Pericarp and aleurone of corn kernels

​Outermost covering of a corn kernel is the pericarp, a part of the female plant similar to the outer covering of any fruit.  Its genetics is that of the female plant.  It can range from 2 to 20 cell layers thick, mostly depending on the genetics of the variety.  Immediately inside and basically fused to the pericarp is a very thin wall of the actual seed coat.  These tissues surround the whole kernel, including the embryo and the endosperm.  Endosperm is mostly composed of large cells with stored starch molecules but surrounded by a few layers of living specialized cells, higher in proteins called the aleurone layer.  These cells’ activities become dormant as abscisic acid increases with seed maturity.  When exposed to moisture, the embryo produces gibberellic acid, causing activity in the aleurone cells to produce the enzyme amylase.  This enzyme migrates into the starchy endosperm cells, breaking down the starch into glucose molecules for use in the embryo growth metabolism.
 
Pericarp and aleurone layers become important contributors to insect and pathogen resistance.  They are also the location of major pigments affecting the color of the grain and are the main components of corn bran with the aleurone layer and the embryo as the main source of protein in corn grain.