Triphenyl Tetrazolium Chloride (TTC) is commonly used as a mitochondrial redox potential indicator for cell death. It is especially useful for seed viability testing and can also detect microbial growth.

TTC is officially recognized by the International Seed Testing Association, and they provide working sheets for testing different seed types for viability. Tetrazolium chloride is a redox indicator that can differentiate between living and dead tissues based on the reduction of TTC to 1,3,5-triphenylformazan, which is red, by dehydrogenases present in the living tissues. This results in living tissues staining a degree of red, while dead tissues remain unstained.

TTC is most commonly used for seed viability testing, but can also be used with algae species, as demonstrated by Zidarova and Pouneva (2006) with Choricystis Minor.