Elucidating the role of Kelpak® on the growth, phytohormone composition, and phenolic acids in macronutrient-stressed Ceratotheca triloba

We evaluated the role of Kelpak® on growth, nutritional content, phytohormones, and phenolic acids in the angiosperm Ceratotheca triloba (Bernh.) Hook.f. grown under macronutrient-deficient conditions. Seeds were germinated in the greenhouse and established seedlings were treated with 50% Hoagland’s solution (50% HS) or nutrient-deficient solutions lacking one of the following: nitrogen (-N), phosphorus (-P), potassium (-K), which were either treated with or without Kelpak® (control). After 4 months of growth, macronutrient deficiency severely reduced growth and nutritional composition in plants. Nevertheless, the detrimental effects of insufficient macronutrient supply on growth were ameliorated with the application of Kelpak®, with a fourfold (-N), threefold (-P), and twofold (-K) increase in leaf and root fresh weight. Mineral and carbohydrate levels increased in plants deprived of N and P when Kelpak® was applied in the different soils. Macronutrient stress (N, P, K) increased phytohormone production in C. triloba more than in 50% HS-treated plants. The phytohormone content in macronutrient-deficient leaves was further enhanced with the application of Kelpak®. On the contrary, application of Kelpak® suppressed the production of phenolic acids in 50% HS, -N, and -K-treated plants when compared to the control treatments. The interaction between macronutrient deficiency and Kelpak® application played an important role in the regulation of phytohormone and phenolic acid concentration in C. triloba. The current findings demonstrated the potential of Kelpak® as an efficient biostimulant that enhances nutrient uptake for improved growth and biochemicals in C. triloba under macronutrient stress condition.