Determination of Optimum Duration and Concentration of Stevia (Stevia rebaudiana Bert.) Seed Priming with Boric Acid (H3BO3)

Abstract

In order to determine optimal duration and concentration of Stevia seed priming with boric acid for improving germination, an experimental factorial completely randomized design with three replications was conducted in the laboratory of Seed Science and Technology, Shahed University of Tehran in 2015. The first factor was different concentrations of boric acid (0, 0.5, 1.0, 1.5 and 2.0 percent) and the second factor was priming duration (0, 8, 16, 24 and 32 hours). Effects of concentration and priming duration with boric acid were significant on germination percentage, mean germination time, germination rate, germination energy, germination uniformity, mean daily germination, germination daily speed, germination value, seedling length and seed vigor index. The highest values for germination percentage, germination rate, germination energy, means of daily germination, germination value and seedling vigor index were observed after 24 hours of boric acid priming. The highest germination percentage, germination rate, germination potential, germination value and seed vigor index were obtained in 2.0% boric acid priming. 24 hours priming at 1.0% concentration of boric acid had the highest germination uniformity. The seedling length was highest in 24 hours priming at 1.5% concentration of boric acid. In general, Stevia seed priming with 1.5 to 2.0% of boric acid for 24 hours had positive effects on germination indexes and seedling growth.