Showing papers by "The Hertz Corporation published in 1977"

Studies on the decomposition of plant material in soil. v. the effects of plant cover and soil type on the loss of carbon from14c labelled ryegrass decomposing under field conditions

Abstract: Summary Ryegrass uniformly labelled with 14C was allowed to decompose for 10 years under field conditions in a range of contrasting soils. The amount of organic matter already in a soil had no effect on the retention of labelled C by that soil, nor had a variation in soil pH of from 4.9 to 8.1. Decomposition was initially slower in a strongly acid soil (pH 3.7) but by the end of 5 years the difference between this soil and the others had almost disappeared. The more clay in a soil, the greater the retention of labelled C over the whole 10 year period; this was true of both strongly acid and near-neutral soils. More labelled organic matter was leached from a soil containing 7.6% clay than from one with 17.5% clay, but the amount thus lost was insufficient to account for the difference in retention of C by the two soils. The decomposition of labelled plant material was faster in bare soil than in soil growing grass but the ‘protection’ thus given to the labelled C by the growing grass ended when the grass was removed. In bare soil about one third of the labelled ryegrass C was left after one year but thereafter decomposition became very much slower and about one eighth of the labelled C still remained in the soil after 10 years. The decay curve can be represented by a two compartment model, in which about 70% of the ryegrass C decomposed by a first order process of half life 0.25 years and the remainder by a similar process of half-life 8 years.

A Reformulation of Linear Models

Abstract: SUMMARY Dissatisfaction is expressed with aspects of the current exposition of linear models, including the neglect of marginality, unnecessary differences between models for finite and infinite populations, failure to distinguish different kinds of random terms, impositon of unnecessary and inconsistent constraints on parameters, and lack of an adequate notation for negative components of variance. The reformulation, exemplified for crossed and nested classifications of balanced data, and for simple orthogonal designed experiments, is designed to integrate finite and infinite populations, random and fixed effects, excess and deficit of variance, to avoid unnecessary constraints on parameters, and to lead naturally to interesting hypotheses about the model terms.

An International Scheme for Identifying and Classifying Pathotypes of Potato Cyst-Nematodes Globodera Rostochiensis and G. Pallida

Abstract: Following joint tests in the Netherlands, Germany and the United Kingdom a new scheme is proposed for naming pathotypes of potato cyst-nematodes. Pathotypes of Globodera ( = Heterodera) rostochiensis and G. pallida are designated separately using a simple nomenclature Ro1 to Ron for G. rostochiensis and Pa1 to Pan for G. pallida. Currently seven clones are used to differentiate five pathotypes of G. rostochiensis and three of G. pallida. Several of the pathotypes recognised in the British, Dutch and German National Schemes are the same. Results of pathotyping tests may show considerable variation; adequate replication and standardisation of method are essential. With an internationally used scheme it is highly desirable that new pathotypes or differential clones are added only after testing at Institutes in several countries.

A simple computer model for leaching in structured soils

Abstract: Summary A layer model for the movement of solutes in soil has been developed in which, as a working approximation, the soil solution is partitioned into mobile and retained phases. Only the mobile solution is displaced during water movement, and equilibrium is assumed to be established between the mobile and retained phases when flow ceases, giving holdback of solute. The model permits the displacement of the mobile solution through an indefinite number of layers when large amounts of rain fall. It can be assumed either that water and solute are stored in the bottom layer and can be withdrawn up the profile by evaporation or that they drain from the bottom layer. Predicted soil nitrate concentrations agreed reasonably well with those measured in a field experiment and indicated some sensitivity to layer thickness. The capacity of the model to predict concentrations in drainage is demonstrated.

The properties of a carboxylesterase from the peach-potato aphid, Myzus persicae (Sulz.), and its role in conferring insecticide resistance.

