Gibberellic acid and benzyladenine promote early flowering and vegetative growth of Miltoniopsis orchid hybrids

Abstract

Flowering of Miltoniopsis orchids is influenced by a combination of cool temperatures and short photoperiod. To determine if application of plant growth regulators could promote flowering without the need for costly structural modification to control photoperiod or temperature, we used drenches of gibberellic acid (GA3) (2.5 or 5 mM), N6-benzyladenine (BA) (25 or 50 mM) alone or in combination. BA (25 or 50 mM) treatments promoted new vegetative shoots and decreased the number of plants with inflorescences compared to the untreated control plants. This reduction of flowering and increased vegetative shoot production was alleviated by the addition of GA 3 in combination with BA. However, the number of plants with inflorescences remained less than the control. GA3 hastened Miltoniopsis inflorescence emergence during the first flowering season by 10.9 to 14.9 days for Bert Field 'Eileen' and by 48.7 days for Rouge 'Akatsuka'. The number of 'Eileen' inflorescences produced per plant increased from 2.2 to 3.0 with 2.5 mM GA3 treatment. Flower deformities were not observed in the GA3 treated plants, and flower size and inflorescence length were unaffected by the GA3 treatment.