A Study of the Physical and Physiological Seed Dormancy in Frangula alnus Medicinal Plant

Glossy buckthorn (Frangula alnus), one of endangered medicinal plants, is native to the northern parts of Iran. The present study was carried out in an attempt to investigate and eliminate the physical and physiological dormancy in glossy buckthorn seeds. First, seed viability was analyzed by means of triphenyl tetrazolium chloride test. Then, the permeability and the presence of resistant tissues in the seed crust were analyzed. The mechanical and chemical scarification treatments, respectively with sand paper, knife, and concentrated sulfuric acid (for 2, 4, 8, 20, and 30 minutes), were used to break the physical dormancy of the seeds. For breaking deep physiological dormancy, different concentrations (125, 250, and 500 mg/l) of gibberellic acid and potassium nitrate (100, 200, and 400 mg/l) along with the selected scarification treatments (sharp knife, sand paper, and sulfuric acid) were applied. To determine the chilling requirements, the seeds were treated for 75, 81, 86, 96, and 101 days at 5 ◦C in humid conditions and were then planted. The results of the tetrazolium test confirmed the viability of a high percentage of the seeds. Furthermore, the microscopic analyses illustrated the presence of sclereid layers in the seed crust. The mechanical scarification (with sand paper and knife) and sulfuric acid (30 minutes) treatments significantly increased the permeability of the seed crust. Analyzing the interaction effect of seed crust scarification and chemical treatment for breaking deep physiological dormancy confirmed the significant effect of the scarification treatment with sand paper and knife. Furthermore, the gibberellic acid treatment at 500 mg/l concentration had the greatest impact on breaking the deep physiological dormancy. Analyzing the impact of stratification time on seed germination revealed that the time required for the stratification was more than 100 days.