Abstract: Carboxylesterases from different strains of Myzus persicae were examined to try to understand their contribution to insecticide resistance. Preliminary evidence that they are involved comes from the good correlation between the degree of resistance and the carboxylesterase and paraoxon-degrading activity in aphid homogenates. Furthermore the carboxylesterase associated with resistance could not be separated from the insecticide-degrading enzyme by electrophoresis or ion-exchange chromatography. Homogenates of resistant aphids hydrolysed paraoxon 60 times faster than did those of susceptible aphids, yet the purified enzymes from both sources had identical catalytic-centre activities towards this substrate and also towards naphth-1-yl acetate, the latter being hydrolysed by both 2×106 times faster than paraoxon. These observations provide evidence that the enzyme from both sources is identical, and that one enzyme hydrolyses both substrates. This was confirmed by relating the rate of paraoxon hydrolysis to the rate at which paraoxon-inhibited carboxylesterase re-activated. Both had the same first-order rate constant (0.01min−1), showing clearly that the hydrolysis of both substrates is brought about by the same enzyme. Its Km for naphth-1-yl acetate was 0.131mm, and for paraoxon 75pm. The latter very small value could not be measured directly, but was calculated from substrate-competition studies coupled with measurements of re-activation of the diethyl phosphorylated enzyme. Since the purified enzymes from resistant and susceptible aphids had the same catalytic-centre activity, the 60-fold difference between strains must be caused by different amounts of the same enzyme resulting from mutations of the regulator gene(s) rather than of the structural gene.

The measurement and characterisation of voids in soil thin sections by image analysis. part i. principles and techniques

Abstract: Summary The introduction of the image analysing computer (Quantimet 720) makes possible the rapid and accurate measurement of components in thin sections and extends the range of measurements possible. Two techniques for presenting material for analysis are outlined. Models are used to demonstrate the measurement of size, irregularity and orientation of components and their discrimination according to shape.

A colorimetric method for estimating vesicular-arbuscular mycorrhizal infection in roots

Abstract: A colorimetric method measuring the conversion of fungal chitin to glucosamine has been used to estimate the intensity of vesicular-arbuscular mycorrhizal infection in roots. The technique has been used successfully with four plant genera and with four different endophytes.

Observations On Fungal Parasites of Females and Eggs of the Cereal Cyst-Nematode, Heterodera Avenae, and Other Cyst Nematodes

Abstract: Most populations of the cereal cyst-nematode are parasitised by fungi killing females and eggs. The life history of an Entomophthora-like fungus, which kills females and causes the breakdown of the cuticle preventing cyst formation, is described. This fungus attacks other cyst-nematodes but not Globodera rostochiensis. A method is described for estimating the number of diseased eggs in females and cysts. Verticillium chlamydosporium was the most frequently observed egg parasite; it killed 50% of the eggs in females on barley roots in July in a field trial. Tarichium auxiliare and Cylindrocarpon destructans were found more frequently in soils where the nematode failed to multiply than in those where it increased but were not considered important as few females were infected. Similar numbers of new females were produced in soils where populations multiply or decline but in decline soils many failed to form cysts and few healthy eggs were produced.

A Review of the Distribution and Biology of the Potato Cyst-Nematodes Globodera rostochiensis and G. pallida

Abstract: Potato cyst-nematode species are believed to have evolved in South America but now have a worldwide distribution and can be major and persistent pests except in the warmest soils. Both species contain pathotypes and their correct identification, although difficult, is important when planning control with resistant potatoes. Some closely related and very similar species are of minor economic importance. Resistant cultivars available at present are effective against only some pathotypes and except where high crop values make use of nematicides economic, it is important to combine extended crop rotation with such cultivars.

Genetics of resistance of houseflies (Musca domestica L.) to pyrethroids. I. Knock-down resistance

Abstract: Knock-down resistance in Musca domestica, which provides cross-resistance between DDT and pyrethroids, has been genetically separated from three different resistant populations. After careful purification of each factor, the cross-over rates between them and the visible mutants brown body and green eye were estimated. This indicated that these factors are probably identical. The influence and implications of the knock-down resistance factor, kdr, on the total resistance of populations that include it are briefly discussed.

Hatching of Cyst-Nematodes

Abstract: This review primarily covers literature on the hatching of cyst-nematodes that has appeared since 1971. The section on physical factors which influence hatching includes the effects of temperature, moisture, aeration and seasonal effects especially in relation to diapause. Research dealing with chemical stimulation and inhibition of hatching is also reviewed and the mechanism of hatching is discussed with particular reference to Globodera rostochiensis.

