Novel Approaches for Improving Root Development in Bougainvillea Spectabilis Alexandra Stem Cuttings Using Hormonal and Physical Stimuli

This study aimed to enhance the propagation efficiency of Bougainvillea spectabilis Alexandra by evaluating the synergistic effects of auxins (NAA and IBA), bottom heat, and blue light durations on rooting performance of stem cuttings under controlled conditions. A full factorial experiment in a completely randomized design with three replications was conducted. Factors included auxin types (NAA, IBA) at 0, 5, and 10 mg/L, bottom heat (±), and blue light durations (0, 2, 4 h/day). Parameters assessed were callus formation, shoot survival, root fresh/dry weight, rooting percentage, and rooting time. The combination of IBA at 10 mg/L with bottom heat and 2 h/day blue light significantly improved rooting percentage (88.7%), root fresh weight (396 mg/cutting), root dry weight (75.3 mg/cutting), and shoot survival rate (95%), while reducing rooting time to 50 days. Correlation analysis showed strong positive relationships between rooting percentage, root biomass, and shoot survival, and negative correlations with rooting time. The study was limited to one specific cultivar (‘Alexandra’) and controlled greenhouse conditions; further validation under commercial production settings is needed. This research provides a cost-effective and sustainable protocol for improving the propagation of woody ornamentals by integrating low-dose IBA with environmentally friendly physical stimuli (bottom heat and blue light), enhancing commercial production efficiency.