First ten days

Pollination was successful and hormones in the new growing points of pollinated ovules begin the process of moving sugars to each new embryo.  Shortage of energy movement during the first 10 days is critical.  Plant stresses that cut off this movement, having a change in balance of hormones for each kernel.

​Two major hormones in corn are cytokinins and auxins.  Cytokinins affect cell division and auxins affect cell elongation.  Cytokinins are produced primarily in root tip meristems and transported via xylem to other meristems such as those developing in each pollinated ovule.  As these embryo meristem cells divide, the attraction of cytokinins increases.  Concentration of cytokinins in these meristems also affects translocation of glucose molecules to each developing embryo, as this carbohydrate moves through the phloem from leaves and stem pith tissue to the new cells.  Excessive stress affecting water for xylem transport, or, reducing sugar production can reduce the constant flow of cytokinins to developing kernels.  If this occurs during the first 10 days after pollination, another hormone, abscisic acid (ABA) accumulates at the base of the ovule.  This hormone causes development of thick-walled cells, blocking transport of cytokinins and sugar into the kernel.  As a result, the kernel does not develop further. 
 
Genetics and environment have a great effect on the balance of hormones during corn grain development.