Studies on the decomposition of plant material in soil .IV. The effect of rate of addition

Abstract: Summary Different amounts of ryegrass roots and tops, both uniformly labelled with 14 C, were mixed with soil and allowed to decompose for 155 days under controlled conditions in the laboratory at 25°C. Initially the roots decomposed more slowly than the tops but by 155 days this difference had disappeared. About a third of the added plant C remained in the soil at the end of 155 days, about as much as when the same plant materials were incubated in the same soils for 6 months in the field. To a first approximation, the amount of labelled CO2–C evolved was directly proportional to the amount of labelled plant C added. This held throughout the incubations. However, a slightly smaller percentage of the added plant C was evolved with small additions than with large, although this effect was on the limits of detection. Slightly more labelled plant C was retained in a soil rich in organic matter (2.43% C) than in an otherwise similar soil with less organic matter (0.97% C).

Invasive and developmental processes of Entomophthora species infecting aphids

Abstract: Entomophthora aphidis Hoffmann and E. thaxteriana (Petch) Hall & Bell on Acyrthosiphon pisum Harris, and E. fresenii (Nowakowski) Gustafsson and E. planchoniana Cornu on Aphis fabae Scopoli penetrate the cuticle at any point, probably by enzymic and mechanical processes. Only E. fresenii forms an appressorium. Hyphae or hyphal bodies of each fungus first invade the haemocoel where individual blood cells appear to engulf some but do not agglomerate and encapsulate them; each species invades the solid tissues sequentially, with slight differences between fungal species, but all invade sclerotized tissues and embryos last, often after the host dies. Each pseudocystidium of E. aphidis develops from a swollen hyphal body and breaches the aphid cuticle allowing the surrounding conidiophores to emerge. These, and the conidiophores of E. planchoniana and E. thaxteriana, begin to emerge in groups, but eventually those of all species cover the cuticle in an even layer. Weakly differentiated rhizoids sometimes develop around the mouthparts of aphids killed by E. thaxteriana; rhizoids of E. aphidis develop from greatly swollen hyphal bodies, and the compound ones of E. planchoniana develop from bundles of elongated hyphal bodies in the thorax and abdomen of the host; rhizoids of both of these species sometimes emerge before the aphid dies.

The measurement and characterisation of voids in soil thin sections by image analysis. part ii. applications

Abstract: Summary Image analysis was used to measure and characterise the voids in two sets of soil samples; (i) a surface water gley soil of the Deighton series and (ii) soils from a compaction experiment. The results show that the Deighton soil contains two impervious horizons separated by a much more porous horizon. In all the horizons most of the pore space is due to pores >180μm diam. In the case of the soils from the compaction experiment compaction was shown to change the shape, orientation and size distribution of the pores considerably. The range of measurements demonstrates that image analysis is applicable to several areas of soil research.

Crop Protection: A Consideration of the Effectiveness and Disadvantages of Current Methods and of the Scope for Improvement

Abstract: Ideally crop protection should prevent damaging effects of pests, diseases and weeds economically, safely and without harming the environment or inducing subsequent control problems. Present methods, based mainly on pesticides and resistant crop varieties, control many damaging organisms effectively but have important limitations. Vulnerability to the emergence of tolerant strains of pest or pathogen is probably the most severe; chemical methods are also often insufficiently selective and very wasteful. Dependence on these methods will continue, however, and it is therefore essential to seek ways of minimizing their deficiencies. The prospects for improvement are discussed in relation to the need for better intelligence about infestations and their consequences, the need to ensure that control measures remain effective and the need to improve the efficiency of utilization of crop protection agents. Implementation of the suggestions for improvement could require fundamental changes in the organization of crop protection practices.

Re‐examination of the linear glutenin hypothesis

Abstract: The hypothesis that glutenin molecules consist of polypeptide chains joined by SS bonds into linear concatenations, instead of into branching giant molecules, is further examined. The concept that secondary forces can build up sequentially to produce appreciable tension in the molecules appears to fit the facts better than the idea that entangled molecules behave like a knot, which predicts a relation between tenacity and mol.wt. not observed for other high polymers. Work hardening arises because orientation makes the most effective use of secondary forces, the molecules being aligned so that they overlap by substantial fractions of their lengths. SS interchange in dough not only relieves stress but controls the average length of concatenations. Viscous flow depends predominantly on molecular slip, but is assisted by mechanical fission and SS interchange. In a resting dough mechanical scission is absent and SS interchange makes a relatively greater contribution to stress relaxation. Mechanical scission will not occur in terminal segments of concatenations. In an overworked dough, the length of many concatenations is at least halved by mechanical scission, greatly reducing the resistance. The predicted level of SH groups produced by mechanical fission is of a similar order to an experimental value quoted in the literature.

