Determination of optimum concentration and time of Stevia (Stevia rebuadiana Bertoni) seed priming by Selenium

Selenium is an essential nutrient, but its role in the plants need more research. For this purpose a factorial experiment in a completely randomized design with three replications was carried in the Shahed University of Tehran in 2015. The first factor was different concentrations of Selenium (0, 0.5, 1, 1.5 and 2 percent) and the second factor of priming time (0, 8, 16, 24 and 32 hours). The results indicate that the effect of the concentration and priming time was significant on germination percentage, germination rate, mean daily germination, germination uniformity, germination value, seedling length and vigor index. The interaction of concentration in priming time had a significant effect on the level of one percent on traits of germination rate, mean time germination, daily germination rate, germination uniformity and seedling length. With increasing concentrations of selenium from 0 to 2%, were observed significant increases in germination percentage, germination rate, mean daily germination, germination value, and seed vigor index. So that the highest average traits observed in concentrations of 2% and lowest in 0%. The highest germination rate in priming for 8 and 24 hours in concentration of 2% with an average of 4.50 and 4.33 seeds per day, respectively. With increase of priming time increased germination uniformity and seed vigor and highest average of two traits was 24 and 32 hours priming. Generally, priming with 2% concentration for 24 hours had significantly increased germination index and seed vigor of Stevia.