and stored proteins, releasing sugars and amino acids that feed the growing embryo. This process is a primary mechanism by which the seed converts stored reserves into usable nutrients.

The aleurone layer has practical significance for milling and nutrition. It contributes to the bran fraction and to micronutrient content, so its removal during refining reduces dietary fiber and minerals. In research, aleurone tissue is used to study hormonal signaling and enzyme induction during germination.