Vergleich von Nitrat- und Amino-N-Schnelltest zur Charakterisierung des Stickstoff-Versorgungsgrades von Winterweizen

Comparison of the rapid tests for nitrate and amino-N for evaluating the N-status of winter wheat Nitrogen fertilizer trials with winter wheat were conducted in 1985 and 1986 to compare the efficacy of the rapid test for nitrate (in the stem base) and a newly developed rapid test for amino-N (in fully expanded green leaves) for evaluating the N-status of plants. In addition, the influence of weather conditions on the results given by both tests when using ammonium nitrate (NH₄NO₃ + CaCO₃) (AN) and urea-ammonium nitrate solution (UAN), was evaluated to determine wether the rapid test for amino-N gives more accurate information on the N-status of winter wheat than the rapid test for nitrate. The results show that the rapid test for nitrate is suitable to characterize the N-status of winter wheat when nitrogen is predominantly taken up by roots as nitrate. This is normaly the case when plants are fertilized with the salt form of nitrogen, als well as with liquid fertilizer, such as UAN applied through tubes in the soil, as for fertilization of winter wheat at later growing stages. However, during dry weather (1986 field trial) UAN application on leaves at shooting and ear emergence can result in high nitrogen uptake by leaves, causing an underestimation of plant N-status by the rapid test for nitrate, and thus, subsequent excess N-fertilizer application may be recommended (order of magnitude: 20 kg N/ha). Under these conditions the rapid test for amino-N in leaves (pressed sap) is a more accurate test for estimation of plant N-status because it determines glutamine and amino acids, the most important storage forms of reduced nitrogen in plants. When UAN fertilizer on leaves is washed off by rain (1985 field trial), crop N-fertilizer requirements predicted by both tests are comparable. If storage of nitrate in the stem base occurs, due, for example to low radiation intensity during spring (lower nitrate reduction), with the rapid test for amino-N an underestimation of plant N-status can be obtained.     

Microspore culture of white cabbage, Brassica oleracea var. capitata L.: Genetic improvement of non-responsive cultivars and effect of genome doubling agents

For the efficient application of haploid induction procedures in cabbage breeding, a sufficient number of regenerants should be achieved in a broad spectrum of genotypes. However, the majority of genotypes are somewhat recalcitrant. The efficiency of microspore culture was tested by crossing a responsive (28.7 embryos per Petri dish) and a non- responsive (0.1 embryo) cabbage cultivar. The embryo yield of one progeny was intermediate (18.9) while two were superior to the best parent cultivar (52.9 and 64.0 embryos). Thus, genes for haploid embryogenesis, present in responsive lines, can be effectively transmitted to responsive × non-responsive hybrids. Abscisic acid-induced desiccation of embryos was used for the efficient regeneration of plants. High germination percentages (54.7-70.6%) followed by normal plantlet development were achieved. Spontaneous genome doubling measured at the plantlet stage differed markedly in untreated genotypes. The percentage of diploids ranged from 21 to 67%. The effects of two antimitotic drugs applied to freshly isolated microspores were determined in two experiments. In the first experiment, trifluralin (0.5 and 1.0 mg:l) had no effect on embryo induction while oryzalin partly (0.125-0.25mg/l) or completely (0.5.mg/l) inhibited the formation of embryos. In the second experiment, higher concentrations of trifluralin increased the proportion of diploidized plants. Application of anti-mitotic drugs to microspores did generally not improve the overall production of haploid plants, which was higher in an untreated control.     

Photosynthesis,chlorophyll fluorescence,and water relations in young sugar beet plants as affected by sulfur supply

The effect of different concentrations of sulfur (1 and 3 mM) and interruption of sulfur (S) supply for 25 days on the photosynthesis and leaf water relations in young sugar beet plants (Beta vulgaris L.) was studied in water culture, under greenhouse conditions. Interruption of S‐supply significantly reduced the content of sulfur, chlorophylls a+b and carotenoids, leaf area, density of stomatal and epidermal cells, transpiration rate and leaf water potential, while it increased the free proline content and stomatal diffusion resistance. An increase in S concentration in the nutrient medium from 1 to 3 mM did not significantly affect the tested parameters, except for an increase in leaf S content and a decrease of leaf water potential. Sulfur deficiency caused a pronounced decrease of the rate and quantum yield of photosynthetic oxygen evolution under non‐photorespiratory conditions. This was partly the result of the diminished photochemical efficiency of photosystem II reaction centers. Less efficient excitation of PSII reaction centers is most probably the consequence of higher thermal energy dissipation in the reaction centers of S‐starved plants. These data support that S nutrition is one of the factors regulating plant photosynthesis.     

