Effects of plant growth regulators ethephon and s-ABA on flowering of Bougainvillea × buttiana 'Afterglow' under different photoperiods

Bougainvillea cultivars are widely used ornamentals valued for their ability to flower profusely while tolerating poor growing conditions such as pollution, compaction, and drought stress. Bougainvillea × buttiana 'Afterglow' is a qualitative short-day plant that flowers earlier and more profusely under 8-h photoperiod, but water stress has been shown to partially substitute for short-day induction. Abscisic acid and ethylene are two plant hormones related to water stress. The objective of this experiment was to investigate the effects of exogenous applications of s-ABA (ProTone^®) and ethephon (2-chloroethylphosphonic acid) at three concentrations (75, 150 and 300 ppm) on the flowering response of Bougainvillea × buttiana 'Afterglow', under short-day (SD) and long-day (LD). Ethephon applied at 150 ppm and s-ABA applied at 300 ppm induced more profuse flowering than controls under LD. Hormone treatments under SD did not have significant effects on flowering. Further research into the interaction of ABA and ethylene in bougainvillea during and after water stress could yield useful information on how to manage the flowering bougainvillea in container and urban landscapes with limited irrigation.