Refinement of the Triphenyl Tetrazolium Chloride Method of Determining Cold Injury1

The method of evaluating cold injury in woody plants by the use of triphenyl tetrazolium chloride has been refined to eliminate bias associated with visual differentiation between varying degrees of tetrazolium reduction and to predict tissue survival at a later date. An advantage of the method described here is that a smuall amount of tissue (50-100 mg) is required; this, therefore, allows !for hardiiness determ.nations at precise locations on the plant. The high correlation between cold injury and triphenyl tetrazolium chloride reduction may be due to cofactor and sutbstrate limitations rather than inactivation of dehydrogenases.