Preserving seed viability

t​Each seed to be planted next year will have a full set of the hybrid genes located in each cell of the embryo.  Natural drying of seed in the field allows a temporary delay in cellular activity in corn seed about 40 days after pollination. Respiration and other metabolism in the embryo cells slow, preventing germination.  Preservation of seed viability for the next season requires continuation of the seed drying to 14-7% to prevent faster metabolism.  Corn seed producers control this drying process, carefully avoiding higher temperatures that could destroy the cellular physiology but yet quickly dry the harvested seed.  This is mostly done by using fans to remove the released moisture from environment surrounding the seed. 
 
Drying speed is significant because moisture levels between 32% and 15% allow some degradation of cellular membranes but without the adequate replacement that occurs in actively growing plants.  This ageing process shortens the eventual viability of the seed.
 
Multiple studies have shown that seed respiration rates are affected by storage conditions and that these eventually affect germination percentage and seedling growth rate. Genetics also enter into these factors.  Pericarp wall density affects the ease of moisture movement into the embryo.  Some corn genotypes are more vulnerable to uptake of atmospheric moisture than others.  Pericarp tissue is part of the female parent of the corn kernel and therefore vulnerability to seed germination deterioration due to moisture during storage is often associated with the hybrid female parent.  Two inbreds may combine to give identical hybrid parent characteristics, but one of the inbreds may be superior for germination preservation when used as the female parent.
 
Successful preservation of high germination rates in the spring are dependent on multiple factors including stresses during seed development, drying conditions and genetics of parent seed.