The pericarp surrounds the whole corn kernel, affecting the insect and pathogen invasion of the kernel and water penetration in the kernel. It may be 2-20 cells thick and is, genetically, female tissue. It is also without pigments.
Surrounding the starchy endosperm portion of the corn kernel, but within the pericarp is a single (usually) layer of cells known as the aleurone layer. These cells are part of the seed, the result of fusion of one nucleus from the pollen grain with two nuclei from the egg cell in the ovule. Whereas the cells in the rest of the endosperm function mostly to synthesize and accumulate starch, aleurone cells maintain more metabolic activity. Although only a single layer of cells, it can include 30% of the total proteins of the endosperm.
Anthocyanin production occurs within the aleurone cells, resulting in red and purple or blue corn kernels. Genes for lack of anthocyanin in the aleurone, allows the yellow color of starch endosperm cells carotenoid production to show in the common yellow corn kernels. Corn genetics for lack of carotenoid production in starchy endosperm, along with genes for no anthocyanin in aleurone, results in white corn kernels.
Aleurone metabolic activity contributes to much of the seed activity. Phytosterols infuse into the pericarp, contributing to insect and pathogen resistance. Although 80% of the oil in corn kernels is located in the embryo, 12% of the oil located in that thin layer of aleurone cells. Fibers from the aleurone cells and pericarp are processed together as corn bran, the aleurone contributing the oil to the bran animal feed.
The scutellum and aleurone cells are stimulated to produce amylase when moisture and temperatures are appropriate for germination. This enzyme assists in breaking down the starch of the endosperm, and thus making energy available for the growth of the embryo.
This layer of cells is an important component of both the use of corn grain and the growth of the next generation.
About Corn Journal
The purpose of this blog is to share perspectives of the biology of corn, its seed and diseases in a mix of technical and not so technical terms with all who are interested in this major crop. With more technical references to any of the topics easily available on the web with a search of key words, the blog will rarely cite references but will attempt to be accurate. Comments are welcome but will be screened before publishing. Comments and questions directed to the author by emails are encouraged.