Relative ureide-N (%) = [4 x ureides/(4 x ureide
+ nitrate + amino-N)] x 100
Sicardi M, Izaguirre-Mayoral ML (1993) Ureide
content and growth of cowpea (Vigna unguiculata (L) Walp var.Tuy) plants as affected by Bradyrhizobium strains and inoculum position.
 Atkins, C.A., and Smith, P.M.C., 2000, "Ureide
synthesis in legume nodules.
An additional finely ground biomass subsample was analyzed for total ureide
content using the following procedure.
Soybean N2 fixation estimates, ureide
concentration, and yield responses to drought.
Sinclair and Serraj (1995) reported that warm-season species that accumulated high concentrations of ureides
(>200 mmol [L.sup.-1] xylem sap) were more drought-sensitive than species with <50 mmol [L.sup.-1] xylem sap or no ureide
Other nonnodulating genotypes have subsequently been isolated and one study showed that, in fact, the nonnodulating mutants contained much lower concentration of ureide
in developing pods (Matsumoto et al., 1977).
Inheritance studies using ureide
accumulation (Kueneman et al., 1984) and acetylene reduction (Chowdhury and Doto, 1981) screening techniques for promiscuous nodulation also obtained inconclusive results.
 RAU = (4 x ureide
cone.)/[(4 x ureide
conc.) + N[O.sup.-.sub.3;] conc.]
Recent studies have focused on ureide
accumulation and feedback on nodule activity as being crucial in influencing soybean [N.sub.2] fixation activity.
The involvement of Mn in the response to water deficit and the regulation of ureide
levels in leaves of some soybean cultivars has been documented in experiments in which increased Mn supply increased leaf ureide
degradation rates and ameliorated [N.sub.2] fixation sensitivity to water deficit (Purcell et al., 2000; Vadez et al., 2000).
(1999a) proposed that decreased demand for amino acids during water deficit resulted in asparagine accumulation, which has been shown to inhibit leaf ureide
breakdown (Lukaszewski et al., 1992).