POTASSIUM SUPPLY AND THE NUTRITIONAL STATUS OF JAMBU (ACMELLA OLERACEA) GROWN IN A HYDROPONIC SYSTEM

Abstract

Jambu (Acmella oleracea) is an Amazonian species of food and bioactive interest, mainly due to the presence of spilanthol. Potassium (K) participates in osmotic regulation, enzyme activation, and photoassimilate transport, influencing secondary metabolism. This study evaluated the effect of K supply on the nutritional status of plants grown in a nutrient film technique (NFT) hydroponic system and discussed its physiological implications for spilanthol biosynthesis. The experiment was conducted in a completely randomized design with five replicates, using a nutrient solution based on Furlani and different K concentrations. At 42 days after transplanting, leaves were collected, dried, ground, and subjected to macronutrient analysis. Increasing K raised leaf contents of N, P, and K, whereas higher doses reduced Ca and Mg, indicating ionic antagonism among competing cations. The concentration of 414 mg L⁻¹ showed the best nutritional balance, combining high N and K contents with smaller reductions in Ca and Mg. The results indicate that intermediate K doses may favor more suitable physiological conditions for the secondary metabolism of jambu, although spilanthol was not directly quantified in this study.