Showing papers by "The Hertz Corporation published in 1980"

An evaluation of techniques for measuring vesicular arbuscular mycorrhizal infection in roots

Abstract: Summary Assessment of infection is an essential part of many studies involving VA mycorrhiza. A summary is given of the range of techniques that have been used. We calculated the standard error of four methods of assessment based on observations of stained root samples either randomly arranged in a petri dish or mounted on microscope slides. The methods are based on presence or absence of infection at root/grid intersect points, on a visual estimate of percentage cortex occupied by fungus or on estimates of length, or presence or absence of infection in root pieces mounted on slides. The number of replicate observations required for a given standard error % infection can be read from the curves provided. The advantages of the different methods of assessment are discussed and reasons given why they all probably overestimate the true values.

Estimation of Root-knot Nematode Infestation Levels on Roots Using a Rating Chart

Abstract: A rating chart is given which enables easy and accurate field assessment of damage by root-knot nematodes (Meloidogyne spp.) on many crops, based on the percentage and types of roots galled. It should be of use both to nematologists and untrained field workers.

Daylength change and leaf appearance in winter wheat

Abstract: In the field successive leaves of winter wheat appear at a rate which varies because it depends strongly upon temperature. When plotted against ‘thermal time’, however (temperature accumulated above a fixed base of 0°C), leaf appearance was a strictly linear function of temperature. The mean rate of leaf appearance in thermal time, R′, was faster for a spring sowing than for an autumn sowing. The variation in R′ between sowings was better correlated with the rate at which daylength was changing when the plants emerged than with the mean daylength while leaves were appearing.

Influence of plant interactions on vesicular-arbuscular mycorrhizal infections. i. host and non-host plants grown together

Abstract: Summary Mycorrhizal infections formed by different endophytes were examined in 10 crop species grown separately and in pairs in sterilized and unsterile soils. No infection was observed in cabbage, kale, rape or swede (in the supposedly non-mycorrhizal family Cruciferae) and only traces were seen in sugar beet (supposedly non-mycorrhizal Chenopodiaceae) when these plants were grown alone. However, slight (< 5 %) infection (cortical mycelium and vesicles, but no arbuscules) developed in some when a mycorrhizal host plant was present and there were many clumps of endophyte mycelium on their root surfaces, usually attached to entry points which had often aborted. Glomus fasciculatus‘E3’ was a more infective endophyte than Gigaspora margarita. Infection was usually well developed in the host plants barley, lettuce, maize, potato and onion. It was depressed only in a few pairs but no more by the presence of a ‘non-host’ plant than by a host plant. The results suggest that the barriers to mycorrhizal infection in ‘non-hosts’ are intrinsic and more probably related to characteristics of the root cortex or epidermis than to any infection-inhibiting factors that might be released in root exudates.

Relation of internal phosphorus concentration and plant weight in plants infected by vesicular‐arbuscular mycorrhizas

Abstract: Summary Our own results and a search of the literature have shown that shoots of plants infected with vesicular-arbuscular mycorrhiza normally contain higher internal concentrations of P than those of uninfected plants of equal size, over wide ranges of external P supply and of host plants. Increased demand for carbon by infected roots is a possible explanation for this, and simple graphical methods of estimating the resulting dry wt loss are suggested.

Effects of waterlogging at different stages of development on the growth and yield of winter wheat

Abstract: The response of winter wheat to waterlogging at different stages of growth outdoors was studied for 3 years using lysimeters containing undisturbed monoliths of sandy loam and clay soils. The treatments were selected as the most extreme likely to occur in field conditions in Britain, i.e. waterlogging to the soil surface for up to 16 days in October, 42 days in January and February and 6 days in May. Waterlogging in midwinter was common to all experiments. Yield losses from mid-winter waterlogging ranged from 15% when yields were heavy (10 t ha−1), to nil when yields were light (3-4 t ha−1) after the plants had been affected by frost damage in late winter and by take-all. Winter wheat was most sensitive to waterlogging after germination but before emergence. At this stage, 16 days waterlogging killed all seedlings and 6 days waterlogging depressed plant populations to 12% (clay) and 38% (sandy loam) of the control. However, there was vigorous compensatory growth in the remainder of the growing season and yield was only depressed to about 82% of the control. When the crop was waterlogged at any stage after emergence plant populations were not affected; however, winter waterlogging treatments usually depressed shoot numbers and, to a lesser extent, ear numbers at harvest. Shoot survival under waterlogged conditions seemed related to nitrogen availability in the soil. The amount of ‘take-all’ (Gaeumannomyces graminis var. tritici) was increased by waterlogging.

