Showing papers by "University of Reading published in 1971"

Relationships between weedy and cultivated forms in some species of chili peppers (genus capsicum).

Abstract: A question which often arises in studies on the origin and evolution of cultivated plants is whether a weedy race of a crop plant is ancestral to the crop or whether it is necessary to look further for a wild progenitor. Work on a number of different crop-weed complexes has shown that three types of relationship are possible. The weed may have given rise to the crop, as appears to have happened in rye, oats and hemp (Vavilov, 1926). In other cases, such as radish (Panetsos and Baker, 1967) and rye (Suneson et al., 1969) in California, the weedy races may be derived from the crop, usually by hybridisation with related wild species. Thirdly, both crop and weed may be derived from a common ancestral wild population by disruptive selection, as has been suggested by Harlan (1965). The genus Capsicum contains about 20 species, all of which originated in the New World. Some of these are wild species which occur as natural components of undisturbed vegetation, although their fruits may be collected and used by man. Four species (C. annuum, C. baccatum, C. clhinense and C. pubescens) are widely cultivated in Latin America. Each is characteristic of a different area, though their ranges now overlap. C. annuum is widespread in Mexico and Central America but cultivated forms of this species seem to have reached South America rather late, possibly after the Spanish Conquest (Smith and Heiser, 1957). C. baccatum is the common cultivated chili pepper of Peru and Bolivia. It extends northwards to Ecuador and southern Colombia and eastwards to south-eastern Brazil. In the West Indies, northern South America and the Amazon basin the pepper most commonly cultivated is C. chinense. This species is also common in Peru and Bolivia and thus overlaps the range of C. baccatum. C. pubescens is more tolerant of low temperatures than the other cultivated peppers and is found at higher altitudes in the Andes. It extends along the mountains from Bolivia to Colombia and has now reached Mexico. It is sympatric with C. annuumn, C. baccatum and C. chinense in the lower parts of its altitudinal range, but it is morphologically very distinct and is reproductively isolated from the other three species. In both C. annuum and C. baccatum there are, besides the large-fruited cultivated types which have lost their natural mechanisms for seed dispersal, uncultivated forms with small erect deciduous fruits which can be dispersed by birds and other agents. Few observations have been made on the ecology of these uncultivated forms, but they seem usually to occur as weeds of cultivated ground or in other disturbed habitats such as roadsides and margins of rivers. They are recognised taxonomically as distinct varieties, C. annuum var. minimum and C. baccatum var. baccatum, while the cultivated plants are assigned to C. annuum var. annuum and C. baccatum var. pendulum. C. annuum var. minimum has erroneously been called C. baccatum in some of the earlier literature, but Hunziker (1950) has shown this to be a misapplication of the name C. baccatum. The situation with regard to C. chinense is a little more complicated. There are no unequivocal reports of wild or weedy plants belonging to this species. However, there is a closely related species, C. frutescens, most collections of which have small deciduous fruits and occur in weedy situations.

Bacteria Associated with the Intestinal Wall of the Fowl (Gallus domesticus)

Abstract: Using histological and cultural techniques bacteria associated with the intestinal wall of the chick have been demonstrated. The main sites of adhesion were the crop, ileum and caecum. The pattern of attachment was characteristic for each site.

Atmospheric Fluorine Compounds as Indicators of Air Movements

Abstract: GASEOUS fluorine compounds are supposed not to occur naturally in the atmosphere. Volatile fluorine compounds would not be expected to result from chemical equilibria between fluorine compounds on the surface of the Earth, and it is improbable that biological systems contribute significant quantities of organic fluorine compounds.

Mechanisms of azo reduction by Streptococcus faecalis. II. The role of soluble flavins.

Abstract: 1. Using a previously developed continuous assay system, the mechanism of stimulation of Red 2G azo reduction in Streptococcus faecalis by additions of soluble flavins has been investigated.2. Reduced flavins acting as two-electron donors can rapidly reduce Red 2G non-enzymically and the reduced flavins can act as an electron shuttle from NAD(P)H-dependent flavoproteins to the acceptor azo compound.3. Results of inhibition studies were consistent with the direct participation of soluble flavins and the non-involvement of cytochromes in azo reduction.4. Enzyme fractions possessing azo-reductase activity also showed cytochrome c reductase and diaphorase activity, and respired oxygen. Azo reduction under anaerobic conditions may represent a fortuitous, non-enzymic reduction by enzymically-generated reduced flavins; inhibition by oxygen being due to regeneration of the oxidized form.

