Ureide accumulation in faba bean (Vicia faba, L.)

• Other Authors: Bueckert, Rosalind
• Language: English
• Published: 2014
• Subjects: Ureides; Faba bean; Abiotic stress; Nitrogen fixation; Allantoin; Allantoate
• Online Access: http://hdl.handle.net/10388/ETD-2014-08-1702

Faba bean (Vicia faba L.) is a cool season crop that uses symbiotic biological nitrogen fixation to obtain atmospheric nitrogen (N), a limiting macronutrient, for growth and maintenance of the plant. Most cool season legumes like faba bean transport N from the nodules as amides, which are metabolized in destination tissues. Ureide metabolism is a catabolic process that produces N rich compounds from purine rings. Many warm season legumes such as soybean and common bean produce ureides (allantoin and allantoate) in their root nodules and then use these molecules to transport fixed nitrogen from root to shoot. Non-ureide exporting plants such as faba bean also produce ureides in normal purine recycling whereby these compounds may play a role in response to abiotic stress. This research aims to examine possible differences in ureide metabolism across genotypes and to assess the role of ureides in response to water limitation. In field grown faba bean, total ureides were found in highest concentrations in leaf tissue, followed by reproductive parts, stems, and nodules, but were not found to differ significantly among genotypes. Ureide concentrations varied throughout the growing season, decreasing over time as the plants reached physiological maturity. A water limitation experiment of faba bean grown in a controlled environment showed that faba bean accumulated the ureides allantoin and allantoate after six to eight days of water limitation when all data were pooled. However, no consistent trend was observed comparing results by genotype, and inoculated versus non-inoculated plants. Overall, results indicate that faba bean likely does not use ureides to transport symbiotically fixed N and that ureide accumulation in field grown plants is most likely in response to abiotic stress or remobilization of purine N from senescing tissues.