Proteins at liquid interfaces. V. Shear properties

Abstract: The shear rheological properties of films of β-casein, bovine serum albumin (BSA), and lysozyme adsorbed at air-water and oil-water interfaces have been measured with a surface viscoelastometer. The globular proteins BSA and lysozyme form viscoelastic films when adsorbed to both air-water and oil-water interfaces whereas the disordered β-casein molecule exhibits viscoelastic properties which are so low that they are only just detectable. The viscoelastic properties are related to mechanical models comprising elastic springs and viscous dashpots. The viscoelastic properties exhibited by BSA and lysozyme are dependent upon the surface concentration and reach maximum values at about saturation monolayer coverage. Lysozyme films exhibit greater resistance to shear than BSA films at similar surface concentrations; the maximum surface viscosity coefficient, η 0 , for lysozyme at the air-water interface is greater than 10 4 mN s m −1 while the equivalent figure for BSA is 4 × 10 2 mN s m −1 . This difference results from the greater cohesion and degree of structure of lysozyme films. The viscoelastic properties of BSA films are maximum at the isoelectric point of the proteins. The rheological properties of the films at air-water and oil-water interfaces are compared; the unit area of flow and activation energy of flow are larger at the latter interface. The adsorbed, surface denatured protein film can be considered as a thin (∼100 A) protein gel layer.

Translocation and transfer of nutrients in vesicular-arbuscular mycorrhizas. III. Polyphosphate granules and phosphorus translocation

Abstract: Summary X-ray microanalysis has confirmed, and measured, the phosphorus content (0·03 g cm-3) of cytochemically-demonstrated polyphosphate granules in onion mycorrhizas. The volume occupied by the granules measured from stereoscopic high-voltage electron micrographs of thick sections was 0·8 % of the fungal volume, and cytoplasmic streaming rates of the extra-matrical mycelium in soil measured in the light microscope were around 12·6 cm h-1. From these data a flux rate of about 2·7 × 10-8 mol P cm-2 s-1 has been calculated, which fulfils the hypothesis that phosphorus is translocated in the fungus by means of the transport of polyphosphate granules by cytoplasmic streaming.

The Extraction, Solubility, and Characterization of Two Groups of Barley Storage Polypeptides

Abstract: This paper reports further studies on the characteristics of the storage protein fraction (hordein) of barley. Hordein consists of two groups of polypeptides (termed 'B' and 'C') coded by two separate but linked loci. Whereas the 'C' polypeptides are readily soluble and extracted in 60% (v/v) ethanol at room temperature, the 'B' group is more soluble in, and therefore more efficiently extracted by, 50% (v/v) propan-l-ol or 45% (v/v) propan-2-ol at elevated temperatures and in the presence of 2-mercaptoethanol. However, the most efficient conditions for hordein extraction (50% propan-l-ol + 2% (v/v) 2-mercaptoethanol at 60 °C) also extract some contaminating non-hordein polypeptides resulting in an apparently increased lysine content of the hordein fraction. Amino acid analysis of the purified 'B' and 'C' hordein groups shows that, whereas 'C' hordein contains more glutamate + glutamine, proline, and phenylalanine than 'B' hordein, it contains only traces of lysine and sulphur amino acids in contrast to 'B' hordein which contains 0-5% lysine 0-6% methionine, and 2-5% cysteine. Equilibrium sedimentation analyses carried out on the purified 'B' and 'C' groups indicates that the preparations were reasonably monodisperse with molecular weights of approximately 32 000 and 52 000 respectively. These values are considerably lower than those previously determined by SDS-PAGE.1

The effects of grinding on microbial and non-microbial organic matter in soil.

