Exogenous benzyladenine reinforces the antioxidant activity, phytochemical content, and macronutrients of Tagetes erecta plants

Abstract

Growth regulators have become an effective tool for enhancing the cultivation of medicinal and aromatic plants by promoting vegetative development and increasing the accumulation of bioactive metabolites. Benzyladenine (BA), a synthetic cytokinin, is widely recognized for its ability to influence growth and secondary metabolism in ornamental species; however, dose response evaluations under open field conditions remain limited for Tagetes erecta. This study examined the effects of foliar BA applications at 0, 50, 75, and 100 ppm, applied weekly over three intervals, on vegetative growth, pigment composition, antioxidant-related metabolites, and macronutrient status. BA treatments significantly improved all measured parameters relative to untreated plants, with responses showing a clear concentration dependent trend. The 100 ppm treatment produced the most pronounced enhancements, yielding maximum vegetative growth (72.133 cm height, 177.80 g fresh weight, 74.26 g dry weight), highest pigment levels (8.35 mg/100 g FW chlorophyll a, 5.88 mg/100 g FW chlorophyll b, 5.12 mg/100 g FW carotenoids), improved mineral content (3.15% nitrogen, 0.454% phosphorus, 2.92% potassium), and elevated antioxidant properties (25.844% antioxidant activity, 94.2 mg/100 g FW total phenols, 2.884 mg/100 g FW total flavonoids). These findings demonstrate that BA, particularly at 100 ppm, effectively enhances growth performance and secondary metabolite accumulation in T. erecta, providing field-based evidence for the role of cytokinins in optimizing the agronomic and phytochemical potential of this economically important ornamental species.