tetrazolium chloride - TZ test (developed by Germans around 1943) :
Hydrated seeds are perforated and placed overnight into a solution of tetrazolium chloride. This compound is colourless until in the presence of living tissue when it is converted to a red dye. This causes living tissue to stain red. Seed staining patterns are examined the following day to determine percentage seed viability. Only uniformly stained red / dark pink embryos are considered 'viable'. However, the TZ test can be highly subjective.
The white compound is enzymatically reduced to red TPF (1,3,5-triphenylformazan) in living tissues due to the activity of various dehydrogenases (enzymes important in oxidation of organic compounds and thus cellular metabolism), while it remains as white TTC in areas of necrosis since these enzymes have been either denatured or degraded.
Ref: International Seed Testing Association (ISTA). 2003. ISTA Working Sheets on Tetrazolium Testing. Vols. I and II. ISTA, Bassersdorf, Switzerland.
Other ways: dead seeds of brassicas and some other plants have leakage of secondary metabolites (sinapine), aminoacids and soluble sugars (see US 4975364 A A method of determining the viability of crucifer seed, for example cabbage seed by detecting leakage of sinapine from non-viable seeds).
Please, consider also this reference:
Simić A., S. Sredojević, M. Todorović, L. Đukanović and Č. Radenović (2004). Studies on the relationship between content of total phenolics in exudates and germination ability of maize seed during accelerated aging. Seed Sci. Technol., 32, pp. 213-218.
This method could be good not just for maize, but also for the other crops. The best results were obtained on soybean seeds.
I know the bio chemical method tetrazolium too, but the method must be ajusted for different species and corelated with seed size for time in overnight.
Hi Dr. Alex,
Standard Tetrazolium test is not sufficient to test the viability fo your seeds? I will send you the protocol to your email. find the attached file,
Tetrazolium (TTC), 2,3,5-tri-phenyltetrazolium chloride, stains living tissues
red. This chemical can differentiate between viable and non-viable seeds, and an
experienced technician can tell exactly how fresh and vigorous a seed is and whether or not vigor is decreasing. Highly viable seeds are uniformly red, whereas seeds of reduced vigor are white and/or speckled white. Deeper red spots, especially on low viability seeds, may represent microbial respiration
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