CORRELAÇÃO ENTRE OS TESTES DE PH DO EXSUDATO E TETRAZÓLIO EM SEMENTES DE SOJA

Abstract

The tetrazolium test allows the evaluation of seed vigor and viability; however, although it is fast, it requires special training on the embryonic structure of seeds and interpretation techniques. The exudate pH test has been used to evaluate the vigor of seed lots visually and instantly. The objective of this study was to study variations and combinations of the parameters involved in the exudate pH test and to correlate them with the vigor and viability of the tetrazolium test, allowing the safe and rapid identification of the vigor levels of soybean seed lots. Initially, germination and vigor tests (first count, electrical conductivity and tetrazolium) were performed on three soybean seed lots. Afterwards, four replicates of 25 seeds were distributed in plastic trays divided into unit cells. Three amounts of water inside the cell (2, 3 and 4 mL) and three amounts of drops of phenolphthalein and 0.8% sodium carbonate were tested, being 1+1; 2+2 and 3+3, respectively. The drops of the solutions were added after 30 minutes of imbibition at 25 °C. The reading was performed immediately afterwards, being interpreted based on the color of the solution, being strong pink for viable seeds and colorless or weak pink solution for non-viable seeds. The experiment was carried out in a completely randomized design with four replicates, and the means were compared by the Scott-Knott test at 5% probability. Principal Component Analysis and Pearson's correlation network were also performed between the exudate pH test and the vigor and viability of the tetrazolium test. There was a high correlation (>0.9) of vigor and viability (tetrazolium) with the combinations 1 drop and 2 mL, 1 drop and 4 mL and 2 drops and 4 mL. Furthermore, there was a negative correlation between the combination of 3 drops and 3 mL with vigor and viability, indicating that this is not an option for testing the pH of the exudate in soybean seeds. The pH test of the exudate was strongly correlated with the tetrazolium test in soybean seeds, in the combinations of one drop of each solution (phenolphthalein + sodium carbonate) in 2 or 4 mL of distilled water, or two drops of each solution in 4 mL. This methodology for testing the pH of the exudate is efficient for ranking the vigor of soybean seed lots.