Showing papers by "Swedish University of Agricultural Sciences published in 1988"

Stability Analysis in Plant Breeding

Abstract: Article de synthese sur les methodes d'analyse de la stabilite de caracteres genetiques, notamment le rendement en amelioration des plantes

Rodent dynamics as community processes.

Abstract: Small rodent fluctuations are mentioned in many textbooks as examples of regular population cycles with constant interval and amplitude. However, recent evidence and analyses have indicated much more complex patterns, with geographic trends in frequency and amplitude of fluctuations and covariation with many interacting community components. These new findings indicate that extrinsic factors are much more important for the generation of regular rodent cycles than was earlier believed, and that regular cycles represent only a minority of the dynamic patterns found in rodents.

Vehicle and wheel factors influencing soil compaction and crop response in different traffic regimes

Abstract: A review is made of effects of machinery traffic on soils and crops, including stress distribution under running gear, soil response to applied stresses, influence of compaction on soil properties and processes, persistence of compaction, and crop response to compaction. The influence of machinery traffic on the crops is divided into several categories: direct damage to growing plants; effects of the state of compactness of the plough layer; residual effects in this layer after re-loosening; effects of subsoil compaction. Traffic intensity and wheel track distribution in different cropping systems are illustrated, and several possibilities for reducing heavy traffic or its negative effects, or to alleviate compaction, are discussed. The present situation in different parts of the world with regard to soil compaction is evaluated, and examples of economic analyses are presented.

The evolution of partial migration in Birds.

Abstract: Partial migration, i.e.when one fraction of the population is migratory and the other sedentary, appears to be a widespread phenomenon among many animal taxa, ranging from insects to higher vertebrates. Partial migration in birds was first documented for several Holarctic populations many decades ago. The evolution and maintenance of this particular migratory system have only recently been more thoroughly examined, but our knowledge and understanding of the problem is still incomplete. Currently, one of the main concerns is the fitness balancing of the two behavioural alternatives, i.e. whether migrants and residents within a population are equally fit or if one of the categories is inferior and making 'the best of a bad situation'. Closely tied to this question is the proximate regulation of the migratory and sedentary habits. It has been suggested that a social dominance system might be powerful enough to keep this migration system going; alternatively, a pooulation might be divided into two genetically distinct morphs with different preprogrammed Migratory behaviours.

Microbial biomass as a fraction of potentially mineralizable nitrogen in soils from long-term field experiments

Abstract: Aerobic long-term incubations (40-wk) were employed to measure the potentially mineralizable nitrogen (N 0 ) in five 30-yr old cropping systems. The cropping systems consisted of: (1) bare fallow; (2) cropping with no additions; (3) cropping with 80 kg N ha −1 y −1 as Ca(NO 3 ) 2 ; (4) cropping with 80 kg N ha −1 yr −1 as Ca(NO 3 ) 2 plus 1800kg C ha −1 yr −1 as straw; and (5) cropping with 80 kg N ha −1 yr −1 plus 1800 kg C ha −1 yr −1 as farmyard manure. The amounts of N mineralized during the 40-wk incubations were between 93 and 168 μg g −1 (302–543 kg N ha −1 down to 25cm depth) with the lowest value for the fallow and the highest for the farmyard manure treatment. Microbial biomass-C and -N were measured on four occasions during the incubations. The biomass-C showed a rapid decrease to week 4 (to 36% of the initial mass), a slower decrease to week 9 (to 23% of initial mass) and a very slow decline to the final determination at the end of the incubation (to 8% of initial mass). The biomass-N displayed a similar pattern. Two related models were employed to describe the kinetics of N-mineralization during incubation: (1) a two-component first-order; and (2) a simplified special case of the two-component model. In all cases except the straw-amended soil, the simplified two-component model offered the best description of the curves of accumulated mineral-N. The available fraction, N a , of soil organic-N had mineralization rate constants similar to those for mineralization of microbial biomass.

