Which chemical is used to test the viability of seeds?

The chemical that is commonly used to test the viability of seeds is 2,3,5 triphenyl tetrazolium chloride, often referred to as TTC. This compound works by indicating metabolic activity within the seeds. When seeds are viable and capable of respiring, they will convert TTC into a red-colored pigment called formazan. This color change signifies that the seeds have the potential to germinate. The intensity of the color can also provide an estimate of the seed viability, with more intense coloration indicating higher viability.

Other options, although useful in different contexts, do not serve specifically for seed viability testing. Potassium nitrate is often used as a nutrient or in seed treatments to enhance growth but does not directly indicate viability. Calcium chloride has applications in enhancing germination but is not a viability indicator. Silver nitrate is used in various chemical reactions and tests but does not have a role in assessing seed viability. Therefore, 2,3,5 triphenyl tetrazolium chloride is the most appropriate and effective choice for testing seed viability.