Metodologia do teste de tetrazólio em sementes de Albizia polycephala (Benth.) Killip

Abstract

The use of the tetrazolium test in seed quality control is widespread, as it speeds up the handling of batches for the market, obtaining entirely reliable information in advance and quickly. However, to ensure its speed and effectiveness, it is necessary to define specific conditions for preparing and coloring the seeds. Albizia polycephala (Benth.) Killip, belonging to the Fabaceae family, and popularly known as angico-branco, is a species endemic to Brazil, occurring in the Caatinga. The white angico is a rare tree species, technically very little known. In this context, the objectives of this work were to establish the most appropriate procedure for conducting the tetrazolium test to evaluate the viability and vigor of A. polycephala seeds, concomitantly with its optimization. To standardize the tetrazolium test, a completely randomized experimental design was used, in a 2x3+1 factorial scheme (two concentrations of tetrazolium solution x three periods of coloring + control = germination test), with four replications of 25 seeds. Only the cotyledons containing the embryo were placed in 50 mL plastic cups, and immersed in a solution of 2,3,5-triphenyl tetrazolium chloride salt, at concentrations of 0.05 and 0.075%, for staining periods of 1. 2 and 3 hours, in a Biochemical Oxygen Demand type chamber at 30 oC in the dark. The evaluation of the physiological potential of the five lots of A. polycephala seeds was carried out using a completely randomized experimental design, with four replications of 50 seeds. The best condition of the tetrazolium test was applied to seeds harvested in 2022, and recently harvested seeds (2023). Based on the coloring and health standards of the tissues, seeds whose embryonic axis showed a pink color were classified as viable, and seeds with a discolored embryonic axis or a very intense yellow or red color as non-viable. Classes 1 and 2 identified viable and vigorous seeds. A. polycephala seeds classified in Classes 1 and 2 showed greater physiological potential, with germination of 99% and germination uniformity of 0.5439 bits. Class 3 identified viable and non-vigorous seeds. Seeds of A. polycephala classified in this class germinated and produced normal seedlings only under ideal conditions. Class 4 identified non-viable seeds. Damage shown in this class compromised the normal development of A. polycephala seedlings. The most appropriate procedure for conducting the tetrazolium test to evaluate the viability and vigor of A. polycephala seeds is the use of a concentration of 0.05%, for a concentration period of 3 hours.