Nutrient uptake and allocation at steady‐state nutrition

Abstract: Ingestad, T. and Agren, G. I. 1988. Nutrient uptake and allocation at steady-state nutrition. - Physiol. Plant. 72: 450–459. Net nutrient uptake and translocation rates are discussed for conditions of steady-state nutrition and growth. Under these conditions, the relative uptake rate is equal to the relative growth rate, for whole plants as well as for plant parts, since the root/shoot ratio and internal concentrations remain stable. The nutrient productivity and the minimum internal concentration are parameters characteristic for the plant and the nutrient. A conceptual, mathematical model, based on these two fundamental parameters is used for calculation and prediction of the net nutrient uptake rate, which is required to maintain steady-state nutrition at a specified internal nutrient concentration or relative growth rate. When uptake rate is expressed on the basis of the root growth rate, there is, up to optimum, a strong linear relationship between uptake rate and the internal concentration of the limiting nutrient. More complicated and less consistent relationships are obtained when uptake rate is related to root biomass. The limiting factor for suboptimum uptake is the amount of nutrients becoming available at the root surface. When replenishment is efficient, e.g. with vigorous stirring, the concentration requirement at the root surface appears to be extremely low, even at optimum. In the suboptimum range of nutrition, the effect of nutrient status on root growth rate is a critical factor with a strong feed-back on nutrition, growth and allocation. At supraoptimum conditions, the uptake mechanism is interpreted as a protection against too high uptake rates and internal concentrations at high external concentration. In birch (Betula pendula Roth.), the allocation of nitrogen to the shoots is high compared to that of potassium and also to that of phosphorus at low nitrogen or phosphorus status. With decreasing stress, phosphorus allocation becomes more and more similar to nitrogen allocation. The formulation of a mathematical model for calculation of allocation of biomass and nutrients requires more exact information on the quantitative dependence of the growth-regulating processes on nutrition.

Reversibility of acidification shown by whole-catchment experiments

Abstract: Manipulation experiments are being conducted in Norway to examine the effects of drastic changes in precipitation chemistry on soil and surface-water acidification. At a clean area in western Norway, two pristine catchments are being acidified by addition of H2SO4 and H2SO4+HNO3, respectively. At an acidified catchment in southernmost Norway, ambient acid precipitation is excluded by means of a roof and clean precipitation added beneath.

Production of gibberellins and indole-3-acetic acid by Rhizobium phaseoli in relation to nodulation of Phaseolus vulgaris roots.

Abstract: Similar ranges of gibberellins (GAs) were detected by high-performance liquid chromatography (HPLC)-immunoassay procedures in ten cultures of wild-type and mutant strains of Rhizobium phaseoli. The major GAs excreted into the culture medium were GA1 and GA4. These identifications were confirmed by combined gas chromatographymass spectrometry. The HPLC-immunoassays also detected smaller amounts of GA9- as well as GA20-like compounds, the latter being present in some but not all cultures. In addition to GAs, all strains excreted indole-3-acetic acid (IAA) but there was no obvious relationship between the amounts of GA and IAA that accumulated. The Rhizobium strains studied included nod − and fix − mutants, making it unlikely that the IAA- and GA-biosynthesis genes are closely linked to the genes for nodulation and nitrogen fixation. The HPLC-immunoassay analyses showed also that nodules and non-nodulated roots of Phaseolus vulgaris L. contained similar spectra of GAs to R. phaseoli culture media. The GA pools in roots and nodules were of similar size, indicating that Rhizobium does not make a major contribution to the GA content of the infected tissue.

A method of selective inhibition to distinguish between nitrification and denitrification as sources of nitrous oxide in soil

Abstract: Nitrapyrin and C2H2 were evaluated as nitrification inhibitors in soil to determine the relative contributions of denitrification and nitrification to total N2O production. In laboratory experiments nitrapyrin, or its solvent xylene, stimulated denitrification directly or indirectly and was therefore considered unsuitable. Low partial pressures of C2H2 (2.5–5.0 Pa) inhibited nitrification and had only a small effect on denitrification, which made it possible to estimate the contribution of denitrification. The contribution of nitrification was estimated by subtracting the denitrification value from total N2O production (samples without C2H2). The critical C2H2 concentrations needed to achieve inhibition of nitrification, without affecting the N2O reductase in denitrifiers, must be individually determined for each set of experimental conditions.

