Tetrazolium
The Tetrazolium test measures potential germination. This is most commonly used on small-seeded crop species, but we demonstrate it on large seeded crops to facilitate viewing the test. The chemical compound 2,3,5 tetrazolium chloride is a white powder, mixed with water to a range of 0.1 to 1% solution and stored in a dark bottle (to avoid light) in a refrigerator.
Seed are pre-conditioned to take up (imbibe) water slowly by placing in wetted blotter paper overnight. Seed that takes up water too rapidly can rupture cells, giving a false reading.
After pre-conditioning, the seed often has to be cut to allow the tetrazolium solution to rapidly move into the seed. Corn is split in half longitudinally.
Soybean and bean cotyledons are split apart.
And wheat germ is split longitudinally.
Then placed into the tetrazolium solution to soak for several hours.
The living tissue in the seed (the germ or embryo) turns red within a few hours. The reaction that causes the change in color is related to the respiration rate. Red or pink tissue means that the tissue is healthy and is respiring normally, black that the tissue is respiring rapidly due to either injury or being a meristematic area, and white is dead tissue with no respiration.
This is a corn kernel changing color.
This is a wheat seed changing color.
Based upon the color and location of dead or injured tissue, a potential germination percentage can be determined.
In this case, all eight wheat seeds are healthy and would be expected to germinate.
In this case, all five corn kernels are healthy and would be expected to germinate.
This soybean sample has some dead tissue in the cotyledon, thus its potential germination is lower than 100%. The biggest advantage of this test is that it is rapid, and can be used on plant species for which standard warm germination guidelines have not been established. The largest disadvantage is that this test requires the use of a highly trained seed technologist.