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United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

1997

Articles 1 - 11 of 11

Full-Text Articles in Plant Sciences

Growing Degree-Days: One Equation, Two Interpretations, Gregory S. Mcmaster, Wallace Wilhelm Nov 1997

Growing Degree-Days: One Equation, Two Interpretations, Gregory S. Mcmaster, Wallace Wilhelm

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Heat units, expressed in growing degree-days (GDD), are frequently used to describe the timing of biological processes. The basic equation used is GDD = [(TMAX + TMIN)/2] - TBASE where TMAX and TMIN are daily maximum and minimum air temperature, respectively, and TBASE is the base temperature. Two methods of interpreting this equation for calculating GDD are: (1) if the daily mean temperature is less than the base, it is set equal to the base temperature, or (2) if TMAX or TMIN < TBASE they are reset equal to T …

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Conservation Compliance Credit For Winter Wheat Fall Biomass Production And Implications For Grain Yield, Gregory S. Mcmaster, Wallace Wilhelm Sep 1997

Conservation Compliance Credit For Winter Wheat Fall Biomass Production And Implications For Grain Yield, Gregory S. Mcmaster, Wallace Wilhelm

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Producers participating in federal farm and conservation programs must reduce potential erodibility below certain thresholds on lands classified as highly erodible. The Natural Resource Conservation Service (NRCS) will credit producer s in Colorado for the quantity of green winter wheat (Triticum aestivum L.) biomass at the beginning of the winter period towards compliance in reducing erosion. Unfortunately, few data exist on fall winter wheat biomass production and fall production varies widely based on many site-specific factors at planting and during the fall, and can be expensive to document. To address these problems, a crop simulation model called SHOOTGRO …

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Pathogenicity Of Escherichia Coli O157:H7 In The Intestines Of Neonatal Calves, Evelyn A. Dean-Nystrom, Brad T. Bosworth, William C. Cray Jr., Harley W. Moon May 1997

Pathogenicity Of Escherichia Coli O157:H7 In The Intestines Of Neonatal Calves, Evelyn A. Dean-Nystrom, Brad T. Bosworth, William C. Cray Jr., Harley W. Moon

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Cattle are an important reservoir of Shiga toxin-producing enterohemorrhagic Escherichia coli (EHEC) O157:H7 strains, foodborne pathogens that cause hemorrhagic colitis and hemolytic uremic syndrome in humans. EHEC O157:H7 strains are not pathogenic in calves >3 weeks old. Our objective was to determine if EHEC O157:H7 strains are pathogenic in neonatal calves. Calves(A/E) lesions in both the large and small intestines by 18 h postinoculation. The severity of diarrhea and inflammation, and also the frequency and extent of A/E lesions, increased by 3 days postinoculation. We conclude that EHEC O157:H7 strains are pathogenic in neonatal calves. The neonatal calf model is …

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Selenium Speciation Of Soil/ Sediment Determined With Sequential Extractions And Hydride Generation Atomic Absorption Spectrophotometry, Dean A. Martens, Donald L. Suarez Jan 1997

Selenium Speciation Of Soil/ Sediment Determined With Sequential Extractions And Hydride Generation Atomic Absorption Spectrophotometry, Dean A. Martens, Donald L. Suarez

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Understanding the speciation of the multioxidation states of selenium is vital to predicting the mineralization, mobilization, and toxicity of the trace element in natural systems. Asequential extraction scheme (SES) was developed for identification of Se oxidation states that first employed 0.1 M (pH 7.0) K2HPO4-KH2PO4 (P-buffer) to release soluble selenate (Se+VI) and selenide (Se-II) and ligand-exchangeable selenite (Se+IV). The second step involved oxidation of organic materials with 0.1 M K2S2O8 (90 °C) to release Se-II and Se+IV associated or occluded …

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Comparative Development Of The Turkey And Chicken Embryo From Cleavage Through Hypoblast Formation, M. R. Bakst, S. K. Gupta, V. Akuffo Jan 1997

Comparative Development Of The Turkey And Chicken Embryo From Cleavage Through Hypoblast Formation, M. R. Bakst, S. K. Gupta, V. Akuffo

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

The development of the turkey and chicken embryo from the first cleavage division through hypoblast formation is described. The early development of the chicken embryo has been categorized into 14 stages. A similar staging sequence for the turkey was not proposed until 1993, when we described the early development of the turkey embryo, which was divided into 11 stages. Comparatively, differences in the temporal and spatial development of the turkey and chicken blastoderm were evident. Of significance is the observation that at oviposition the turkey is in Stage VII and characterized by the first signs of area pellucida formation. In …

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Evaluation Of 41 Elite And Exotic Inbred Sorghum Genotypes For High Quality Callus Production, Heidi F. Kaeppler, Jeffrey F. Pedersen Jan 1997

Evaluation Of 41 Elite And Exotic Inbred Sorghum Genotypes For High Quality Callus Production, Heidi F. Kaeppler, Jeffrey F. Pedersen

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Interest is high in the genetic study and improvement of sorghum(Sorghum bicolor L. Moench), a crop of worldwide agronomic importance. The ability to initiate and maintain high quality (pigmentless, mucilage-free, fast growing, type II) callus cultures from a variety of sorghum genotypes is important for certain tissue culture-based genetic studies. The objective of this study was to identify high-quality callus-producing genotypes from a group of 41 diverse inbred sorghum lines. Callus cultures of 20 elite inbred sorghum genotypes and 21 inbred genotypes of exotic background were initiated from immature inflorescences. The cultures were subjected to several cycles of subculturing …

