The objective of this research was to determine the conditions to evaluate the viability of Brachiaria brizantha seeds by the tetrazolium test. Using eight seed lots, preconditioning periods and temperatures (2, 4 and 6 hours at 35ºC and 40ºC; 6 and 16 hours at 30ºC, between paper) and staining periods and temperatures (1, 2 and 4 hours at 35ºC, 40ºC and 45ºC; 6 hours at 30ºC, bisected seed through the embryo, immersed in an aqueous solution of 0.075% tetrazolium chloride) were tested. The tetrazolium test was performed classifying the seeds in two categories: viable and non- viable. Seed water content (oven method, 105±3ºC/24h) and germination (TP, 20-35ºC, count at 7, 14 and 21 days) were determined. The experimental design was a randomized block with four replications for each seed lot. The multiple mean comparison within treatments was performed using Tukey's test at a 0.05 error level. It was concluded that the tetrazolium test constitutes an efficient option for estimating the viability of Brachiaria brizantha seeds. The most adequate condition would be that resulting from a combination of six hours of preconditioning at 30ºC (seed water content was 25%) followed by a two hours of staining at 40ºC.
Brachiaria brizantha; seed analysis; germination