Entropy and Other Measures of Concentration

Abstract: In recent years, economists have begun to use the entropy, or redundancy, of a size distribution to measure the extent to which business is concentrated in the control of giant firms. This paper compares these new measures derived from information theory with the classical statistical measures of dispersion and with traditional measures of business concentration derived from the cumulative concentration curve. It shows that when the number of firms is large enough to use statistical distribution theory, the classical statistical measures are superior to the entropy or the redundancy. When the number of firms is small, the entropy is superior to the redundancy, but both are inferior to the traditional measures of concentration derived from the cumulative concentration curve. Consequently, there is little point in using the information theory measures to measure business concentration.

The performance of brevicoryne brassicae and myzus persicae in relation to plant age and leaf amino acids

Abstract: With increasing plant age, total soluble nitrogen of Brussels sprout plants decreased after a peak at 6–9 weeks. The plants then became less suitable for Brevicoryne brassicae and Myzus persicae (particularly the latter) as shown by estimates of the mean relative growth rate (RGR) of the aphids in two experiments. This growth statistic was, however, only poorly correlated with total soluble N and this lack of correlation was particularly marked on plants less than 9 weeks old. Multiple regression on the leaf amino acid spectrum indicated that much of the variability in aphid RGR could be assigned to relatively few amino acids. The complex of asparagine and glutamine gave a positive coefficient for both aphids, but otherwise different amino acids were involved in the regression for each aphid. Attention is drawn to the presence in each regression of an amino acid with a negative coefficient; the inverse correlation of M. persicae RGR with amino-butyric acid may be particularly important in the aphid/hostplant relationship. Zusammenfassung GEWICHTSWACHSTUMSRATE VON BREVICORYNE BRASSICAE UND MYZUS PERSICAE IN BEZIEHUNG ZUM PFLANZENALTER UND ZU DEN IN DEN BLATTERN ENTHALTENEN AMINOSAUREN In einem ersten Versuch zeigte sich, das der Gehalt an loslichem Stickstoff in den Blattern mit dem Alter der Pflanzen zwischen 8 und 20 Wochen standig abnahm. Die relative Wachstumsrate (RGR) von Brevicoryne brassicae veranderte sich dabei kaum, jedoch waren die einzelnen Werte der RGR und des loslichen Stickstoffgehalts der entsprechenden Pflanzen gut korreliert. Dagegen reagierte Myzus persicae unmittelbarer auf das Pflanzenalter als auf den Stickstoffgehalt und ihre RGR nahm ab, je alter die Pflanzen wurden. Im zweiten Versuch wurden jungere Pflanzen benutzt. Hier stieg der Gehalt an loslichem Stickstoff bis zu einem Hohepunkt in der neunten Woche an. Unabhangig vom Stickstoffgehalt nahm die RGR bei M. persicae wieder ab, je alter die Pflanzen wurden. In diesem Versuch wurde auch der Aminosauregehalt der Blatter analysiert. Die Variabilitat der RGR beider Blattlausarten war mit 4 Aminosauren korreliert. Sowohl Asparagin wie Glutamin zusammen waren dabei fur beide Blattlausarten wichtig; daneben erschienen Threonin und Phenylalanin in der Korrelationsgleichung fur B. brassicae, Methionin und Aminobuttersaure in der fur M. persicae. Fur M. persicae konnten so 42% der gesamten Variabilitat der RGR durch die Korrelationsgleichung erklart werden; fur B. brassicae nur 21%. Von besonderem Interesse ist 1) das sich 42% der M. persicae-Variabilitat mit der Verfugbarkeit von nur 4 Aminosauren erklaren lassen, 2) das die Korrelation zwischen Blattlaus-Wachstumsrate und Asparagin + Glutamin vielleicht dem oft nachgewiesenen Zusammenhang zwischen Pflanzenempfindlichkeit und loslichem Stickstoff entspricht, 3) das die Wachstumsraten der beiden Blattlausarten negativ mit je einer Aminosaure korreliert sind: mit Phenylalanin bei B. brassicae und, sehr wichtig, mit Aminobuttersaure bei M. persicae und 4) das die Resultate bezuglich M. persicae ziemlich gut mit Resultaten bei kunstlichen Ernahrungsversuchen anderer Autoren ubereinstimmen.

