CASPIAN HONEY LOCUST (Gleditsia caspica) is one of the valuable species that ecologically and socially plays a significant role in northern forests of Iran. This investigation is aimed to study of somatic embryogenesis process using different plant growth regulators (PGRs). The leaves of in vitro seedlings used as explant for callus induction on half-strength Murashige and Skoog (MS) medium containing different PGRs. The results showed that the used plant growth regulators in different concentrations had significant effects on callus induction from leaf explants, somatic embryogenesis, the somatic embryos development and maturity, and also shoot regeneration. Half-strength MS medium containing 4.5 μM 2,4-dichlorophenoxyacetc acid (2,4-D) and 2.2 μM benzyl adenine (BA) was the most effective PGR treatment for callus induction. The morphologically embryogenic calli and formation of globular embryos were achieved on medium containing 0.54 μM naphthalene acetic acid (NAA) along with 2.3 μM Kinetin (KIN), and the medium containing 2.7 μM NAA in combination with 2.3 μM KIN. The results showed that half-strength MS medium containing 60 mg l-1 sorbitol, 2.3 μM 2,4-D and 1.3 μM BA was the best medium for development and maturation of somatic embryos. The highest shoot regeneration of somatic embryos was obtained on half-strength MS medium supplemented with 9.2 μM KIN.
