By considering these points and planning your seed needs for the
upcoming year as soon as possible, you will help us avoid any delays
that could occur in starting your tests and will enable us to get
the test results to you as quickly as we can.
Seed Test Definitions
Germination of seed in a laboratory test is used
to predict the probability that the seed will produce a normal plant
under favorable conditions. The test measures the percentage of
seeds that germinate and the speed of germination.
Moisture content is the percentage of water held
by the seed. It is calculated by measuring the loss of weight by
the seed when it is dried at a constant temperature for a specific
period of time. Moisture content is a critical factor in storing
seed because seed that is too moist cannot be stored and will deteriorate
Purity distinguishes the amount and type of impurities
in a seed sample. The impurities are physically removed from the
seed sample in the laboratory leaving only the pure seed. A minimum
weight that contains 2500 seeds is needed to conduct the test.
Seeds per pound determines the number of individual
seeds in a pound. This value is used with the germination percentage
and purity percentage to predict the number of seedlings expected
to be produced by a given weight of seeds.
Estimated viability tests are for quickly determining
the number of live seeds in a sample. The tetrazolium, excised embryo,
and x-ray tests are the viability tests used most frequently at
the laboratory. They are the preferred tests for very dormant seeds
(seeds that are difficult to germinate).
In the tetrazolium test, a colorless solution
of tetrazolium chloride is imbibed by the seed. Living tissues then
stain red while dead tissues retain their natural color. Properly
stained seeds are considered viable while improperly stained or
unstained are generally considered non-viable seeds.
In the excised embryo test, the embryos are excised
and incubated under prescribed conditions for 5 to 14 days. Viable
embryos remain firm or exhibit evidence of growth while non-viable
embryos show signs of decay.
X-radiography is used to examine the internal
structures of the seed. It provides a quick, nondestructive method
of differentiating between filled, empty, insect damaged, and physically