Movements of carabid beetles (Coleoptera: Carabidae) inhabiting cereal fields: a field tracing study

Abstract: The individual movements of four carabid species were investigated by tracing beetles in the field using a portable radar system (harmonic radar). The field-inhabiting a Pterostichus melanarius Illiger, P. niger Schaller and Harpalus rufipes De Geer were traced in cereal fields. The movements of P. melanarius Mnd P. niger were also tracked in a wood and then compared with the movements of the forest-species Carabus nemoralis Muller. P. melanarius and P. niger displayed directed movements in cereal fields, although P. niger moved faster than P. melanarius. The movement pattern of H. rufipes in the field, and C. nemoralis and P. malanarius in the wood can be described as a c correlated random walk. In cereal fields, P. melanarius burrowed actively into the soil, and P. niger searched out crevices. In contrast, none of these two carabids burrowed in the forest soil, whereas C. nemoralis did. No statistically significant difference was observed between the movements of hungry and satiated beetles, although starved beetles tended to disperse shorter distances per move and turned back more often (especially P. niger). The significance of the various movement patterns exhibited by the species studied for their reproduction and survival on arable land is discussed.

Aqueous, High-Temperature Transformation of Carbohydrates Relative to Utilization of Biomass

Abstract: Publisher Summary This chapter discusses the aqueous, high-temperature transformation of carbohydrates. Over the past two decades, considerable interest has been directed toward the conversion of cellulosic biomass (materials such as wood wastes, bagasse, and straw) into useful products, notably fuels. Several procedures, including fermentation, gasification, liquefaction, and pyrolysis, have been commercially applied to carbohydrates with various degrees of success. To use the polysaccharides present in lignocellulosic materials as a substrate in fermentation processes, pretreatments are necessary, such as with steam (under slightly acid conditions) or alkali, followed by acid or enzymic hydrolysis. It is difficult to avoid some unwanted carbohydrate transformations in these pretreatments. Gasification is a rather direct and specific process. Liquefaction (hydrothermolysis) and pyrolysis are not so specific, as the mixtures obtained by these processes indicate that a complex series of mechanisms is involved. This chapter focuses on the transformation of monomeric saccharides the transformation of polysaccharides such as starch and cellulose. It also elaborates the concepts related to carbohydrate transformation in the presence of amino compounds.

Relationships between soil moisture content and nitrous oxide production during nitrification and denitrification

Abstract: The effect of soil water content [60%–100% water-holding capacity (WHC)] on N2O production during autotrophic nitrification and denitrification in a loam soil was studied in a laboratory experiment by selectively inhibiting nitrification with a low C2H2 concentration (2.1 Pa). Nitrifiers usually produced more N2O than denitrifiers. During an initial experimental period of 0–6 days the nitrifiers produced more N2O than the denitrifiers by a factor ranging from 1.4 to 16.5, depending on the water content and length of incubation. The highest N2O production rate by nitrifiers was observed at 90% WHC, when the soil had become partly anaerobic, as indicated by the high denitrification rate. At 100% WHC there were large gaseous losses from denitrification, while nitrification losses were smaller except for the first period of measurement, when there was still some O2 remaining in the soil. The use of 10 kPa C2H2 to inhibit reduction of N2O to N2 stimulated the denitrification process during prolonged incubation over several days; thus the method is unsuitable for long-term studies.

Characterization of the MHC class II region in cattle. The number of DQ genes varies between haplotypes.