On the ecology of a dense bed of the brittle-star Ophiothrix fragilis

Abstract: INTRODUCTIONThe occurrence of dense beds of the brittle-star Ophiothrix fragilis (Abildgaard) in certain localized areas around the British Isles has been reported by several authors (Allen, 1899; Vevers, 1952; Cabioch, 1961; Holme, 1961; Brun, 1969), with population densities varying from 340/m2 (Vevers, 1952) to 2196/m2 (Brun, 1969). These populations seem to be permanent features of the sea bed since the aggregation sampled by Allen was in the same position as that photographed by Vevers fifty years later.

The Microbial Flora of the Rumen of Cows Fed Hay and High Cereal Rations and its Relationship to the Rumen Fermentation

Abstract: Summary. The rumen microbial population associated with feeding cows 3 rations, hay alone, 20% hay/80% flaked maize and 20% hay/80% rolled barley has been examined. The differences between the hay and the cereal rations were considerable but between the cereal rations only slight. Both cereal rations provoked & large drop in the proportion of butyrivibrios, and a rise in the proportion of selenomonads, peptostreptococci, lactobacilli and bifidobacteria. The importance of these and other changes occurring in the microbial flora are discussed in relation to their possible effect on the products of the rumen fermentation.

Plant population, shading and thinning studies in wheat

Abstract: Three wheat experiments are described in which a range of plant populations were shaded during different periods of development; in two of the experiments plant thinning was also carried out at a number of growth stages. Shading during the period of ear development caused an appreciable decrease in grain yield by decreasing the number of grains per ear. Shading during the grain filling period also reduced grain yield, this being brought about by decreased grain size. Thus in contrast to the barley experiments reported earlier (Willey & Holhday, 1971), these particular results gave no indication of a potential surplus of carbohydrate for grain filling and an associated limited ear capacity. However, when plant thinning was carried out at anthesis to make more carbohydrate available for grain filling in the remaining ears, grain yield per ear did not increase. It is argued, therefore, that grain yield probably was determined at least partly by a limited ear capacity. Plant thinning at earlier stages showed how the development of competition during the ear development period progressively reduced the potential capacity of the ear; the greater competition of higher plant populations accelerated this reduction in ear potential.From an examination of the effects of plant population, it is suggested that the number of grains per ear is the component having greatest influence on the decline in grain yield at above-optimum populations. The possible importance of the number of grains per unit area as an indicator of ear capacity on an area basis, and as a determinant of grain yield per unit area, is emphasized. A close relationship between grain yield per unit area and number of grains per unit area is illustrated for a number of plant-population response curves, and it is suggested that the decrease in grain yield at high populations is probably determined by a decrease in the number of grains per unit area. Evidence is presented to substantiate the idea put forward in the barley paper that this decrease in the number of grains per unit area may be attributable more to a lower production of total dry matter by the high populations during the later stages of ear development, than to an unfavourable partitioning of such dry matter between the ear and the rest of the plant.

Modelling Cities as Dynamic Systems

Abstract: Most attempts at building mathematical models of cities treat such systems as if they are in static equilibrium. But models which simulate the dynamics of change in cities seem to be more relevant to urban research and planning. The design and application of such a model are described in this article.

Contribution of young fish to total production of fish in the River Thames near Reading

Abstract: The production of the young stages of four species of cyprinid fish in the River Thames was estimated. From the time when underyearling fish became fully vulnerable to the special fine mesh net used, to the end of their first year, production is 39 g/ma/year compared with 83-3 g/m2/year for fish over 1-year old. The contribution of fecundity to population production varied widely, from 6.1 to 0.4 g/m2/year, but was only a small part of total production. The most productive part of the population was that found between spawning and prior to full vulnerability to the net. Production of this part of the population could be estimated only indirectly and was found to be 58-6 g/m2/year. In the four populations studied production during the first year of life was 66 to 73 % of total cohort production in 1967 and only 39 to 64% in 1968. Total fish production in the Thames was estimated at 197 k cal/m2/year; this high result is a consequence of the very high densities found: up to 96-9 fish/m2 were present in August 1967. Ten km of the Thames would contain about 54 000 000 fish in August, falling to around 8 000 000 in winter. The production: biomass ratios for the four species varied from 1–1 to 1′9 in 1967 and from 0–7 to 2-0 in 1968. Very heavy, possibly density dependent, mortality occurs in the first year of life; the annual instantaneous mortality rates are very high, ranging from 6–4 to 8–7. Mortality is heaviest during the first 2 to 3 months after spawning; the instantaneous mortality rates during this period vary from 4-0 to 7-3.

