2017 ASHS Annual Conference

Bougainvillea cultivars are widely used ornamentals valued for their ability to bloom profusely while tolerating poor growing conditions such as pollution, compaction, and drought stress. Bougainvillea x buttiana cultivars are mostly considered qualitative short-day plants that flower more readily and profusely under short day lengths. Water stress has been shown to partially substitute for short-day induction. Ethylene and abscisic acid (ABA) are two drought-stress-related plant hormones that may have an important role to plant in drought-stress-induced flowering in bougainvillea. Ethephon (2-chloroethylphosphonic acid) and ABA were applied to B. x buttiana ‘Afterglow’ to investigate the effects of exogenous applications of ethylene and ABA on the flowering response of this cultivar under non-inductive 14-hour photoperiod. Ethephon applied as a foliar spray at 75ppm concentration and ABA applied as a drench at 150ppm concentration both caused an immediate reduction of endogenous gibberellins in the youngest fully expanded leaves within the first 24 hours of treatment. The treatments also correlated with increased flowering even under the non-inductive photoperiod. The results suggest that ethylene and abscisic acid interfere with gibberellin-dependent photoperiodic signalling in bougainvillea, thus promoting flowering when the plants are under abiotic stress conditions.