In Vitro Germination of Ostrya virginiana (Mill.) K. Koch using Gibberellic Acid As a Substitute for Overcoming Seed Dormancy

Ostrya virginiana (Mill.) K. Koch (American Hophornbeam) is a member of Betulaceae and is primarily found in the eastern United States, usually as an understory tree. It grows in USDA hardiness zones 3–9. American Hophornbeam is commercially propagated only through seed, with no clonal propagation methods reported within the species. Currently, American Hophornbeam seed requires 60 days of warm stratification followed by 120–140 days of cold stratification. The purpose of this study was to determine if seed dormancy could be overcome in vitro using gibberellic acid (GA₃). Seed was collected from the accession lines located at the North Dakota State University Horticulture Research Farm during late fall. A 6 x 2 factorial experiment was used with GA₃ concentrations at 0, 0.5, 1.0, 2.0, 2.5, or 5 μM. The second factor was light versus dark. MS basal medium was used supplemented with 3.0% sucrose and 0.8% agar. Seed grown in light was incubated approximately 30 cm beneath cool white fluorescent lamps that provide a photon flux of approximately 40 μmol·m^-2·s^-1 for a 16-h photoperiod at 25±3 °C. Seed grown in the dark was incubated at 25±3°C. Seed was left in the treatment medium for 7 weeks, at which time they were evaluated for germination. Seed was considered germinated if the radicle or hypocotyl emerging from the seed coat was ≥ 5mm. Initial results indicate the presences of GA₃ under no light conditions is needed for germination of American Hophornbeam seed. As the concentration of GA₃ increases, so do germination rates. Further research needs to be conducted ex vitro on non-stratified seed of Ostrya virginiana to determine if gibberellic acid could be utilized by commercial seed propagators to significantly reduce the long stratification period.