Abstract: The organization of the major histocompatibility complex (MHC) class II region in cattle was investigated by Southern blot analysis using human probes corresponding to DO, DP, DQ, and DR genes. Exon-specific probes were also employed to facilitate the assessment of the number of different bovine class II genes. The results indicated the presence of single DO βand DR αgenes, at least three DR βgenes, while the number of DQ genes was found to vary between MHC haplotypes. Four DQ haplotypes, DQ α 1 β 1 to DQ α 2 β 4, possessed a single DQ α and a single DQ βgene whereas both these genes were duplicated in eight other haplotypes, DQ α 3 β 5 to DQ α 9 β 12. No firm evidence for the presence of bovine DP genes was obtained. The same human probes were also used to investigate the genetic polymorphism of bovine class II genes. DQα DQ β , DRα DR β , and DO β restriction fragment length polymorphisms (RFLPs) were resolved and in particular the DQ restriction fragment patterns were highly polymorphic. Comparison of the present result with the current knowledge of the class II region in other mammalian species suggested that the DO, DP, DQ, DR, and DZ subdivision of the class II region was established already in the ancestor of mammals. The DP genes appear to be the least conserved class II genes among mammalian species and may have been lost in cattle. The degree of polymorphism of different class II genes, as revealed by RFLP analyses, shows striking similarities between species.

Nutrition and growth of birch seedlings at varied relative phosphorus addition rates

Abstract: Birch (Betula pendula Roth.) was investigated under steady state nutrition and growth at different relative addition rates of phosphorus (Rp). Phosphorus deficiency symptoms appeared on the leaves when the internal phosphorus concentration decreased, but disappeared again under steady state nutrition, independent of the stress level. The increased root/shoot ratio and the exploratory type of root systems developed during the adjustment stage remained under steady state conditions. At nonoptimum and close to optimum relative addition rates, independent of the rate, the phosphorus concentration of the culture solution did not exceed 2 μmol dm−3 and was generally < 1 μmol dm−3 immediately after phosphorus additions. The phosphorus concentration just before additions was generally < 0.5 μmol dm−3. The nutrition/growth relationships were similar to those for nitrogen, with relative growth rate (Rg) closely related to the Rp applied and with a strong linear relationship between internal phosphorus concentration and Rg. Regression was much steeper than that for nitrogen. The slope of the optimum nutrition was attained at a lower phosphorus weight proportion to nitrogen (8–10 P: 100 N) than previously estimated (= 13 P: 100 N), but a higher relative phosphorus requirement was observed under stress conditions. Birch seedlings had a strong tendency to consume phosphorus in excess of immediate requirements with a small effect on growth above optimum. This resulted in rapidly decreasing phosphorus productivity (Pp, growth rate per unit of phosphorus) with increasing internal phosphorus concentrations above optimum.

Linkage relationships in the bovine MHC region. High recombination frequency between class II subregions.

Abstract: Class II genes of the bovine major histocompatibility complex (MHC) have been investigated by Southern blot analysis using human DNA probes. Previous studies revealed the presence of bovine DO β , DQ α , DQ β , DR α and DR β genes, and restriction fragment length polymorphisms for each of these genes were documented. In the present study, the presence of three additional class II genes, designated DZ α , DY α , and DY β , are reported. DZ α was assumed to correspond to the human DZ α gene while the other two were designated DY because their relationship to human class II genes could not be firmly established. The linkage relationships among bovine class II genes and two additional loci, TCP1B and C4, were investigated by family segregation analysis and analysis of linkage disequilibrium. The results clearly indicated that all these loci belong to the same linkage group. This linkage group is divided into two subregions separated by a fairly high recombination frequency. One region includes the C4, DQ α , DQ β , DR α and DR β loci and the other one is composed of the DO β DY α , DY β , and TCPIB loci. No recombinant was observed within any of these subregions and there was a strong or fairly strong linkage disequilibrium between loci within groups. In contrast, as many as five recombinants among three different families were detected in the interval between these subregions giving a recombination frequency estimate of 0.17 ± 0.07. The fairly high recombination frequency observed between class 11 genes in cattle is strikingly different from the corresponding recombination estimates in man and mouse. The finding implies either a much larger molecular distance between some of the bovine class II genes or alternatively the presence of a recombinational “hot spot” in the bovine class II region.

