Supplementation with molybdenum optimises nitrate reductase activity during floral induction in mango trees

Floral induction in mango trees depends on nitrate to stimulate flowering, a process mediated by the enzyme nitrate reductase, whose activity is influenced by molybdenum (Mo). However, the interaction among these factors is still not fully understood. This study aimed to evaluate the effect of Mo supplementation on nitrate reductase activity and its relationship with mango flowering. The experiment was conducted over two growing trials (2022/2023 and 2023/2024) in two orchards of ‘Tommy Atkins’ mango trees located in Petrolina, Brazil. A randomised block design was used in a strip-split plot arrangement with a 4 × 2 factorial scheme: four Mo concentrations (0.000, 0.100, 0.225, and 0.375 g L⁻¹) and two calcium nitrate concentrations (standard and reduced). Foliar applications of Mo and calcium nitrate were carried out during the floral induction period. Nitrate reductase activity was positively correlated with global solar radiation. Overall, Mo supplementation improved nitrate reductase activity, the Mo-to-N ratio, flowering, and fruit yield. The concentration of 0.225 g L⁻¹ of Mo combined with a 0.475% reduction in the standard nitrate concentration was the most efficient treatment in promoting reproductive responses. The balanced application of Mo and nitrate proved to be an effective strategy to enhance nitrate assimilation and optimise the flowering and productivity of mango trees.