Influence of biostimulants and indole-3-butyric acid on seasonal rooting performance, growth, quality and biochemical dynamics of difficult-to-root Bougainvillea ‘Thimma’

Achieving higher percentage and uniform rooting in difficult-to-root variegated Bougainvillea cultivars remain a challenge for nurserymen. In this study, 20 cm hardwood cuttings of Bougainvillea peruviana ‘Thimma’ were treated with different biostimulants including seaweed extract, coconut water, willow bark extract, Saridex powder and indole-3-butyric acid (IBA) at concentrations ranging from 500 to 6000 mg L-1 during rainy and spring seasons. The cuttings were placed into sand beds under partial shade in completely randomized design in three replications. Results indicated that cuttings treated with IBA at 4000 mg L-1 during the rainy season yielded promising outcomes, with earliest root initiation (33.8 days), highest survival rate (80.7%), and maximum rooting (70.0%). Coconut water-treated cuttings also showed comparable results, with a survival rate of 60.0% and a rooting percentage of 53.3% compared to control. Biochemical analysis further revealed seasonal variation across treatments, with total soluble sugars ranging from 60 to 220 mg g-1, proteins from 20 to 45 mg g-1, and polyphenol oxidase activity from 25 to 130 µ ml-1. The findings indicate that treating Bougainvillea ‘Thimma’ cuttings with IBA at 4000 mg L-1 during the rainy season enhances rooting and survival percentage, improves plant quality, and increases propagation efficiency.