Water deficit alters metabolism, source–sink balance, and metabolomic profile in bean (Phaseolus vulgaris) pericarp

• Pericarp adapts to maintain photoassimilate flow under water deficit. • Water deficit altered aldehydes, esters, and dienes (metabolomics). • Sucrose synthase and vacuolar invertase rose under water deficit. • Pericarp carbohydrate shifts help protect developing sink tissues. This study investigates the impact of water deficit on the physiological and metabolic responses of the common bean ( Phaseolus vulgaris L.), focusing on the pericarp, a key tissue for seed development. Exposure to water deficit reduced total seed yield by 62%, primarily due to a 52% decrease in pod number, while seed number per pod and individual seed weight remained largely unaffected. Despite declining soil moisture, glucose and fructose concentrations in seeds and leaves remained stable, whereas glucose in the pericarp increased significantly 15 days after the onset of water deficit, and sucrose levels rose at 30 days. These changes were accompanied by increased activity of sucrose-metabolizing enzymes, including sucrose synthase (∼30% increase) and vacuolar invertase (∼40% increase), while cell wall invertase activity decreased (∼60%). Metabolomic profiling revealed substantial shifts in the pericarp's chemical composition, notably in aldehydes, esters, and dienes, indicating a metabolic adjustment that supports seed development under water deficit. These findings provide new insights into the mechanisms of water deficit tolerance in common bean and identify potential targets for improving stress resilience in this crop.