Influence of potassium nutrition on photosynthetic performance and antioxidant activity in cacao (Theobroma cacao L.) clones: Evidence from controlled-environment trials

Cacao (Theobroma cacao) cultivation is a strategic activity for rural development in Nariño, Colombia, offering sustainable livelihood opportunities in regions affected by social conflict and agroecological constraints. However, climate change and soil nutrient depletion increasingly challenge crop productivity and bean quality. This study aimed to evaluate the physiological and biochemical responses of the CCN51 cacao clone under controlled environmental conditions and different potassium (K) fertilization levels, to better understand adaptive mechanisms relevant to crop management in vulnerable systems. The trial was conducted in a greenhouse over six months, applying potassium at concentrations of 200 and 400 mg/kg. Photosynthetic performance was monitored using the Multispec 2.0 device, and biochemical responses were assessed through the activity of antioxidant enzymes, including glutathione peroxidase and ascorbate peroxidase. Results indicated that higher potassium doses enhanced biomass accumulation and maintained photosynthetic efficiency, while intermediate doses activated compensatory mechanisms that supported plant development. Furthermore, potassium application positively regulated antioxidant enzymatic activity, suggesting its essential role in physiological stability and redox balance. These findings provide valuable insights for improving cacao productivity and resilience through targeted fertilization strategies adapted to the specific agroecological conditions of regions such as Nariño.