Phenological stage influences how white lupin (Lupinus albus) root exudate metabolites respond to phosphorus supply

The composition and quantity of root exudates are strongly influenced by physiological and environmental conditions, reflecting dynamic changes in plant metabolism. Although many studies report that root exudate metabolite profiles vary with plant phenology, few have disentangled the effects of phenological stage from those of nutrient availability. We collected root exudates from white lupin (Lupinus albus) grown in a fine phosphorus (P) gradient (5, 10, 20, 30 and 50 {micro}M P) in hydroponics at three developmental stages, performed untargeted metabolomics using GC-MS, and measured 10 above and belowground traits. Our results show that plant phenological stage exerts a stronger influence on exudate metabolomic profiles than variation in P supply. During leaf development, exudates were dominated by metabolites associated with carbon metabolism, whereas flowering was characterized by compounds related to secondary metabolism and cell wall turnover. Phosphorus influenced exudate profiles only at the flowering stage, with distinct profiles observed at 5 and 10 {micro}M P compared with 20-50 {micro}M P. These findings provide new insights into the temporal regulation of root exudation and demonstrate that plant developmental stage is a primary determinant of metabolic responses to phosphorus availability and, potentially, rhizosphere functioning under nutrient limitation. HighlightRoot exudate quantity and composition in white lupin is shaped more by plant phenological stage than phosphorus supply, with phosphorus effects emerging only during flowering.