Nitrogen is the most limiting macronutrient for growth, photochemical performance and stomatal conductance in Agave spp

Macronutrient availability is a major constraint for Agave cultivation in semi-arid regions, yet its effects on growth, nutrient balance, and physiological performance remain poorly understood. In a 317-day greenhouse pot experiment, this study evaluated the effects of nitrogen (-N), potassium (-K), calcium (-Ca), and magnesium (-Mg) omission on biomass production, nutrient accumulation, nutrient use efficiency, photochemical performance, and stomatal conductance in Agave sp. IAC4 and A. sisalana. Macronutrient omission impaired growth and nutrient homeostasis in both genotypes, with -N causing the strongest effects and reducing total biomass by up to 56%, particularly in A. sisalana. Nutrient limitation also altered stomatal conductance and photochemical performance, with maximum electron transport rate decreasing by up to 51% under -N. A. sisalana was more sensitive to nutrient limitation than IAC4, showing greater reductions in biomass, nutrient accumulation, and physiological performance. Overall, N was the most limiting macronutrient among those evaluated, followed by K and Ca, whereas Mg had comparatively smaller effects. These findings demonstrate that macronutrient availability strongly influences the coordination of growth, nutrient homeostasis, and physiology in Agave, while revealing substantial genotype-dependent responses under nutritional limiting conditions.