Tetrazolium (TZ) assay is the fast evaluation for seed viability and alternative quick method for seed’s germinability (Porter et al., 1947; Wharton, 1955). All respiring tissues are capable of converting a colourless compound, TZ (2,3,5 triphenyl tetrazolium chloride) to a carmine red coloured water-insoluble formazan by hydrogen transfer reaction catalysed by the cellular dehydrogenases. TZ enters both living and dead cells but only living cells catalyse the formation of formazan which being non-diffusible stains the viable seeds red whereas the absence of respiration prevents formazan production making the dead seeds (aged tissue) remain unstained.

The brief description of this protocol has been reported in Verma et al., 2013.