Effect of hormone priming and hydro priming on Stevia (Stevia rebaudiana Bertoni) seed germination under salt stress

In order to evaluate effect of time period of hormone and hydro priming on Stevia seed germination indices under salt stress a factorial experiment based on completely randomized design (CRD) with three replications was conducted in Seed Science and Technology Laboratory of Shahed University of Tehran in 2015. The studied factors consisted of seed pre-treating by gibberellic acid and distilled water for 0, 16, 24 and 48 hours and salt stress (2.5, 5, 7.5 and 10 dS.m-1). Germination percentage and speed, mean time of germination, mean of daily germination, daily germination speed and germination value was measured. Results showed that salinity× hormone priming interaction significantly influenced germination percentage and germination speed, mean daily germination and germination value. The highest germination percentage and germination speed was seen in 5 dS.m-1 and 48 hours hormone priming interaction and 2.5 dS.m-1 and 48 hours hormone priming interaction respectively. The highest daily germination speeds was seen in 0 dS.m-1 and 16 hours hydro priming interaction and 0 dS.m-1 and 16 and 24 hours hormone priming interaction respectively. Hormone priming of stevia seed by gibberellic acid for 24 and 48 hours could improve stevia seed germination parameters. Some of germination parameters (rate and percentage of germination) were reduced by salinity stress.