[en] The effect of ultraviolet irradiation and temperature on the qualitative and quantitative composition of some physiological groups of microorganisms from soybean (Glycine hispida Max.) rhizosphere has been studied. It was established that the total amount of the plant's microflora significantly changed under the influence of these factors. This effect was reflected on quantitative variations of particular taxonomic groups of microorganisms. (author)

No abstract available

[en] For the detailed analysis of a canopy structure, e.g., solar radiation environment, it is necessary to obtain spatial data related to the leaf position in a canopy. We approximated a leaflet shape into an ellipsoid because, if it is possible, necessary data for determining the spatial position of each leaflet can be obtained by using the manipulator technique, which is used to measure a certain point in space accurately. The coincidence of a soybean leaflet area, which was measured using an area meter, and an ellipsoid area, which was obtained by approximating the maximum width and maximum length of a leaflet to the short axis and long axis of an ellipsoid, respectively, was ascertained in five cultivars of the soybean plant. Then, for a soybean population, the spatial factors of each leaflet were measured with a manipulator, i.e., the spatial position of each leaflet was determined at four points (in three-dimensional spaces) two for the maximum width and two for the maximum length of a leaflet. These data were used for the computer simulation of the canopy structure including the leaf area density in each layer with inclination angles of leaflets and the sunlit area. (author)

[en] Brown nitrogen-containing polymers are prepared by auto-oxidation at pH 7.9 from an equimolar mixture of catechol and glycine. Strict control of the experimental conditions yields products of constant composition, and affords a basis for the selective preparation of three polymers labelled with ¹⁴C on the atoms C₁ and C₂ of the glycine and on the catechol ring. These polymers have a mean molecular size smaller than that of humic acids extracted from neutral soils but their structure resembles more that of hydrolytic residues from eutrophic humic acids and melanins. Their stoichiometric ratio is 2 moles of glycine to 7 moles of catechol. They are not completely homogeneous and contain two groups of substances: the first and more abundant group is larger and permits optimum stabilization of the glycine in highly resonant structures; the second group remains more sensitive to hydrolytic treatment and biodegradation; they are characterized by partial fission of the aromatic rings during synthesis, which is responsible for the formation of the ring-deriving-COOH groups. The biodegradation of these polymers in a neutral mull reveals two successive stages: (a) an initial stage lasting five days, during which the ring-deriving-COOH groups are actively decarboxylated, whereas the glycine bound to the less stable fraction is degraded perferentially and then metabolized in the unextractable microbial substances (microbial humin). The non-amino residues of the polymers then have a depressant effect on soil respiration, which disappears only when their transformation by degradation or reaction with the soil organic compounds occurs; (b) A second stage, characterized by very slow mineralization and affecting almost exclusively the more stable polymers incorporated into the humin by physico-chemical insolubilization. There is then no further preferential degradiation of the glycine, the stability of which equals that of the ring-deriving carbon compounds of aromatic origin. The study shows that the incorporation of amino-acid residues into polymers originating from quinone structures represents an important form of storage for organic soil nitrogen. (author)

[en] Soybeans (Glycine max (L.) Merr.) have a high N requirement which is fulfilled by soil N uptake and N₂-fixation. This study was concerned with the effects of past yield selection on N₂-fixation in soybeans. The soybean cultivars, ‘Lincoln’, ‘Shelby’, and ‘Williams’, which represent successive improvements in the ‘Lincoln’ germplasm, and a non-nodulating control were planted in a soil containing ¹⁵N labelled organic matter. Two replications occurred on soil previously cropped to alfalfa and two on soil previously cropped to soybeans. Plants were harvested at five growth stages and leaf area, plant weight, total N, and atom percent ¹⁵N were determined. Mature grain was harvested and yield components were also determined, as well as the total N and ¹⁵N content. Cultivar differences in total dry matter were only evident at physiological maturity, when Williams contained the greatest dry matter. Williams exhibited the longest period of seed formation and seed fill and also had the highest grain yield which resulted from a larger weight per seed. The N content of the cultivars did not vary until physiological maturity when Williams contained the highest percent N. The quantity of N fixed at physiological maturity was highest for Williams and lowest for Lincoln. Fixed N contained in the harvested grain was greater for Williams than for the other two cultivars. The fraction of the total plant N derived from fixation was not greatly affected by cultivar and all cultivars acquired an average of 50% of their total N through N₂-fixation. Previous cropping history greatly affected the quantity of N fixed and the fraction of the total plant N derived from fixation. Soybeans following soybeans were more dependent upon N₂-fixation than soybeans following alfalfa with the former deriving 65% of the total plant N from fixation and the latter only 32%. These soybean cultivars apparently utilized soil N first and then used N₂-fixation to satisfy their N requirement. The past selection for higher yield has resulted in soybean cultivars with improved capacities to fix atmospheric N₂ and an improved ability to take up available soil N