Influence of dietary quercetin on glutathione redox status in mice

Flavonoids such as quercetin have been shown to serve as a protective defense against oxidative damage in vivo. However, the bioavailability of quercetin depends on the food source and type of glycosidic moiety linked to the molecule. In this study, mice were fed 1 mg/day quercetin in the form of quercetin aglycone, rutin, apple, or onion, and reduced glutathione (GSH), oxidized glutathione (GSSG), and protein-GSH mixed disulfides were determined to investigate the influence of dietary quercetin on the GSH redox status in metabolically active tissues, mitochondria, and plasma of mice. All quercetin treatment groups produced increases in the GSH:GSSG ratio and decreases in mixed disulfide levels in hepatic tissue. Cardiac tissue did not change in response to dietary quercetin; however, cardiac mitochondria demonstrated a reduction in the GSH:GSSG ratio and an increase in protein mixed disulfide levels. No significant changes were observed in the plasma GSH:GSSG ratio, but mixed disulfide levels were decreased for all of the diets. The changes in plasma redox status did not parallel the changes in the tissues. Onion fed mice demonstrated the greatest increases in GSH:GSSG ratios and the greatest decreases in protein mixed disulfide levels of all diets compared. For all treatment groups, increases in the GSH:GSSG ratios corresponded with decreases in protein mixed disulfide levels. The results of this study indicate that quercetin influences GSH:GSSG ratios and protein thiolation in a tissue-specific manner and that these effects are dependent on food source and bioavailability.     

Sandwich immunoassays for the determination of peanut and hazelnut traces in foods

People suffering from food allergies are dependent on accurate food labeling, as an avoidance diet is the only effective countermeasure. Even a small amount of allergenic protein can trigger severe reactions in highly sensitized patients. Therefore, sensitive and reliable tests are needed to detect potential cross-contamination. In this paper two fast sandwich immunoassays are described for the determination of peanut (Arachis hypogaea) and hazelnut (Corylus avellana) traces in complex food matrices. Mouse monoclonal antibodies were used as capture antibodies, and labeled rabbit polyclonal antibodies were used as detection antibodies in both assays. The assay time was 30 min in total, and cross-reactivities against a variety of fruits and seeds were found to be in the low 10(-4)% (ppm) level or in some cases not detectable. The recoveries in all tested food matrices ranged from 86 to 127%, and the limits of detection were in the range of 0.2-1.2 mg/kg (ppm) in food for both peanut and hazelnut, respectively.     

Der Einsatz von Kationenaustauscherharzen zur Charakterisierung verfügbarer Kationen aus natürlich gelagerten Bodenproben

Investigation of cation release of undisturbed soil columns via cation exchange resins Undisturbed soil columns were investigated with cation exchange resins. Similar to roots there is an exchange of H⁺ and cations. The ability for release of cations by molecular diffusion is decreasing with time, so that an asymptotic approximation to a final value occurs. A part of the protons is buffered, for example by aluminium-hydroxides. Samples rich in organic carbon show different graphs for iron and manganese which is probably due to microbial reduction processes.     

Changes in soil carbon and crop yield over 60 years in the Zurich Organic Fertilization Experiment,following land‐use change from grassland to cropland

Changes in land‐use and agricultural management affect soil organic C (SOC) storage and soil fertility. Grassland to cropland conversion is often accompanied by SOC losses. However, fertilization, crop rotation, and crop residue management can offset some SOC losses or even convert arable soils into C sinks. This paper presents the first assessment of changes in SOC stocks and crop yields in a 60‐year field trial, the Zurich Organic Fertilization Experiment A493 (ZOFE) in Switzerland. The experiment comprises 12 treatments with different organic, inorganic and combined fertilization regimes. Since conversion to arable land use in 1949, all treatments have lost SOC at annual rates of 0.10–0.25 t C ha^?1, with estimated mean annual C inputs from organic fertilizers and aboveground and belowground plant residues of 0.6–2.4 t C ha^?1. In all treatments, SOC losses are still in progress, indicating that a new equilibrium has not yet been reached. Crop yields have responded sensitively to advances in plant breeding and in fertilization. However, in ZOFE high yields can only be ensured when mineral fertilizer is applied at rates typical for modern agriculture, with yields of main crops (winter wheat, maize, potatoes, clover‐grass ley) decreasing by 25–50% when manure without additional mineral fertilizer is applied. ZOFE shows that land‐use change from non‐intensively managed grassland to cropland leads to soil C losses of 15–40%, even in rotations including legumes and intercrops, improved agricultural management and organic fertilizer application.     

Organic compounds and heavy metals in the atmosphere of the city of Caracas,Venezueala — II: Atmospheric deposition

Aliphatic and aromatic hydrocarbons, fatty acids and heavy metals (Pb, Cu, Ni, Zn, Fe and Cd) were analyzed in bulk deposition samples at two locations within the metropolitan area of Caracas, Venezuela. One of the sampling sites was located in the center (urban site, 1), while the other was in the outkirts of the city (rural site, 4). In general, a higher flux was observed for the deposition of pollutants at site 1 than at site 4. These fluxes showed relatively large short-term variations, while the long-term integrated deposition was found to be relatively constant throughout the sampling period. Wet deposition did not affect the flux of most of the pollutants studied, with the exception of Pb and the fatty acids of an anthropogenic origin.