Agriculture Reference
In-Depth Information
5
Germination
and Viability
Testing
Seeds are tested for germination to determine how they will perform when planted in the ield, the garden,
or in a seedling nursery. This information is also needed for labeling and marketing purposes or to deter-
mine if a seed lot has been properly labeled when sold or offered for sale.
Although seeds have been tested for germination for hundreds of years by critical gardeners and farm-
ers, it has only been in the past 150 years that laboratory germination has been developed to provide farmers
and other seed users assurance of the quality of seed produced on their own farms as well as that purchased
from others.
Conducting a Standard Germination Test
Reproducible germination results require test conditions that are uniformly applied. Thus, both the AOSA
and ISTA rules prescribe standardization conditions of optimum substrata, temperature, light, time of evalu-
ation, methods of overcoming dormancy, and speciic criteria for determining normal and abnormal seed-
lings. Development of these uniform rules and procedures represents the single most important contribu-
tion to the standardization of seed testing. Thus, the rules are an invaluable asset to the seed analyst in the
performance and interpretation of germination tests.
The AOSA and ISTA rules deine procedures for germinating seeds of different species, including
substrata, temperature, timing of evaluation, duration of test, and additional directions such as the use of
light and other means of breaking dormancy. Since both AOSA and ISTA rules have similar germination
requirements for most species, examples cited in this chapter are mostly from the AOSA rules.
SEEd SELECTIon, PrEPArATIon, And PLAnTInG
Seeds for the germination test are taken from the pure seed portion of a seed lot. The counting and selection
of the seeds must be made randomly without regard to size or appearance. Selection may be made by hand,
a counting board, or with a vacuum seed counter. When only germination results are needed, the pure seed
portion must be at least 98% pure; otherwise, pure seed must be separated by standard purity test procedures
to provide seeds for germination (see Chapter 4). At least 400 seeds must be tested except that 200 seeds
may be used for kinds comprising 15% or less in seed mixtures. Germination tests are conducted in repli-
cates of 100 seeds or less to avoid crowding on the substratum. Grass spikelets or multiple units regarded
as “seed units” or deined as pure seed are considered and germinated as a single seed. Only one sprout or
seedling that emerges from a spikelet (e.g., Poa ) or multiple unit is counted. This also applies to complex
fruiting structures such as those found in garden beets or New Zealand spinach.
59
Search WWH ::




Custom Search