No abstract available

[en] Multiple weed species in the field combine to cause yield losses and can be described using one of several empirical models. Field studies were conducted to compare observed corn yield loss caused by common sunflower and shattercane populations with predicted yield losses modeled using a multiple species rectangular hyperbola model, an additive model, or the yield loss model in the decision support system, WeedSOFT, and to derive competitive indices for common sunflower and shattercane. Common sunflower and shattercane emerged with corn and selected densities established in field experiments at Scandia and Rossville, KS, between 2000 and 2002. The multiple species rectangular hyperbola model fit pooled data from three of five location–years with a predicted maximum corn yield loss of 60%. Initial slope parameter estimate for common sunflower was 49.2 and 4.2% for shattercane. A ratio of these estimates indicated that common sunflower was 11 times more competitive than shattercane. When common sunflower was assigned a competitive index (CI) value of 10, shattercane CI was 0.9. Predicted yield losses modeled for separate common sunflower or shattercane populations were additive when compared with observed yield losses caused by low-density mixed populations of common sunflower (0 to 0.5 plants m⁻²) and shattercane (0 to 4 plants m⁻²). However, a ratio of estimates of these models indicated that common sunflower was only four times as competitive as shattercane, with a CI of 2.5 for shattercane. The yield loss model in WeedSOFT underpredicted the same corn losses by 7.5%. Clearly, both the CI for shattercane and the yield loss model in WeedSOFT need to be reevaluated, and the multiple species rectangular hyperbola model is proposed. (author)

No abstract available

[en] We have demonstrated that the chiral aldehyde 1 catalyzes the stereoselective decarboxylation of [MAM-H]"-. The stereoselectivity is maximum in monoanionic form of MAM. The D-form-favor in the decarboxylation may be explained by the removal of the protonated carboxylate group and protonation at the same site. Aminomalonic acid (AM-H_2) is a biological intermediate appearing in the conversion course of serine to glycine. Amino-malonic decarboxylases, enzymes that catalyze decarboxylation of aminomalonic acid, have been found in many living systems. Serine hydroxymethyltransferase stereospecifically decarboxylates 2-amino-2-methyl-malonic acid (MAM-H_2) to produce D-alanine. Although stereoselective decarboxylation is a century old theme, the interest on it is growing recently owing to the development of chiral technology. Chemical approaches using metal complexes and cinchonine derivatives have been developed for stereospecific decarboxylation of MAM

[en] Nanoparticle (NP) surface coatings are known to influence the toxicity of engineered nanomaterials. This work examines the effect of glycine functionalization on silica NPs and investigates changes in viability and developmental defects in the organs of zebrafish embryos upon exposure. Silica NPs and glycine-functionalized silica NPs are synthesized and characterized. Exposure of zebrafish embryos to glycine-silica NPs affects the mortality percentage in a similar manner to soluble glycine. Developmental defects are observed in embryos exposed to soluble glycine, glycine-silica NPs, or silica NPs in comparison with the unexposed embryos. The damage is localized in the brain, heart, and liver of zebrafish embryos. These observations suggest a complex mechanism of toxicity, with glycine maintaining its toxic activity even when covalently bound on silica surface. Our results illustrate that surface modification of non-lethal particles can create different toxicity outcomes in the organs of exposed zebrafish embryos. - Highlights: • Modification of silica nanoparticles with glycine impacts the toxicity profile of silica. • Free and bound glycine induces developmental abnormalities in embryonic zebrafish. • Developmental defects in brain, liver and cardiovascular system are assessed.