Dendrobium Hybrid Flower Number and Pedicel Curvature is Influenced by the Application of Gibberellic Acid and Indole-3-acetic Acid

Mostly, orchid flowers undergo a process of resupination before blooming because of twisting or rotation of the pedicel at the bud stage, positioning the lip below all other floral segments. Indole-3-acetic acid (IAA) and Gibberellic acid (GA3) are key plant hormones associated with growth and flowering. However, the effects of their exogenous addition on the flower number, pedicel length, and pedicel curvature in the popular orchid Dendrobium Burmese Ruby, Bee Lian 1989 × Dendrobium Mae-klong, S.Semachai 1975 are largely unknown. This study tested plant responses to exogenous GA3 and IAA in terms of flowering pattern and pedicel curvature of a Dendrobium hybrid (Dendrobium Burmese Ruby × Dendrobium Mae-klong). Exogenous application of GA3 significantly increased flower number and pedicel length, and decreased flower size, while flowers were resupine with a similar pedicle curvature to the non-treated (control) flowers. On the other hand, exogenous application of IAA significantly reduced flower number and inhibited the resupination process with no significant changes in pedicel length or flower size. These results indicate that IAA and GA3 play important roles in determining flower number and resupination in Dendrobium hybrid (Dendrobium Burmese Ruby, Bee Lian 1989 × Dendrobium Mae-klong, S.Semachai 1975).