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Seed Dormancy

In some cases, viable seeds will not germinate when exposed to ideal growing conditions. This is due to dormancy. Dormant seeds are healthy and well developed, but for a variety of reasons they are not ready to germinate.  Although this is a common trait for seeds of many species, it does present some problems for the commercial seed trade.  Most growers desire rapid, uniform growth from seeds planted in a field or greenhouse. A seed lot that shows slow, uneven growth can be of limited value.

At AMM we are always watching so see if dormancy is a factor.  If we suspect dormancy in a germination test, we will run a retest using one or more of the prescribed methods for breaking dormancy.  We compare this test to the original test to calculate the amount. Germination of the standard test plus dormant seeds equals total viable seed.  When dormancy is observed in a crop kind with no effective method for breaking dormancy, or if the seeds do not respond to the extra procedures, we report dormancy ‘not determined’ on the seed analysis report.

In commercially produced vegetable and agricultural crops, dormancy is usually associated with seed freshness, and will often dissipate after a short period of time.  Some native and re-vegetation species show persistent dormancy that may last for  years, and can be very difficult if not impossible to beak in the laboratory.

The viability of un-germinated seeds can also be determined with the use of TZ (Tetrazolium). This is a very accurate assessment of overall viability, but it may not reflect what can be expected to germinate within a reasonable period of time.

In the seed testing protocols, there are several prescribed methods for breaking dormancy, and getting stubborn seeds to germinate. The most common methods include:

  • The addition of chemicals to the testing substrate, such as Potassium nitrate (KNO3) or Giberrellic acid. These substances enable some of the bio-chemical processes that occur within seeds to induce the germination process.
  • Pre-chilling, in which the germination tests are prepared as usual but placed into a cold chamber (usually 5° or 10°C) for a prescribed interval before being placed in the growth chamber. This simulates the cold season the seeds would endure before favorable growing conditions occur.
  • Scarification, in which the seed coat is physically or chemically etched to allow moisture and gases to penetrate more readily.