The effect of gibberellic acid and potassium nitrate on seed dormancy of fourteen medicinal plant species ( Lamiaceae)

To study the effect of gibberellic acid and potassium nitrate treatments on germination and seed dormancy of 14 medicinal plant species from the Lamiaceae, that were collected in the spring and summer of 1392 from their natural habitates in Kerman province, two separate laboratory experiments were conducted at 20-24 centigrade degree, based on completely randomized design with 4 replications of 25 seeds. In the first experiment, seed germination was considered in H2O. The results indicated that the highest germination percentages were observed in Ocimum basilicum (%96) and Salvia macrosiphon (%95) while the lowest germination were obtained in Marrubium crassidens (%5) and Nepeta bracteata (%0). In the second experiment, the effect of seed dormancy breaking treatments such as gibberellic acid (GA3) with 3 concentrations (250, 500 and 1000 ppm) and potassium nitrate with 2 concentrations (500 and 1000 ppm) were practiced on the germination of 10 plant species with low germination (below %80) in H2O. Dormancy breaking treatments were effective on 9 species (i.e. Marrubium crassidens and Ocimum santum) out of 10 species. In most studied species, dormancy breaking treatments increased germination percentage and Mean Germination Time were reduced. Therefore, based on their reactions to the treatments, it was found that these 9 species have physiological dormancy.