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Expression Of Follistatin And Inhibin/Activin Subunit Genes In Porcine Follicles, M.D. Li, L.V. Depaolo, J.J. Ford Jan 1997

Expression Of Follistatin And Inhibin/Activin Subunit Genes In Porcine Follicles, M.D. Li, L.V. Depaolo, J.J. Ford

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Expression of the follistatin (FS) and inhibin/activin (I/A) α, βA, and βB subunit genes in porcine ovarian follicles was evaluated by reverse transcriptase polymerase chain reaction and/or RNase protection procedures to establish changes during the final stages of follicular development. For the I/A α and βA subunits, expression increased (p < 0.05) as follicles progressed to the mid-stage of the follicular phase. The βB, subunit was expressed in lower concentrations, and all three I/A subunits showed a marked reduction (p < 0.01) in expression by the late stage of follicular development. In contrast to this pattern, FS gene expression decreased (p < 0.05) as follicles developed from the early (low estradiol) to the mid stage (high estradiol) and continued to decline in advanced follicles (after estrus). The predominant mRNA encoded for FS-315, and the ratio of mRNA for FS-315 to mRNA for FS-288 did not differ significantly during the three stages. Within an animal, concentration of FS mRNAs was related more to stage of the follicular phase than to follicular size. Follicular fluid concentration of FS changed in a manner similar to that observed for expression of its gene. We conclude that expression of the FS gene and translation of its mRNA decrease as follicles approach ovulatory status.

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Effects On White Leghorn Hens Of Constant Exposure To Ultraviolet Light From Insect Traps, Jerome Hogsette, Henry Wilson, Susan Semple-Rowland Jan 1997

Effects On White Leghorn Hens Of Constant Exposure To Ultraviolet Light From Insect Traps, Jerome Hogsette, Henry Wilson, Susan Semple-Rowland

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Constant exposure of Hy-Line® W-36 White Leghorn hens to ultraviolet light from insect traps resulted in no significant differences in egg production, fertility, hatchability of fertile eggs, or total hatchability. Also, there were no apparent effects on the eyes of the birds. Results were the same when either blacklight or blacklight blue tubes were used. The need for additional testing of light traps for nuisance fly control in commercial caged layer houses is discussed.

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Genetic Variation In North American Leafy Spurge (Euphorbia Esula) Determined By Dna Markers, Martha L. Rowe, Donald J. Lee, Scott Nissen, Brunella M. Bowditch, Robert A. Masters Jan 1997

Genetic Variation In North American Leafy Spurge (Euphorbia Esula) Determined By Dna Markers, Martha L. Rowe, Donald J. Lee, Scott Nissen, Brunella M. Bowditch, Robert A. Masters

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Levels of inter- and intrapopulation genetic variation were determined in five North American populations of leafy spurge using chloroplast DNA (cpDNA) RFLPs and RAPD markers. Thirteen plastome types were identified among 123 individuals collected from five geographically separated populations. Number of pastimes within a population ranged from one to seven, with four of the populations having a predominate type plus one or more rarer types. Some plastome types were shared by populations, but plastome distribution among populations was nonrandom. RAPD markers indicated greatest relatedness among individuals within a population. Relatedness among populations as established through RAPDs was greater for geographically …

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Yield Of Wheat Across A Subambient Carbon Dioxide Gradient, Herman S. Mayeux, Hyrum B. Johnson, H. Wayne Polley, Stephen R. Malone Jan 1997

Yield Of Wheat Across A Subambient Carbon Dioxide Gradient, Herman S. Mayeux, Hyrum B. Johnson, H. Wayne Polley, Stephen R. Malone

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Yields and yield components of two cultivars of day-neutral spring wheat (Triticum aestivum L.) were assessed along a gradient of daytime carbon dioxide (CO2) concentrations from about 200 to near 350 µmol CO2 (mol air)–1 in a 38 m-long controlled environment chamber. The range in CO2 concentration studied approximates that of Earth’s atmosphere since the last ice age. This 75% rise in CO2 concentration increased grain yields more than 200% under well-watered conditions and by 80–150% when wheat was grown without additions of water during the last half of the 100-day growing season. …

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In Situ Infrared Speciation Of Adsorbed Carbonate On Aluminum And Iron Oxides, Chunming Su, Donald L. Suarez Jan 1997

In Situ Infrared Speciation Of Adsorbed Carbonate On Aluminum And Iron Oxides, Chunming Su, Donald L. Suarez

United States Department of Agriculture-Agricultural Research Service / University of Nebraska-Lincoln: Faculty Publications

Surface adsorption mechanisms of dissolved inorganic carbon species on soil minerals are not well understood. Traditional infrared (IR) study of adsorbed species of inorganic carbon using air-dried samples may not reveal true species in the solid/water interface in suspension. The purpose of this study was to obtain information on interracial carbonate speciation between solid and aqueous phases. The interaction of bicarbonate and carbonate ions with X-ray amorphous (am) A1 and Fe oxides, gibbsite (y-Al(OH)3 ) and goethite ( α-FeOOH) was examined by electrophoresis and in situ attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. The presence of …

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