Abstract: Summary Grinding more than doubled the respiration rate of two silt loam soils, one arable and one grassland. The increases were smaller when the grinding treatment was given to portions of soils that had previously been fumigated with CHCI3and incubated, a treatment that greatly decreased microbial biomass. The results indicate that the flush of decomposition caused by grinding was in part derived from killed organisms and in part from enhanced decomposition of non-biomass sections of the soil organic matter. Grinding killed about a quarter of the biomass in both soils. Carbon from killed organisms accounted for a quarter of the extra CO2–C evolved after grinding in the arable soil and almost half in the grassland soil. The extra non-biomass organic matter decomposing after grinding amounted to about 0.5% of the soil organic carbon in both soils. This non-biomass material rendered decomposable by grinding had a higher C/N ratio than the organic matter decomposing in unground soil.

Uptake of pesticides from water and soil by earthworms

Abstract: The uptake of pesticides by earthworms from aqueous solutions was examined and shown to be a reversible physical process. Measurements of distributions of pesticides between aqueous solutions and worm solids showed that adsorption coefficients were related to octanol-water distribution coefficients, as are soil-water distributions. From these relationships it was calculated that concentration factors of stable chemicals in earthworms from soil should be similar, except for polar substances which penetrate poorly, and be determined mainly by the soil organic matter content. Examination of uptake from soils indicated that the calculated concentration factors are unlikely to be achieved because of slow diffusion of chemicals in soils and because of metabolism in the soil or the worm.

Effect of vesicular-arbuscular mycorrhizal fungi on the relations of plant growth, internal phosphorus concentration and soil phosphate analyses

Abstract: Summary The effect of infection by vesicular-arbuscular mycorrhiza on the predictive value of soil analysis for available P was tested in a glasshouse experiment. Leeks (Allium porrum) were grown on ten Rothamsted soils with a wide range of initial NaHCO3-soluble P, each of which also received 5 levels of added P. Soils were partially sterilized with 1 Mrad of γ-radiation, or left untreated; plants on sterilized soil were infected with yellow-vacuolate endophyte (Glomus mosseae) or left non-mycorrhizal. The NaHCO3-soluble P in the soils was measured 5 days after phosphate addition. Yields from all P levels on all soils were plotted against soil NaHCO3-soluble P content and separate smooth response curves were obtained for non-infected and artificially-infected plants. Infection increased yield only on soils with less than 100 mg P kg−1. In contrast, naturally-infected plants gave no clearly defined response curve to P, and on three soils the yields were consistently low. These soils gave very low natural infections and had low spore densities probably due to the cropping history of the sites. Artificially-infected plants had much higher shoot P concentrations than did uninfected plants of similar dry weight, over a large range of soil phosphate levels; this effect was also noted with the endophyte G. fasciculatus. Naturally-infected plants showed a poor relationship between shoot P concentration and yield.

N-terminal amino acid sequence homology of storage protein components from barley and a diploid wheat

Abstract: Wild barley (Hordeum spontaneum) and the wild diploid wheat Triticum boeoticum were possibly the first plants cultivated by early man1, giving rise to the domesticated forms Hordeum vulgare L. and Triticum monococcum L. In addition, T. boeoticum may have contributed the A genome to polyploid wheats, including common bread wheat (Triticum aestivum)2 which is a hexaploid with genome composition ABD. Hordeum seems to be the older genus, having diverged from some common ancestor before the divergence of Triticum and other genera of the subtribe Triticinae3. Prolamins constitute the major storage protein fraction of both barley and wheat; they are located in the endosperm of the caryopsis and are soluble in alcohol–water solutions4. Barley and wheat prolamins (hordeins and gliadins, respectively) contain large amounts of glutamine and proline, which together make up 50–75 mol per cent of total amino acids4,5. The hordeins and gliadins are complex mixtures of components6–8 that seem to be encoded by clusters of duplicated genes that have diverged to produce many distinguishable protein components. Despite the complexity of the gliadin mixture, the components retain considerable homology in their N-terminal region9,10 and this has been reported for zeins, the prolamins of maize (Zea mays)11, as well. Here, we report that a purified C-hordein component from barley is homologous in amino acid sequence with a purified ω-gliadin component from T. monococcum at 23 of 27 residues at the N-terminus. This result is in accord with the close relationship between the two species and indicates that, despite the propensity of prolamin genes to tolerate mutations, a significant portion of their sequences can be conserved over a period of time, which, although not accurately known, probably amounts to millions of years.