A quantitative analysis of the literature concerning the restricted feeding of growing pullets

Abstract: Synopsis The sexual maturity of growing pullets can be retarded either by restricting calorie intake or by feeding a diet deficient in one or more essential amino acids, Several methods have been proposed for achieving either of these objectives. In this review the methods have been classified as (a) limiting the birds’ time of access to food, (b) quantitative food restriction, (c) the use of low energy diets and (d) dietary protein restriction. Food restriction by limiting the time of access to food has given inconsistent results and is an unsatisfactory technique. Birds quickly learn to eat normal quantities of food in a very short space of time. Quantitative food restriction has been widely used in experiments and is usually applied from about 6 to about 20 weeks of age. The available evidence enables relationships to be established between the degree of food restriction and subsequent body weight and sexual maturity. The effect of rearing treatment on mortality and rate of lay is also examined. The ad...

Attenuation of Stimulus Sensitivity induced by Scopolamine

Abstract: SEVERAL studies have shown that scopolamine hydrobromide, a peripheral cholinergic blocking agent1, increases responding in situations which require response suppression2,3. Other studies4 have demonstrated similar behavioural effects when cholinergic function was modified by anticholinesterases. This disruption has been attributed to either impairment of sensory input2 or response disinhibition5. These hypotheses were tested by using a form of analysis based on the theory of signal detectability (TSD), which originated in work on electronic communication systems and has been extended to sensory psychology6. It has been particularly useful in psychophysics because it yields independent estimates of a subject's sensitivity to stimuli and his response bias.

The influence of washings of living roots on nitrification

Abstract: The effects of washings of plant roots on the rate of nitrification in soil was investigated. The root washings were obtained by leaching columns of quartz chips in which plants were growing, with their roots bathed in nutrient solution. The root washings and ammonium solution were then added to columns of clay loam soil in which ammonium-ion was being converted to nitrate-ion at the rate of c. 370 mg N/kg soil/day. Rates of nitrate formation and ammonium disappearance were estimated by analysis of leachates from the soil columns. The root washings of all plants investigated (ryegrass, wheat, salad rape, lettuce and onion) reduced the rate of nitrification but the effects of rape and lettuce were temporary. Ryegrass root washings had the most pronounced and persistent effects and reduced the rate of nitrification (up to 84 per cent) in proportion to concentration. The rate of nitrification was not limited by supplies of ammonium-ion or other nutrients and there was no reduction of nitrate in the soil columns. As neither microbial immobilization of inorganic-nitrogen nor denitrification appeared to be taking place in the presence of root washings, it was concluded that root washings can in some way retard nitrification although no mechanism was demonstrated.

Near ultra-violet spectra of the s-trans and a second rotamer of acrolein vapour

Abstract: The rotational contour of the 0-0 band of the 1 A″(nπ*)-1 A′ system of s-trans acrolein has been analysed. Interpretation of the excited state rotational constants shows that the changes in angles CCC and CCO, if assumed to be equal, are between +3° and +4° over a large range of Δr C=C, Δr C=O and Δr C-C and, if Δr C=C Δr C=O are assumed equal, then Δr C-C≈ - Δr C=C over a large range. Weaker bands, to low wavenumber of the 1 A″(nπ*)-1 A′ system of s-trans acrolein, are sorted by their temperature dependence and characteristic contours into two systems: the 4120 A system is the 3 A″(nπ*)-1 A′ system of s-trans acrolein while the 4060 A system is shown to be the 1 A″(nπ*)-1 A′ system of s-cis (or possibly ggauche) acrolein. Evidence for this has been obtained from ground state vibration wavenumbers, rotational band contours and temperature effects. Temperature dependence of the intensity of bands has been used to show that the separation of the s-trans and s-cis zero-point levels in the ground electronic s...

