Weather conditions are an issue
The adverse weather conditions that played havoc on seeding and harvesting for the 2010 and 2011 crop season left a lot of seed users very uncertain about seed quality.
And it seems that the most frequently asked question for us has been about the overall effect of dormancy on seeding potential and also what causes it. Dormancy in cereals last year was widespread and became very troublesome as we got closer to seeding in 2011, because in some cases it could not be broken in laboratory conditions. This year seed users are wary about testing early and are putting their seed into the freezer before sending it in for testing. It is true that cold temperatures will break dormancy eventually. In fact as seed is exposed to the cold conditions in the bin over the winter the dormancy will disappear. However, a laboratory is equipped with the knowledge to overcome dormancy issues early on in the season and its better to know sooner than later. Other issues may be overlooked if seed is not tested early. My thoughts on the subject are that a seed user should test once after harvest, again after processing and again after treatment. This is backed up in the Canadian Seed Institute manual and the Canada Seeds Act.
Dormancy is complicated because there are several types, and it is often confused with dead seed.
A seed analyst has to know how to identify dormancy and how to overcome it. You will note that we refer to dormancy as fresh ungerminated seed. These are seeds that remain firm at the end of the prescribed test period. The seed will have imbibed water and will appear very plump and healthy. The ungerminated seed when cut in half will have a clean appearance unlike a decayed seed which is dead. The tissue of the seed has to be perfectly white or yellow depending upon the crop to be called dormant, any necrotic spots will lead to decay and these will eventually die. Dormancy can mask other quality issues such as chemical damage and frost, both of which can be detrimental to the germination. Also, having an accurate germination value is imperative for the field planting potential.
Endogenous dormancy is the most common form of dormancy. This is when a seed has an excess of a germination inhibitor such as abscisic acid (ABA). This happens when the seed is not physiologically mature and has high moisture content. Subjecting the seed to very cold conditions will relieve this type of dormancy naturally. The seed laboratory of course can also manipulate the seeds ability to germinate, by using growth regulators such as Gibberellic acid or Potassium nitrate. Also changing temperatures, exposing the seed to more light or drying the seed will almost break the dormancy. The most popular method for breaking dormancy in any laboratory is by Prechilling the seed at 7ºC for a number of days, usually 3 days, before moving the seed to the germination chamber which is operating at 20ºC.
We are very aware of dormancy every year, and you can be confident that if it is present we will do everything we can to alleviate the concern, because we must achieve the highest germination result we possibly can.