Analysis of Indole-3-Acetic Acid and Related Indoles in Culture Medium from Azospirillum lipoferum and Azospirillum brasilense.

Abstract: Analysis of neutral and acidic ethyl acetate extracts from culture medium of Azospirillum brasilense 703Ebc by high-performance liquid chromatography (HPLC) and combined gas chromatography-mass spectrometry demonstrated the presence of indole-3-acetic acid (IAA), indole-3-ethanol, indole-3-methanol, and indole-3-lactic acid. IAA in media of 20 strains of A. brasilense and Azospirillum lipoferum was analyzed quantitatively by both the colorimetric Salkowski assay and HPLC-based isotopic dilution procedures. There was little correlation between the estimates obtained with the two procedures. For instance, the Salkowski assay suggested that the culture medium from A. brasilense 703Ebc contained 26.1 μg of IAA ml−1, whereas HPLC revealed the presence of only 0.5 μg of IAA ml−1. Equivalent estimates with A. brasilense 204Ed were 10.5 and 0.01 μg of IAA ml−1, respectively. The data demonstrate that the Salkowski assay is not a reliable method for measuring the IAA content of Azospirillum culture medium and that estimates in excess of 10 μg of IAA ml−1 should be viewed with particular caution. Metabolism of [2′-14C]IAA by A. brasilense 703Ebc yielded radiolabeled indole-3-methanol, whereas roots of maize (Zea mays L.) seedlings gave rise to [14C]oxindole-3-acetic acid and an array of polar metabolites. Metabolism of [2′-14C]IAA by maize roots inoculated with A. brasilense 703Ebc produced a metabolic profile characteristic of maize rather than Azospirillum species.

Binding of human extracellular superoxide dismutase C to sulphated glycosaminoglycans

Abstract: The secretory enzyme extracellular superoxide dismutase (EC-SOD) occurs in at least three forms, which differ with regard to heparin affinity: A lacks affinity, B has intermediate affinity, and C has relatively strong affinity. The affinity of EC-SOD C for various sulphated glycosaminoglycans (GAGs) was assessed (a) by determining the concentration of NaCl required to release the enzyme from GAG-substituted Sepharose 4B and (b) by determining the relative potencies of the GAGs to release EC-SOD C from heparan sulphate-Sepharose 4B. Both methods indicated the same order of affinity. Heparin bound EC-SOD C about 10 times as avidly as the studied heparan sulphate preparation, which in turn was 10 and 150 times as efficient as dermatan sulphate and chondroitin sulphate respectively. Chondroitin sulphate showed weak interaction with EC-SOD C at physiological ionic strength. Heparin subfractions with high or low affinity for antithrombin III were equally efficient. The binding of EC-SOD C to heparin-Sepharose was essentially independent of pH in the range 6.5-9; below pH 6.5 the affinity increased, and beyond pH 9.5 there was a precipitous fall in affinity. The inhibitory effect of NaCl on the binding of EC-SOD C to GAGs indicates that the interaction is of electrostatic nature. EC-SOD C carries a negative net charge at neutral pH, and it is suggested that the binding occurs between the negative charges of the GAG sulphate groups and a structure in the C-terminal end of the enzyme that has a cluster of positive charges. These results are compatible with the notion that heparan sulphate proteoglycans on cell surfaces or in the intercellular matrix may serve to bind EC-SOD C in tissues.

High performance liquid chromatography determination of ergosterolas a measure of ectomycorrhiza infection in Scots pine

Abstract: A technique for determining the ergosterol content in mycorrhizal pine roots using HPLC was developed. Pure cultures of different my corrhizal fungi contained very similar and constant amounts of ergosterol, and calculations of fungal biomass in mycorrhizal roots based on ergosterol readings agreed well with results using other methods. The extraction and sample purification were simple and reliable. Consequently, the technique is considered practical wherever accurate estimates of the intensity of mycorrhizal infection are required.