An analysis of human decision-making in cement kiln control and the implications for automation

Abstract: This paper describes the investigation into the control skills of cement kiln operators with a view to modelling these skills by a fuzzy algorithm. The operators' strategies were studied by observing and making a detailed record of the operators' behaviour as they controlled the kiln. Analysis of the observational record suggested that many aspects of the operators' control behaviour could be modelled by a threshold logic controller. An improvement to the threshold model was attempted by comparing the operators' performance with the performance produced by a set of prescriptive control rules. Although the prescriptive rules were found to be an inadequate model of the kiln operators, analysis indicated that the rules had the potential to produce better kiln control. The implementation of the prescriptive rules as a fuzzy controller is discussed.

Stress and Work: A Review and Theoretical Framework, I

Abstract: There is a large literature devoted to the stresses and strains of work and work‐related activities. This research effort shows no sign of abating. The aim of this paper is to highlight and discuss several centrally important questions and assumptions in the nature of this research which, in our view, require more careful consideration in future work.

The degradation of aldicarb and oxamyl in soil

Abstract: The breakdown of oxamyl was studied in three downland chalk soils, a peat loam, a sandy loam, and the same sandy loam modified by adding peat. The kinetics of aldicarb degradation via its sulphoxide and aldoxycarb (aldicarb sulphone) were also studied in these two sandy loam soils. All the reactions followed first-order kinetics, the reaction being faster in the original than in the modified sandy loam. Rates of reaction were slower at low moisture contents, and decreased markedly when the temperature was reduced from 10 to 5°C though less so than from 15 to 10°C.

Contractile and relaxant actions of prostaglandins on guinea-pig isolated trachea

Abstract: 1 The effects of 12 prostaglandins on guinea-pig isolated trachea have been examined in the presence of indomethacin. Two series of experiments were carried out, the first on preparations without tone ('zero tone'), and the second on preparations with tone induced with acetylcholine ('high tone'). 2 The compounds tested fell into two groups. The first, comprising prostaglandins F1 alpha, F2 alpha, F2 alpha acetal, I2 and Wy 17186, contracted both zero and high tone preparations. The second, comprising prostaglandins A1, A2, B1, B2, E1, E2 and F2 beta, contracted zero, but relaxed high tone preparations. Responses to the second group of compounds are probably the resultant of their contractile and relaxant actions. 3 The order of potency for contracting zero tone preparations was prostaglandin E (PGE) greater than F = 1 = Wy 17186 greater than B greater than A, 2-series compounds being 5 to 18 times more potent than 1-series compounds. 4 The order of potency for relaxing high tone preparations was PGE greater than F beta greater than B greater than A greater than Wy 17186 greater than F alpha = I = 0. There was little difference between the potency of 1- and 2-series compounds. 5 The possible relevance of these results to the interpretation of the effects of prostaglandins on human airways is discussed.

Detector for an optical-fiber acoustic sensor using dynamic holographic interferometry

Abstract: It is shown that the acoustically induced phase modulation of coherent light propagating within a multimode optical fiber may be linearly detected by an interferometer employing an unmodulated replica of the fiber beam as the reference. It is proposed that a dynamic hologram provide such a reference. This technique allows a performance comparable with that of a monomode interferometric sensor to be obtained, but with considerably relaxed alignment tolerances.

Latin Square designs in field experiments involving insect sex attractants

Abstract: . 1Interactions between insect sex attractant traps are of ecological interest in themselves, but may cause problems in field experiments in which attractants, or control measures, are compared quantitatively. 2Some of these problems are solved by experimental designs based on the Latin Square. 3The applicability of the designs to research involving comparison of attractants, effectiveness of control measures and attractant trap interactions is discussed, and examples are given with field data. 4Efficiencies of different designs are compared using data from fifteen experiments. 5Disadvantages and extensions of the design are discussed. 6Latin Square designs are simple, practical, and usually more efficient than other designs.

