Mineral and Carbon Metabolic Adjustments in Nodules of Symbiotically Grown Faba Bean (Vicia faba L.) Varieties in Response to Organic Phosphorus Supplementation

Phosphorus (P) is a major limiting factor for legume and symbiotic nitrogen fixation (SNF). Although overall adaptations of legumes to P supplementation have been extensively studied in connection with inorganic P, little information is currently available regarding nodulation or SNF responses to organic P (Po) in hydroponics. We investigated the mineral and carbon metabolism of Po-induced nodules of two contrasting faba bean varieties grown hydroponically under inorganic P (Pi), viz., in P-deficient (2 mu M KH2PO4, -Pi), sufficient-P (200 mu M KH2PO4, +Pi), and phytic acid (200 mu M, Po) conditions, and were inoculated with Rhizobium leguminosarum bv. viciae 3841 and grown for 30 days. The results consistently reveal similar growth and biomass partitioning patterns between +Pi and Po, with both varying substantially from -Pi. In comparison, +Pi and Po observed equivalent accumulations of overall elemental P concentrations, with both increasing by 114 and 119%, respectively, relative to -Pi. A principal component analysis on metabolites showed a clear separation of the -Pi treatment from the others, with +Pi and Po correlating closely together, highlighting the nonsignificant differences between them. Additionally, the delta N-15 abundance of shoots, roots, and nodules was not significantly different between treatments and varieties and exhibited negative delta N-15 signatures for all tissues. Our study provides a novel perspective on mineral and carbon metabolism and their regulation of the growth, functioning, and reprogramming of nodules upon phytate supply.

Automated summary

This study investigates the mineral and carbon metabolism of faba bean nodules under different phosphate conditions. The results show similar growth patterns and biomass partitioning between phosphate and phytate treatments, both differing substantially from the phosphate-deficient treatment. Additionally, the overall elemental phosphorus concentrations in both phosphate and phytate treatments significantly increase compared to the phosphate-deficient treatment. Metabolite analysis reveals no significant differences between phosphate and phytate treatments.