Evaluation of different hormonal and temperature treatments on dormancy breaking of Lavender (Lavandula angustifolia) seed

Extended Abstract Introduction: Lavandula angustifolia L. is one of the most important plants belonging to Lamiaceae which has abundant use in traditional and pharmacological medicine. Lavender seed dormancy is one of the problems in producing seedlings which increases seed consumption. In this regard, an experiment was carried out to investigate different treatments for seed dormancy elimination of Lavender and measuring germination and growth indices. Materials and Methods: An experiment was conducted in a completely randomized design with three replications at the Ecophysiology Laboratory of Karaj Institute of Medicinal Plants in 2018. The experiment consisted of 14 treatments on seed dormancy elimination. The treatments included the control, hormonal treatments (Gibberellic acid with 250, 500, 750 and 1000 mg/l concentrations) and Prechilling treatments (7, 14 and 21 days of refrigeration). The integrated treatments were 7 days refrigeration + 500 mg/l gibberellic acid, 14 days refrigeration + 500 mg/l gibberellic acid, 7 days refrigeration + 1000 mg/l gibberellic acid, 14 days refrigeration + 1000 mg/l gibberellic acid, 30 minutes at 40 ° C water + 14 days refrigeration, and 30 minutes at water 40 degrees +14 days refrigeration + 500 mg/l gibberellic acid. Results: The results showed that the highest germination percentage (70.67%), germination rate (24.26%) and germination index (246) were achieved in 750 mg/l Gibberellic acid, and the highest epicotyl length (5.09 cm), seedling length (6.23 cm) and seedling fresh weight (0.57 gr) were produced with 500 mg/l Gibberellic acid. Also, the lowest mean germination time (MGT) (4.12s day) was obtained in 1000 mg/l Gibberellic acid treatment. Also, 7 days of refrigeration + gibberellic acid at 500 mg/l treatment had no significant difference with the other concentrations of gibberellin treatments. Therefore, low gibberellin concentration with 7 days of prechilling had the same effect as higher gibberellic acid concentrations. In addition, 14 days of refrigeration + 1000 mg/l gibberellic acid treatment and treatment of 30 min in water at 40 ° C +14 days prechilling + 500 mg/l gibberellic acid produced the lowest shoot (0.78, 0.82 cm), seedling height (0.99, 1.04 cm) and fresh weight (0.013, 0.01 gr) that showed the negative effects of increased prechilling time and water at 40 ° C, Conclusion: It was finally found that the lavender seed dormancy type is physiologically non-deep and moderate and Gibberellic acid is a suitable substitute for prechilling. The best treatment was gibberellic acid with a concentration of 750 mg/l to break the dormancy of lavender seeds. Highlights: Gibberellic acid is a good substitute for prechilling in seed dormancy elimination of lavender. Breaking the dormancy of the lavender seeds is necessary for producing seedlings from the seeds of this plant.