A potential application of aphid alarm pheromones

Abstract: (E) 13 farnesene has been reported to be the main component of the alarm pheromone of many species of aphids (Bowers et al., 1972; Edwards et al., 1973; Wientjens et al., 1973; Pickett & Griffiths, 1980). Bowers et al., (1972) suggested that this compound could also be used to provide a novel method of control by dispersing aphids from their feeding sites. However, Calabrese & Sorensen (1978) reported that aphids dispersed by their alarm pheromone mostly recolonise the plant surfaces within an hour of exposure. Another approach was tried by Hille Ris Lambers & Schepers (1978) who attempted unsuccessfully to use a slow release formulation of (E) 13 farnesene to restrict virus spread by aphids in potatoes. A third suggestion (Edwards et al., 1973) was that alarm pheromone might enhance effectiveness of insecticidal sprays by increasing mobility of aphids and thereby increasing contact with the toxicant, but this has so far not been demonstrated. Increased contact with pesticide could enhance the contribution that contact action makes to the effectiveness of systemic sprays or make the use of purely contact poisons more effective. Such an approach may now be more valuable because aphids are developing resistance to present insecticides (Hrdy, 1975; Sawicki & Rice, 1978). The ability of synthetic pheromone to improve effectiveness of a contact insecticide was tested in the laboratory using cultures of 50--70 insecticidesusceptible Myzus persicae (Sulz.), mainly 3rd--4th instar, bred on small plants of Chinese cabbage (Brassica pekinensis Rupr.). There were four treatments (Table I) each with six replicates. Synthetic alarm pheromone was applied in the vapour phase in air slowly released from a glass syringe (25 ml of saturated air per plant, corresponding to ca. i.5 lag (E) 13 farnesene) immediately before each plant was placed in a I-m 3 box and sprayed from above with 0.3 ml of either water or insecticide. The insecticide used for these laboratory tests was 0.05% permethrin (\"Ambush\", ICI) because it has good contact but no systemic action. (Permethrin would not be suitable for field tests against resistant aphids because, as Sawicki & Rice, 1978, ha~,e shown, organophosphate-resistant aphids also lack susceptibility to pyrethroids). Numbers of aphids on control plants increased slightly (Table I) due to adults giving birth. Colonies of aphids treated with pheromone and water showed a significant decrease in numbers at 24 hr, indicating that not all aphids that left the plants had returned even though return was not artificially prevented. Although this result differs somewhat from the findings of Calabrese & Sorensen (1978), the effect is too smal/to be of practical value. Insecticide alone gave a relatively poor kill (38% decrease in population); the aphids were undisturbed by this treatment.

Stability of insecticide resistance in the peach-potato aphid, Myzus persicae (Sulzer)

Abstract: Anholocyclic Myzus persicae (Sulz.) from the glasshouse and field can be classified into six variants, each with a characteristic carboxylesterase activity and consequent resistance to carbamate and organophosphorus insecticides. Overlapping activity distributions prevent unequivocal identification of an individual from measurements of its enzyme activity, but this may be done by cloning and measuring the frequency distribution of the enzyme activity in its progeny. Although each of the four lowest esterase variants has a frequency distribution with a single peak, only the susceptible (USLL) is best described by a single Normal distribution. Those of the other three clones (MSIG, French R and T1V) correspond better with two Normally-distributed components. However, these are not well separated and the lower component accounts for only 10-25% of the individuals. The very resistant clones from glasshouses have higher mean activities but with very broad distributions covering the whole range observed in this aphid. These broad distributions have peaks corresponding to those of the less resistant variants and arise from the appearance at each generation of a small proportion of individuals with much less active enzyme than their parents. Careful monitoring of the changes in activity between parents and offspring of the most resistant variant (clone G6) showed that complete loss of resistance can occur either in a single step or over several generations, and that below a threshold value, reversion to higher levels is very rare. Such reversion could only be detected by selection, with insecticide, of large clonal populations from an individual that had lost activity. High esterase activity was not stabilised by breeding for 16 generations only from individuals with high esterase activity, and is probably maintained in glasshouses by continuous exposure to insecticides. Spontaneous loss of esterase activity and resistance was observed only in glasshouse populations.