The tetrazolium test is a biochemical method in which viability is determined by the red color appearing when cut seeds or isolated embryos are soaked in 2,3,5-triphenyltetrazolium chloride.

Living tissue changes the tetrazolium to an insoluble red compound called formazan. The test is positive for dehydrogenase enzymes in respiration.

Seeds are treated with a 0.1 to 1.0% solution usually for 24 hours.

Photo fo seed partially cut open, showing entire outside of seed dyed red, with white interior.

The seed lot here was treated with tetrazolium. It shows bright red embryos that are viable, pink embryos that are rapidly loosing viability and non-viable embryos that do not stain and are white.

Photo showing the red, pink, and white seeds described by the text.