An example of cross-resistance to pyrethroids in DDT-resistant Aedes aegypti

Abstract: Comparisons of the susceptibility of several strains of adult Aedes aegypti were made. Mosquitoes from Bangkok and Jakarta were found to be highly resistant to DDT and resistant to pyrethroids relative to a laboratory strain. A strain from Singapore, where less DDT has been used, was susceptible to DDT and pyrethroids. Two strains from the Caribbean had LC50 values to DDT 3 times that of the reference strain while the LC50 values against bioresmethrin synergised with piperonyl butoxide were 1 1/2 times raised. Another two strains from central Africa were 2 times tolerant of DDT and 1 1/2 times tolerant of bioresmethrin plus piperonyl butoxide. Agents which block DDT-dehydrochlorinase, esterases and oxidases each caused small increases in the mortality of the Bangkok strain due to DDT and bioresmethrin as well as augmenting toxicity to the susceptible reference strain. It is tentatively suggested that resistance in the Bangkok strain is due to a combination of the actions of these and perhaps other resistance mechanisms.

The particle-size distribution in wheat endosperm starch

Abstract: Particle-size distribution in samples of endosperm starch from six types of wheat was determined by microsieving. The size distribution of two of these samples and of six others was analysed automatically by the Coulter Counter and Quantimet. The results indicate that more than one-third of the total weight of starch is contributed by granules with diameters less than 10 μm. This value exceeds, by a wide margin, the proportion generally attributed to granules of this size.

Electron-paramagnetic-resonance studies of leghaemoglobins from soya-bean and cowpea root nodules. Identification of nitrosyl-leghaemoglobin in crude leghaemoglobin preparations.

Abstract: 1. Leghaemoglobins from soya-bean (Glycine max) and cowpea (Vigna unguiculata) root nodules were purified by chromatography on DEAE-cellulose phosphate columns at pH8.0 and pH5.8, to avoid the relatively low pH (5.2) commonly used to purify these proteins. 2. E.p.r. (electron-paramagnetic-resonance) spectra of the fluoride, azide, hydroxide and cyanide complexes of these ferric leghaemoglobins were very similar to the spectra of the corresponding myoglobin derivatives, indicating that the immediate environment of the iron in leghaemoglobin and myoglobin is similar, an imidazole moiety of histidine being the proximal ligand to the haem iron [cf. Appleby, Blumberg, Peisach, Wittenberg & Wittenberg (1976) J. Biol. Chem. 251, 6090–6096]. 3. E.p.r. spectra of the acid-metleghaemoglobins showed prominent high-spin features very near g=6 and g=2 and, unlike myoglobin, small low-spin absorptions near g=2.26, 2.72 and 3.14. The width of the g=6 absorption derivative at 10–20K was about 4–4.5mT, similar to the value for acid-methaemoglobin. In contrast, a recently published (Appleby et al., 1976) spectrum of acid-metleghaemoglobin a had less high-spin character and a much broader absorption derivative around g=6. 4. E.p.r. spectra of ferric leghaemoglobin nicotinate and imidazole complexes suggest that the low-spin absorption near g=3.14 can be attributed to a trace of ferric leghaemoglobin nicotinate, and those near g=2.26 and 2.72 are from an endogenous dihistidyl haemichrome. 5. A large e.p.r. signal at g=2 in all samples of crude leghaemoglobin was shown to be from nitrosyl-leghaemoglobin. A soya-bean sample contained 27±3% of the latter. A previously unidentified form of soya-bean ferrous leghaemoglobin a was shown to be its nitrosyl derivative. If this is not an artifact, and occurs in the root nodule, the nitrosyl radical may interfere with the function of leghaemoglobin.