Force Constants and Lattice Frequencies

Abstract: It is shown that the force constants of a solid cannot be deduced from the lattice frequencies alone. The fact that a set of force constants agrees with the frequencies exactly is no guarantee that the force constants are even approximately correct. Detailed eigenvector measurements would resolve the uncertainty. A solid has many more force constants than frequencies. The usual procedure gets round this by retaining only the largest force constants and then using at least as many frequencies as the number of retained force constants to calculate the latter. This procedure is incorrect, because neglecting the small force constants limits the accuracy to which the frequency data can be used to calculate the retained constants. In fact, the number of data that can be extracted from the frequency measurements is always less than the number of force constants one wants to calculate. Therefore, even if all the lattice frequencies were known exactly they could still be satisfied with a very wide range of very different sets of force constants. A large proportion of these sets cannot be rejected on the basis of physical criteria alone. Using the methods of continuous transformation theory, for diamond all the ways are constructed in which the force constant matrix can be changed continuously without altering the agreement with the frequencies. A numerical example is included.

Deformation and pressure in an elastohydrodynamic contact

Abstract: The film shape, pressure and temperature profiles have been measured in a disk machine under conditions of elastohydrodynamic lubrication. They were obtained with a new design of transducer which enables the various measurements to be accurately inter-related. In the case of the film shape and pressure measurements the corresponding theoretical solutions have been calculated and detailed comparison made. It has been shown that the sharp peaks of pressure near the outlet which are predicted in the theory are in practice considerably attenuated but do occur in the correct positions. The associated dip in film thickness is also much reduced. Johnson’s recent postulate that the position of the pressure spike should be a function of a single parameter has been examined and found to hold for this new range of experimental data.

Optical and structural properties of MoSe2

Abstract: Single crystals of α-MoSe2 have been prepared which are superior to those grown using a chemical transport agent. The dielectric constant of α-MoSe2 has been measured over the range 0.5 to 3.5eV and a value for the direct optical band gap deduced from the observed exciton spectrum; this is compared with the measured activation energy of intrinsic electrical conduction. Einkristalle von α-MoSe2 wurden hergestellt, die denen, die mit chemischen Transportmitteln gezuchtet werden, uberlegen sind. Die Dielektrizitatskonstante von α-MoSe2 wurde im Bereich von 0,5 bis 3,5 eV gemessen und ein Wert fur die direkte optische Bandlucke aus dem beobachteten Exzitonenspektrum bestimmt, der mit der gemessenen Aktivierungsenergie der elektrischen Eigenleitung verglichen wird.

Mechanisms of azo reduction by Streptococcus faecalis. I. Optimization of assay conditions.

Abstract: 1. A new method for the assay of azo-reductase activity in Streptococcus faecalis and several other microbial species is reported. The assay is continuous and permits a more rapid and accurate determination of specific activity than previously reported assays.2. Optimal cofactor concentrations, pH and temperature have been determined for Streptococcus faecalis azo-reductase.3. A lag period is observed before reduction proceeds at a constant rate and is probably due to generation of required reduced cofactors. The lag time depends on enzyme activity and cofactor concentrations and this variable may have been overlooked in earlier assay procedures.

Plant population and shading studies in barley

Abstract: Two barley experiments are described in which a range of plant populations were shaded during different periods of development. Shading during the ear development period caused considerable reductions in grain yield, largely by reducing the number of grains per ear. Shading during the grain-filling period caused no reduction in grain yield. It is suggested that under conditions of these experiments there was probably a potential surplus of carbohydrate available for grain filling and that grain yield was largely determined by the storage capacity of the ears. The importance of the number of grains per ear as an indicator of individual ear capacity is emphasized.The effects of plant population on grain yield and its components are also examined. It is concluded that the number of grains per ear is the component having greatest influence on the decrease in grain yield at above-optimum populations and attention is again drawn to the possible importance of ear capacity. It is argued that on an area basis the number of grains per unit area may give a good indication of ear capacity. Examination of this parameter shows a close relationship with grain yield per unit area for both the shading and population treatments. It is particularly evident that a decrease in grain yield at high populations was associated with a comparable decrease in the number of grains per unit area. It is suggested that this decrease in grain number may be due to a lower production of total dry matter during ear development rather than an unfavourable partitioning of this dry matter between the ear and the rest of the plant. This lower production of total dry matter is attributed to the crop growth rates of the higher populations having reached their peak and then having declined before the end of the ear development period. This crop growth rate pattern, through its effect on grain number per unit area, is put forward as the basic reason why, in the final crop, grain yield per unit area decreases at above-optimum populations.

