Ureide

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Ureide

 

(also known as ureid), any of the derivatives of urea [CO(NH2)2] resulting from the substitution of acyl (RCO) radicals for hydrogen atoms in the NH2 groups. Ureides are crystalline, high-melting compounds; the melting point of acetylurea (CH3CONHCONH2) is 218°C, while that of diacetylurea (CH3CONH)2CO is 153°C. Cyclic ureides are obtained from the reaction of urea with dibasic acids; for example, barbituric acid is obtained by reacting urea with malonic acid or malonic ester. The ureides of brome-substituted acids (bromisoval, carbromal) and cyclic ureides of the barbiturate type are used as sedatives.

References in periodicals archive ?
Although ureides were significantly reduced in the PlusN treatment of both the irrigated and nonirrigated environments, N concentration was not significantly different between N treatments in the irrigated environment (3.37 vs.
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.
The procedure for ureide analysis was as described by Young and Conway (1942) with minor modifications (Streeter, 1979).
Ureides and N[O.sup.-.sub.3] were extracted from petioles in 1.25 mL of 0.2 M NaOH at 100[degrees]C for 30 rain (de Silva et al., 1996).
There are at least two possible hypotheses based on degradation of ureides in the leaves as water deficits develop to explain the low ureide concentrations in Jackson.
Ureides were extracted from approximately 25 mg of dried nodule or leaf tissue in 1.25 mL of 0.2 M NaOH for 30 min at 100 [degrees] C, and concentrations were determined colorimetrically using the procedure of Young and Conway (1942) modified as previously described (de Silva et al., 1996).
It was hoped that in the Stage 1 screen that soybean germplasm might be identified which contained no petiole ureide because those legume species with high tolerance of [N.sub.2] fixation to soil drying appear not to transport ureides from the nodules (Sinclair and Serraj, 1995).
Ureides and amides as N sources for soybean seed growth and maturation in vitro.
The rapid decrease in ARA in response to allantoin indicates the inhibitory nature of ureides on nodule activity.
[plant.sup.-1] mg [nodule.sup.-1] Jackson 93 3.71 ** KS4895 158 ** 2.18 avg ([dagger]) 132ns 3.40 * avg 119 2.50 Shoot ureide Acetylene reduction Cultivar Conc.
Role of amides, amino acids, and ureides, in the nutrition of developing soybean seeds.