Polarographic Study of Ammonia Assimilation by Isolated Chloroplasts

Abstract: Illuminated pea ( Pisum sativum ) chloroplasts catalyze (ammonia plus α-ketoglutarate [α-KG])-dependent O 2 evolution at rates which are commensurate with other estimates of the flux of assimilated nitrogen (mean of eight determinations, 8.3 μmole per mg chlorophyll per hour, sd 2.4). The reaction was usually initiated with 1 mm ammonia after preincubating chloroplasts in the presence of α-KG, ADP, pyrophosphate, and MgCl 2 . Progressive increases in ammonia concentration gave V max /2 at 0.2 mm (approximately) and V max at about 1 mm. Higher concentrations were inhibitory; at 7 mm the rate was again about V max /2. The highest ratio of O 2 evolved per mol of ammonia supplied was 0.36. The (ammonia plus α-KG)-dependent reaction was inhibited by methionine sulfoximine, azaserine, and aspartate in the presence of amino-oxyacetate but not by amino-oxyacetate alone and not by l-glutamate. The rate of O 2 evolution in the presence of 1 mm ammonia and 2.5 mm α-KG was increased only slightly by addition of 5 mm glutamine. Similarly, the rate of O 2 evolution in the presence of 5 mm glutamine and 2.5 mm α-KG was increased only slightly by addition of 1 mm ammonia. The results are attributed to the incorporation of ammonia via glutamine synthetase and reductive transamination of the glutamine formed by photosynthetically coupled glutamate synthase using α-KG as the amino acceptor. Several lines of evidence rule out the possibility that photosynthetically coupled glutamate dehydrogenase is involved.

A polarographic study of glutamate synthase activity in isolated chloroplasts.

Abstract: Illuminated pea ( Pisum sativum ) chloroplasts actively catalyzed (glutamine plus α-ketoglutarate)-dependent O 2 evolution (average of 12 preparations 10.6 μmole mg chlorophyll per hour). The reaction was specific for glutamine and α-ketoglutarate; concentrations of 0.2 mm α-ketoglutarate and 0.6 mm glutamine, respectively, effected half-maximum rates of O 2 evolution. The reaction was inhibited by 3-(3,4-dichlorophenyl)-1-1-dimethylurea and did not occur in the dark. After osmotic shock chloroplasts did not catalyze O 2 evolution. The reaction was inhibited by azaserine and glutamate but not by 10 mm ammonia, 2.5 mm methionine sulfoximine, or 5 mm amino-oxyacetate; addition of amino-oxyacetate together with aspartate inhibited O 2 evolution. Arsenate (3 mm) enhanced O 2 evolution. The highest molar ratio for O 2 evolved per mole of α-ketoglutarate supplied was 0.40; the corresponding values for glutamine in the absence and presence of 3 mm arsenate were 0.20 and 0.24, respectively. The (glutamine plus α-ketoglutarate)-dependent O 2 evolution is attributed to photosynthetically coupled glutamate synthase activity and the activity is sufficient to account for the assimilation of inorganic nitrogen. The low molar ratio for glutamine is discussed. Chloroplasts also catalyzed (aspartate plus α-ketoglutarate)-dependent O 2 evolution but this reaction was inhibited by 5 mm amino-oxyacetate and it was insensitive to azaserine and methionine sulfoximine. This reaction was attributed to transaminase and photosynthetically coupled malate dehydrogenase activities.

Ozone concentrations in South-East England during the summer of 1976

Abstract: Surface ozone concentrations at five sites in South-East England were measured during the heat wave of 1976 from 22 June to 12 July. At all sites peak hourly concentrations were the highest ever recorded in the UK and the elevated levels persisted for periods longer than any previously measured. Some discussion of the significance of the results is given together with an analysis of back-track air mass trajectories in the context of oxidant formation in North-West Europe.

Insect-trapping Hairs on Potato Plants

Abstract: The ability of glandular hairs on the foliage of the wild potato species Solanum polyadenium and S. berthaultii to trap mite and insect pests is illustrated by scanning electron micrographs. Both potato species have hairs with four-lobed heads which release a sticky substance when ruptured. On S. polyadenium these hairs trapped aphids, Colorado beetle larvae and a leafhopper Javasella pellucida. S. berthaultii also has hairs with a sticky droplet at their tips; these hairs trapped such small pests as spider mites, thrips and larval mealybugs. Adult whitefly were not trapped because a powdery wax from the whiteflies coated the hairs. It is suggested that these glandular hairs could help protect potato crops by trapping many foliage pests, including disease vectors.