Auxins and Cytokinins Regulate Abscission and Physiological Changes of Flowers in Cut Dendrobium cv. Eiskul Inflorescences

The effects of auxins and cytokinins on quality and physiological changes in cut Dendrobium cv. Eiskul inflorescences were studied at Ubon Ratchathani University, Thailand. The auxins tested were indoleacetic acid (IAA), indolebutylic acid (IBA), and naphthaleneacetic acid (NAA). The cytokinins tested were 6-benzylaminopurine (BAP; also called benzyladenine) and 6-furfurylaminopurine (kinetin). The hormones were supplemented in a vase solution, at 5, 25 and 50 mg L-1. All auxins tested extended the vase life of Dendrobium inflorescences by delaying senescence and inhibiting abscission of open flowers. The high concentrations of auxins were effective and increased ovary size. NAA, applied at 50 mg L-1 completely prevented abscission. This treatment could induce greening of the normally whitish pedicel, indicating that it reverses a number of developmental processes. Cytokinins had no effect on vase life and ovary size but BAP at 50 mg L-1 inhibited abscission of open flowers. The application of hormone treatments, IBA or BAP at 50 mg L-1 or a combination of 50 mg L-1 IBA and 50 mg L-1 BAP, prior to ethylene fumigation, prevented open flower abscission and decreased ACS activity in flowers. These results suggest that adding auxin hormones in the vase solution has the potential to improve cut flower quality and could be used as a commercial vase solution.