Corn seed ages, like all of us, but not every seed within a seed lot nor every seed lot of a hybrid nor every hybrid age at the same rate. These principles are well known but the seed industry still has battles to manage this natural process. Most of the ageing process is believed to be occurring at the membrane level where the metabolism activity is occurring even at a low level when seed is dried below 13.5% moisture. Membranes of major cell organelles responsible for respiration also need some upkeep to retain function. Environment in the field and later in the seed processing plant can affect the integrity of the membranes in the seed prior to drying. It is established that most modern genotypes benefit from rapid drying from air movement rather than high temperatures, but outside environments can influence meeting that goal.
Most seed are dried to 11-12% moisture, providing some leeway for individual seed differences within a seed lot. Long term storage of seedstock parent seed is sometimes dried to 7-8%, without notable drops in germination for a few years. Adding slight amounts of moisture, not enough for germination but enough to accelerate cellular respiration, can lead to a drop in germination percentage. I have not found research studies on this subject, but 3 personal examples come to mind. I witnessed a company retreating carryover seed with intent of maintaining the germination quality, but the result was a drop of germination. Perhaps it was from handling damage or perhaps from moisture addition. Another case that I had witnessed was when a company in a humid environment added a seed treatment that resulted adding some moisture to the seed but did not dry the seed immediately, resulting in a lower germination.
Several years ago, a seed company wanted to test our ability to distinguish ‘selfed’ seed from hybrid seed, by adding colored seed treatment to cover up the different seed colors originally on the female parent seed from the hybrid seed. We reported the selfs but also a low germination. After discussion, the customer sent us the original seed without the extra seed treatment, and we found a higher germination. Some seed treatment components can be damaging to seed but adding a small amount of moisture from the seed treatment solution has potential to reduce germination, perhaps pushing a few vulnerable individual seeds over the edge.
Given all the potential problems in producing and maintaining high germination percentages, it is amazing that our seed industry provides high quality seed to their customers.
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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.