Effect of Nitrogen Fertilizer Rate and Harvest Season on Forage Yield, Quality, and Macronutrient Concentrations in Midland Bermuda Grass
Bermuda grass [Cynodon dactylon (L.) Pers.] is a major forage for grazing and hay production in the southern United States. The objectives of this study were to determine effects of nitrogen (N) fertilization rate (0, 112, 224, 336, and 448 kg ha−1), split spring and summer applications of N at the 224 and 448 kg ha−1 rates, and harvest periods (spring and summer) on forage yield, crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), total digestible nutrients (TDN), and concentrations of phosphorus (P), potassium (K), magnesium (Mg), and calcium (Ca in Midland Bermuda grass. Data were collected from 2002 to 2008 as part of an ongoing, long-term soil fertility experiment in southern Oklahoma. Repeated measures analysis of these long-term data showed that forage yield responses to N rate varied with year and harvest time with up to 2.5-fold yield differences among years. Nitrogen fertilization increased CP, TDN, and macronutrient P and Mg and decreased ADF and NDF. Crude protein was increased by ≥50%, and ADF and NDF dropped by up to 25% with the greatest N rate. In general, split N applications did not affect forage yield but produced low-quality forage compared to single N application in spring. Split application of 448 kg N ha−1 gave forage with CP, TDN, ADF, and NDF similar to the Bermuda grass receiving 336 or 448 kg N ha−1 as a single application. Spring forage had better forage quality than summer harvests. While N fertilization increased forage Mg and P concentrations by more than 50% during both spring and summer, it had no effect or slight increased K and Ca concentrations. In the southern Great Plains, despite the weather-dependent variability in forage yield of Bermuda grass, N application increase forage quality.
Cytogenetic and molecular responses of ammonium sulphate application for tolerance to extreme temperatures in Vicia faba L.
Effects of ammonium sulphate [(NH4)2SO4] on mitosis, cell cycle and chromosomes in Vicia faba L. seeds exposed to extreme temperatures were investigated using flowcytometric and cytogenetic analysis. Seeds germinated at high and low temperatures showed a significant decrease in mitotic index as compared to those of optimum temperature conditions. Application of 50 and 1000 μM (NH4)2SO4 were successful in alleviating the negative effects of low and high temperature on mitotic activity, respectively. 50 μM (NH4)2SO4 showed the most positive effect on cell cycle at the extreme temperatures. This concentration increased the cell division removing or decreasing the negative effects of temperature stress. Namely, the highest G2/M and S phase percentages under stress conditions were obtained with application of 50 μM (NH4)2SO4. Chromosomal aberrations were not observed in cells of seeds germinated in distilled water and also at any temperatures. However, the frequency of chromosomal aberrations increased significantly by increasing (NH4)2SO4 concentration. The highest aberration frequency in all temperature degree tested was found at 1000 μM (NH4)2SO4 concentration.
Hapten inhibition of passive antidextran dextran anaphylaxis in guinea pigs. Role of molecular size in anaphylactogenicity and precipitability of dextran fractions.
High titred antidextran antisera have been raised in rabbits by prolonged immunization with soluble conjugates between isomaltose oligosaccharides or dextran mw 4,400 and bovine serum albumin in complete Freund’s adjuvant. Guinea pigs sensitized with such antisera exhibited anaphylactic shock on i.v. challenge with fractions of hydrolyzed B512 dextran. The severity of anaphylaxis depended on the amount of sensitizing antibody and the dose and molecular size of the challenging dextran fraction. In maximally sensitized animals, fractions of mw 3,600 or larger were anaphylactogenic and smaller molecular size fractions were nonanaphylactogenic. In submaximally sensitized animals, dextran fractions of mw 10,500 or less were foundnonanaphylactogenic. In addition, nonanaphylactogenic dextran fractions produced desensitization, i.e. protection from anaphylaxis due to subsequent or simultaneous injection of more high molecular and anaphylactogenic dextran fractions. When the molar ratio in a mixture of nonanaphylactogenic/anaphylactogenic fractions was about 7.6, protection was complete with reduction of mortality from 100 to 0%. A molar ratio of 1.9, corresponding to a 13-percent by weight admixture of nonanaphylactogenic dextran, still significantly reduced mortality from 100 to 50%. From the ability to form precipitates with antidextrans and to elicit anaphylaxis in sensitized guinea pigs, and from the absence of these properties, the approximate molecular size range of bivalent and monovalent dextran B512 fractions was found to correspond to mw 3,600 and mw 1,430, respectively. The practical applicability of hapten inhibition is discussed.