The Use of 2,3,5-Triphenyl-Tetrazoliumchloride as a Measure of Seed Germinability

Seed analysts have long been interested in mlletho(ls of mleasturiing the germinability of seeds without the niecessity of a rolutinie germination test, partieuilarly when dealing with dormant seeds or with seeds requiring a Iohig period for the completion of a test. Even with seecds that can be tested in a week or 10 days it is often desirable to klnow within a day the general conidition of a seed lot. This is especially important in the fall season when it is niecetssary to know whether or not an early killing frost has caused damage to the seed crop of corni, sorghum, and soybeans. For dormant seeds, especially the peach, apple, pine, Douglas fir, plumii, hawthorn, European mountain ash, witch hazel, and Rhodotypos kerrioides, normally requiring a long period of after-ripening, it lhas beeni showni byBARTON (1), FLEMION (6, 7, 8, 9) anid others that by excising< the embryos and placing them on moist filter paper in Petri dishes at room temperatuire it is possible to determine their vitality within a period of 5 to 10 days. CROCKER and HARRINGTON (2), DAvIS (3), and LEGGATT (13) have published data indicating that the determination of the catalase ratio of dry and gernniilatiing seeds may serve as a measure of seed viability. MAR (14) has shown that the anmylase activity of soaked oat seed is definitely correlated with geriminability. LAKON (10) aind others (4, 5, 15) have published data on the use of selenium and tellurium salts in solution as a means of determining' the viability of a given seed lot by color reaction of the embryo. LAKON (11, 12) in 1942 comparedIhis results by regular germination test of seeds of oats, barley, wheat, rye, and corn with those obtainied by placinig the cut seeds in a solutiomi of 2,3-diphellyl-5-methyl-tetrazoliumcihloride or 2,3,5-triphleiiyl-tetrazoliumehloride. The resultant staining of the viable embryos correlated well with his germination results. Tetrazoliumlebloride is colorless but forms carmine red formnazans upon reduietion. The salt is thus an oxidation-reduction indicator, and the development of the mion-idiffusible red color in a specific tissue is presumably ail inidication of the presence of active respiratory processes in which hydrogren radicals are tranisferred to the tetrazoliumciehloride. In 1945 a supply of 2,3,5-tripheuyvl-tetrazoliumehloride was obtained by officers of the Chemical Warfare Service in Germany, and Dr. Georg Lakoi prov-ided information about the testing program developed by him in whiel this miiaterial was used. Copies of publications, unobtainable in the past, 1 Journal Paper no. J-1384 of the Iowa Agricultural Experiment Station, Ames, Iowva. Project no. 86.