Tetrazolium test in wild-mangaba seeds (Lafoensia pacari St. Hil. - Lythraceae)

Abstract

Lafoensia pacari seeds have longevity of over four months; however, when they are exposed to adverse weather conditions their viability is dramatically reduced. The development of quick evaluation methods for the physiological quality of seeds can help in the decision-making process of whether to use or not seeds intended for the production of seedlings. This work had the objective of studying the tetrazolium test methodology in wild-mangaba seeds in order to determine the best temperature conditions, staining period, and tetrazolium solution concentration. Pre-conditioning consisted of imbibition of the seeds in distilled water, at 25ºC, for 48 hours; in the first hour, each sample was submitted to agitation (magnetic stirrer); immediately afterward the samples remained immersed in water for another 47 hours, under the same temperature. Next, the integuments of two sub-samples of 20 seeds were removed, exposing the embryo and avoiding separation of the cotyledons. Treatments consisted of four tetrazolium concentrations (0.075; 0.1; 0.5; 1%), three incubation temperatures (30, 35, and 40ºC), and 8 evaluation periods. Staining development was evaluated at every 30 minutes, and the most suitable period for viability evaluation was determined. The results obtained demonstrated that, regardless of incubation temperature, when in a 0.075% solution, the seeds were adequately stained between one and four hours; when in the 0.1% concentration solution, they were adequately stained between one and three and a half hours; in the 0.5% solution, a satisfactory result was obtained between one and two hours; when the solution was at the concentration of 1%, 30 minutes were sufficient to develop staining. It is concluded that the pre-conditioning by immersion in water for 48 hours, with integument removal and immersion in a 0.075% tetrazolium solution, at the combination of 40ºC/60 minutes, were effective to determine the viability of L. pacari seeds.