Agriculture Reference
In-Depth Information
Although it is not usually possible to accurately determine variety on the basis of visual examination
of seeds, it should be done whenever possible or required. A comprehensive discussion of varietal testing
appears in Chapter 9.
Pelleted, Coated or Encrusted Seed
Seeds which are enclosed in nonseed inert matter associated with pelleting, coating or various incrustations
must be physically separated from the nonseed inert matter for determining the percent pure seed. This may
be accomplished by various procedures, but is usually done by soaking in water or diluted sodium hydrox-
ide solution. The seed sample is irst weighed, then the inert material dissolved by soaking in water, then
allowed to dry overnight at room temperature before reweighing and calculating the percent inert matter.
Detailed procedures are described in the AOSA and ISTA rules.
Fig. 4.10. Examples of (left) single-seed units, and (right) multiple lorets in chewings fescue (courtesy of
Oregon State University Seed Laboratory).
Testing Grass Seeds Containing Multiple florets
Several grass seed crops contain seed units in which an immature, sterile loret is attached by a rachilla to
a well-developed loret from the same spikelet (Figure 4.10). Individual separation of each multiple loret
into pure seed and inert components may require too much time to be practical; however, it can be done.
An alternative method of determining the purity of such samples consists of estimating the amount of pure
seed represented in the fertile lorets by applying a correction factor to the weight of the multiple lorets.
Factors to apply for multiple unit determinations are given in the AOSA rules. These factors represent
the percentages of the multiple seed unit weights that are considered pure seed. The remaining percentage
is regarded as inert matter.
