Effects of Different Concentrations of Plant Growth Regulators on Callus Induction and Shoot Regeneration in St. John’s Wort (Hypericum perforatum)

St. John’s wort belongs to Hypericaceae family and has been used since ancient Greeks as a herb for the treatment of anxiety, depression, wounds and burns. In present study, the effects of different concentrations of CPPU and BA (each in three concentrations) in combination with two concentrations of IAA on callus production and shoot regeneration of Hypericum perforatum from leaf and stem explants were evaluated to identify the best growth regulator combination for obtaining the highest yield of in vitro regenerated shoots. This was implemented in a CRD-based factorial experiment with three replicates and five samples in each replicate and the traits including callus fresh weight, number of shoots, shoot length, length of the tallest shoots, and the number of nodes of the tallest shoots were measured and examined. Results showed that the most effective combination for regeneration was 1.5 mg/l CPPU and 1 mg/l IAA, which may be a proof for more effectiveness of CPPU in comparison with BA as cytokinin source on shoot regeneration in Hypericum perforatum. The use of 1 mg/l IAA in combination with 1.5 mg/l CPPU or BA resulted in a significant increase in shoot regeneration. It was also showed that 1 mg/l IAA in combination with 0.5 mg/l BA could cause a significant increase in callus fresh weight.