Cholesterol Oxides in Swedish Foods and Food Ingredients: Milk Powder Products

Abstract: Cream-, whole milk-and skim milk powders had 1.6, 2.0, and 18.9 mg cholesterol/g fat, respectively. About 90% of the cholesterol was unesterified. Analyses of fresh spray-dried whole-and skim milk powders from “low and medium heat” conditions and fresh roller-dried whole milk powder from “low heat” conditions contained less than 0.1 ppm cholesterol oxides in lipids. However, spray-dried whole-and skim milk powders from “high heat” conditions had substantial levels of some important cholesterol oxides. Skim-milk powders, stored in big sacks for 11–37 months and small consumer packages for 2–23 months, contained variable amounts of 5, 6α-epoxy-5β-cholestan-3β-ol (0.3–4.0 ppm), 5,6β-epoxy-5α-cholestan-3β-ol(0.7–10.40ppm), cholest-5-ene-3β,7α-diol(0.5–16.2 ppm), cholest-5-ene-3β,7β-diol(1.3–20.8 ppm), cholest-5-ene-3β,20α-diol(0.6–2.7 ppm), cholest-5-ene-3,25-diol(0.3–0.8 ppm), 5α-cholestane-3β,5,6β-triol(1.3–2.5 ppm) and 3-hydroxy-cholest-5-en-7one(1.8-24.9 ppm).

The vertical distribution of fine roots of five tree species and maize in Morogoro, Tanzania

Abstract: In order to assess the possibility of root competition in agroforestry, the vertical distribution of fine roots (< 2 mm in diameter) of five tree species in pure two-year-old stands was compared to that of mature maize.Cassia siamea, Eucalyptus tereticornis, Leucaena leucocephala andProsopis chilensis had a rooting pattern similar to that of maize, i.e. a slow decline in fine root mass from 0–100 cm soil depth.Eucalyptus camaldulensis had its roots evenly distributed down to 100 cm. On an average, the fine root biomass of the tree species was roughly twice as that of the maize. We conclude that the studied tree species are likely to compete with maize and other crops with a similar rooting pattern for nutrients and water.

Effects of transport stress on concentrations of cortisol, corticosteroid-binding globulin and glucocorticoid receptors in pigs with different halothane genotypes.

Abstract: Effects of stress on concentrations of cortisol and corticosteroid-binding globulin (CBG) in blood plasma and on glucocorticoid receptor concentrations in muscle cytosol were studied in pigs representing three Halothane (Hal) genotypes (NN, Nn, nn). At 12 wk of age, animals were divided into four groups: pigs subjected to transport (5 h in a truck), pigs treated with amperozide prior to transport, pigs not transported but treated with amperozide and pigs neither transported nor given amperozide. Animals were slaughtered the week they reached 100 kg live weight (3 mo later). The Hal gene showed no major influence on the variables studied except for cortisol concentrations (P = .06) measured directly after transport at 12 wk of age (NN = 66.8 nM, Nn = 61.4 nM, nn = 69.4 nM). However, the response in each Hal genotype differed, depending on whether or not the pigs had been exposed to transport. Two weeks after transport, NN pigs developed higher cortisol concentrations than untransported animals, whereas the response was reversed in nn animals; Nn pigs showed no difference in this regard. At slaughter, the effect of transport (12 wk of age) on cortisol and CBG was still apparent. In NN pigs cortisol and CBG concentrations were elevated (P less than or equal to .05, P = .08, respectively), whereas concentrations tended to be lower in nn pigs (P = .17, P = .07, respectively) when compared with untransported pigs. Transported pigs had lower receptor concentrations at slaughter (P less than or equal to .01) than untransported pigs. However, pigs given amperozide in connection with transport had a receptor concentration comparable to that in untransported pigs. Our study shows conclusively that transport stress had long-term effects on cortisol, CBG and glucocorticoid receptor concentrations. In addition, amperozide had long-term effects on cortisol and receptor concentrations.