Corn kernel pericarp
The kernel is a fruit, the female plant’s ovule outer wall retained as the pericarp. Therefore, the genetics of the pericarp is totally inherited from the female plant. Although the layer surrounding the seed ranges from only a few cells to several cells deep, it has several major contributions to the success of the seed.
Cell walls of the pericarp are thick and tightly held together when the kernel is mature, forming a barrier to the multiple insect and pathogen pests. Genotypes vary in number of cell layers in the pericarp. Moisture loss after black layer is an evaporation processes in which seed moisture must pass through the pericarp, with faster drying linked with thinner pericarps (and loose husk leaves). Thinner pericarp is associated with better digestibility in sweet corn but may be associated with poorer germinating sweet corn. Thicker pericarp is associated with better microwavable popcorn. A thick pericarp has been hypothesized to slow down imbibition during germination resulting in less damage although other factors complicate conclusions. It is probable that pericarp composition has some effect on germination whether from reducing pest damage or imbibition speed. Regardless, the pericarp, essentially a fruit outer wall does have positive and negative effects on our desirable use of the corn kernel.
Pericarp cells in mature kernels are metabolically dead. The lignin of the cell walls is linked to potentially active compounds like phenols that can inhibit fungi such as Fusarium species. Although the genetics of the cells, when alive, was that of the female plant, the layer of cells inside the pericarp is the metabolically-active aleurone. These cells are an actual part of the seed and therefore controlled by the genetics of cross of the male and female plants. Among the products of the aleurone cells are phenols and other compounds for resistance to fungi. These probably move into the pericarp as well. Although the two types of cells can be separated it is probable that proximity can lead to confusion in understanding all of pericarp function.
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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.