Crystallization of polyethylene at elevated pressures

Abstract: The crystallization from the melt of three sharp polyethylene fractions has been studied at 5 kbar. It has been shown that the thickness of so-called extended-chain lamellae is a function of time, temperature, and molecular weight. There is by no means just the fully extended molecular configuration present. Crystallization is qualitatively similar to that of chain-folded crystals at 1 bar, giving an optimum lamellar thickness which increases with time and decreasing supercooling. Fractional crystallization is widespread and is a major cause of disparate lamellar thickness. Isothermal thickening of lamellae during crystallization has been established directly. Morphological detail suggests further that layers can increase their thickness tenfold over their initial size.

Shallow Water Sedimentation: As Illustrated in the Upper Devonian Baggy Beds

Abstract: Summary The Baggy Beds (440 m thick) form a transgressive sequence of shallow-water marine and delta-like sediments of Upper Famennian age between the continental Pickwell Down Sandstone and the overlying neritic Pilton Beds (which straddle the Devonian-Carboniferous boundary). The Baggy Beds are divided into lower and upper divisions (the lower division containing the bulk of the sandstones) and a number of members. There is a strong diversity of facies, and nine main facies are recognized; they show little evidence of cyclicity but their stratigraphical relationships are important for their interpretation. Penecontemporaneous erosion, principally attributed to wave-action, was often intense, and has contributed more than any other factor to the overall aspect of the marine facies. The bulk of the sediment comprises the shales, siltstones, and very fine sandstones of the Diplocraterion yoyo facies group, which display all gradations from non-life (letal) graded siltstones and shales to intensely bioturbated sandstones, in which the trace-fossil D. yoyo is generally conspicuous. The Reynard facies comprises graded sets of fine to very fine sandstones, the upper portions of which commonly show oscillation ripple or are bioturbated. The sets are intercalated singly in the D. yoyo facies, or form cosets (11 per cent of Baggy Beds). These two facies, which yield a small neritic fauna, are considered to represent deposits of the delta-front platform, or a like off-shore environment, with the cosets of Reynard facies for the most part representing a nearer-shore environment. The other facies (with an interpretation of their depositional environment) are as follows: Arenicolites curvatus facies (6 per cent), which include thin, fine to very fine sandstones with A. curvatus and bioturbated sandstones: sub-beach environment. Rough facies (1 per cent), thin sets of shelly, cross-stratified sandstones with Dolabra , and intraformational conglomerate of local derivation: near-shore, shelly, and possibly intertidal channel fills. Gull facies (1 per cent), cross-stratified fine well-sorted sandstones: near-shore submarine dune depositis. Lingula facies (8 per cent), bioturbated and pene-contemporaneously eroded graded siltstones and shales with patches of disarticulated Lingula and thin bellerophontoid limestones: lagoonal or restricted bay environment, possibly brackish. Timber and Cormorant facies (11⋅5 per cent), channel-fill sediments with parallel and cross-stratified fine to very fine sandstones of northerly provenance with much plant debris: distributary fills. (Cormorant subfacies represents deposition mainly under upper flow regime.) Tag facies (5 per cent), multiple channel-fill sediments deposited under lower flow intensity with fine to very fine sandstones and silt-grade sediments, in which small-scale cross-lamination is important: interpretation doubtful, possibly distributary mouth bar deposits, or crevasse fill or the fill of an off-shore barrier inlet. Hoe facies (1⋅5 per cent), shales and siltstones associated with Timber and Tag facies: deposited under conditions of low flow intensity, or in fresh-water lakes. Plant remains and, rarely, Chondrites? parvus . A model is erected (Fig. 27) suggesting that the sediments were deposited in the vicinity of a delta or similar fluvially influenced environment, subject to a moderate tidal range, though largely on the delta-front platform, or relatively inshore on the continental shelf.