Influence of 6-Benzylaminopurine on Leaf Parameters, Biochemical Characteristics, Essential Oil Yeilds and Composition in Vietnamese Balm - Elsholtzia ciliata (Thunb.) Hyland

Cytokinins promote growth and secondary metabolism in aromatic herbs, but optimal dosing for Vietnamese balm remains unresolved. This study evaluated foliar 6-benzylaminopurine (6-BA; 0–25 ppm) on leaf development, physiology, and essential oil (EO) in Elsholtzia ciliata. Leaf traits, chlorophyll, soluble sugars, and antioxidant enzymes (POD, SOD) were measured; EO yield and composition were determined by GC–MS. Analyses included ANOVA, correlations, and PCA. All 6-BA doses enhanced the growth of leaves; 15 ppm was consistently the optimal dose. At 15 ppm, chlorophyll reached 2.54 mg/g FW and EO content rose to 3.27% (4.61-fold vs 0.71% control), accompanied by higher sugars and POD/SOD activities. GC–MS identified 26 constituents (95.88% of oil) at 15 ppm, with enrichment of oxygenated monoterpenes (neral+geranial 32.44%) and sesquiterpenes, notably (Z)-β-farnesene (21.43%). Correlations linked BA dose with leaf number (r=0.73), chlorophyll (r = 0.63), POD (r = 0.71), and SOD (r = 0.58); leaf size covaried with biomass, while EO showed weak direct correlation (r = 0.16). PCA (PC1 74.0%; PC2 8.7%) separated treatments along the BA gradient, with 15 ppm aligning with chlorophyll, sugar, and antioxidant vectors. Collectively, 15 ppm 6-BA maximized vegetative performance, physiological vigor, and EO yield/quality in E. ciliata, providing a practical regimen and a basis for mechanistic and agronomic optimization. Findings guide efficient, scalable horticultural management.