Comparing procedures for performing tetrazolium test on carrot seeds

Abstract

The tetrazolium (TZ) test is one of the main methods to estimate vitality or viability and seed vigor. The aim of this study was to improve the methodology and reduce the execution time of tetrazolium test on carrot seeds, considering two existing references on this subject. Eight lots of ‘Brasilia’ carrot seeds were used. The hydration, during the pre-conditioning of the seeds, was done in two ways: directly in water during 18 hours and in rolls of filter paper during 2 hours. Seed color was analyzed through combinations between cutting types, concentration, period and temperature used during contact with the TZ solution. Three types of longitudinal cutting were used, before immersion in the tetrazolium solution: a) lateral and as distant as possible from the embryo distal to the embryo; b) partial, in the distal region opposite to the embryo, on about 1/3 of seed length; c) lateral and near the embryo, without reaching it. The used TZ concentrations were 0.1; 0.5 and 1.0%; periods of contact of the seeds with TZ solution were 1, 2, 6 and 24 h and temperatures were 30 and 35°C. The experimental design was completely randomized, with 5 replicates of 20 seeds per lot, per procedure. The results obtained through TZ test were compared with the results obtained in germination and seedling emergence tests. We could make hydration period shorter, from 18 to 2 hours, and staining from 24 to 2 hours. The lateral cutting as close as possible to the embryo, without reaching it, used in preparing the staining, should be emphasized for making execution and interpretation easy. The combination of higher efficiency used for hydration rolls of filter paper during 2 hours and, for staining lateral cutting as close as possible to the embryo, without reaching it, with the development of staining during 2 hours in 0.1% TZ solution at 35ºC. Thus, the reduction of the maximum tetrazolium test time, considering hydration (18 hours) and staining (24 hours), was from 42 to 4 hours and showed to be a feasible and reliable alternative.