Corn seed aging evaluation
Among the challenges facing seed producers and their customers is predicting the effective germination of the seed in the field. Dormant seed remains alive, maintaining the membranes of the many cell organelles at a low rate. Membrane integrity is essential to the increased metabolism needed for germination. Physical and time factors in the journey from when the corn seed is forming in the field, through storage at the grower’s farm all can have some effect on the eventual uniform emergence in the field the following spring. Predicting the final germination, the slope of aging in the seed after harvest is the effort of seed testing.
Standard warm tests are done at 70°F in a uniformly moist substrate. Cold tests are usually performed with a week at 50° and then 4-7 days at 70°. The warm test basically identifies the individual seed that have deteriorated beyond repair even at a temperature that would allow normal recovery of damage whereas the low temperature of the cold test inhibits the metabolism needed to repair the membranes as they swell from water imbibition. Often seed producers test seed immediately after drying and shelling and then later after adding treatment and bagging. Tests done at these two times can allow an estimation slope in which the seed is aging or deteriorating (Seed Testing info).
A few factors become critical in correctly predicting the germination percentage at the time of planting the next spring. Sampling to represent the units of a lot that are sold is a potential problem that is usually met automatically by seed producers but still requires care. A more difficult problem comes when an environmental interaction in the production field causes cellular stress that don’t show until a few months before the seed is planted the following spring. Seed producers are faced with the difficult problem of timely distribution of the seed in a relatively short time and yet potentially testing the seed a few months before it is planted in the field. Genetics also seem to add to the problem as some female parent genetics tend to deteriorate quicker than others.
Adding to the confusion, each germination lab has slight differences in results, even if all attempt to follow nearly the same methodology. Slight differences in defining the slower germinating seed contributes to part of the problem but also even attempts to have identical methods seem to be difficult. Ideally a lab attempts to be consistent and a seed producer attempts to adapt their in-house decisions on marketing seed lots with some field data comparisons with germinations. Even then, the field studies need multiple reps because of usual field soil variabilities.
Ever notice that despite our desire for things to be simple, it rarely happens that way?
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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.