Showing papers by "The Hertz Corporation published in 1975"

Vesicular-arbuscular mycorrhizal infections in root organ cultures

Abstract: Vesicular-arbuscular mycorrhizal infections, similar to those formed in plants with leaves, have been established for the first time in clover root organ cultures. These infections are most easily established in roots grown on a modified White's agar medium but they can also form in liquid culture. The pH of the medium is a critical factor determining the initiation and spread of infection. White's medium inhibited spore germination and growing roots did not relieve this inhibition. Pre-germinated spores were therefore used as inoculum. The possible value of root organ cultures for the study of root: endophyte interactions is discussed in relation to studies of some obligate fungi.

The high‐ and low‐energy phosphate adsorbing surfaces in calcareous soils

Abstract: Summary The two-surface Langmuir equation was used to study P adsorption by 24 calcareous soils (pH 7.2-7.6; 0.8-24.2 per cent CaCO3) from the Sherborne soil series, which are derived from Jurassic limestone. High-energy P adsorption capacities (x″m) ranged from 140–345 μg P/g and were most closely correlated with dithionite-soluble Fe. Hydrous oxides therefore appear to provide the principal sites, even in calcareous soils, on which P is strongly adsorbed (x″m 6–51 ml/μg P). The low-energy adsorption capacities (x″m) ranged from 400–663 μg P/g and were correlated with organic matter contents and the total surface areas of CaCO3 but not with per cent CaCO3, pH, or dithionite-soluble Fe. Total surface areas of CaCO3 in the soils ranged from 4.0 to 8.5 m2/g soil. Low-energy P adsorption capacities agree reasonably with values (100 pg P/m2) for the sorption of phosphate on Jurassic limestones but phosphate was bonded much less strongly by soil carbonates (k″= 0.08–0.45 ml/μg P) than by limestones (k∼10.0 ml/μg P). Low-energy P adsorption in these soils is tentatively ascribed to adsorption on sites already occupied by organic anions (and probably also by bicarbonate and silicate ions) which lessen the bonding energy of co-adsorbed P.

Soil transect correlograms of north oxfordshire and their interpretation

Abstract: Summary In almost all soil surveys some attempt is made in the early stages to assess the scale on which the soil changes, and the information required is often obtained from transects. By recording soil properties at a constant close spacing on such transects methods of analysis, especially those devised for time series, data can be applied to reveal patterns of variation, and hence lead to rational mapping strategy. Correlograms, which show on average the relation of soil at one point to that at another, seem especially promising. The potential of time series analysis in soil survey was explored by measuring soil properties in three horizons in profiles at 10 m intervals along a transect across the Lower Jurassic outcrop in north Oxfordshire. Correlograms were computed for clay, silt, pH, CaCO3, colour value, and stoniness in each horizon. They showed that, for all the properties, the relation between sampling points weakened steadily over distances from 10 m to about 230 m. The average spacing between geological boundaries on the transect was also about 230 m, and outcrop lithology was inferred as one of the main sources of soil variation. The effect of rock type was eliminated by computing deviations of the original values from the means of the outcrops in which they occurred. Correlograms of these showed almost no relation between points more than 10 m apart; i.e. the only other major source of variation occurred within 10 m. In this instance mappable soil boundaries are likely to occur on average every 230 m, and sampling at a spacing closer than I15 m would be needed to detect them from profile inspection alone. Alternatively a map of the geological boundaries with descriptions of the soil for each map unit would constitute almost the best soil map that could be achieved in this area.

Glutamine and asparagine as nitrogen donors for reductant-dependent glutamate synthesis in pea roots.

Abstract: Glutamine, in the presence of alpha-oxoglutarate, stimulates nicotinamide nucleotide oxidation by crude extracts of pea roots and leads to a reductant-dependent formation of glutamate. Commercially available asparagine also stimulates nicotinamide nucleotide oxidation in the presence of alpha-oxoglutarate, but the reaction causing the stimulation can occur in the absence of a reductant, is inhibited by transaminase inhibitors, and is additive to the glutamine reaction. The asparagine used was found to be contaminated with aspartate. Repurified asparagine, chromatographically free of aspartate, did not stimulate the rate of nicotinamide nucleotide oxidation, and it is probable that the original stimulation was due to aspartate contamination. It is concluded that pea-root glutamine (amide)-alpha-oxoglutarate aminotransferase (glutamate synthase), in common with the enzyme in leaves, is specific for glutamine as the N donor and alpha-oxoglutarate as the N acceptor. The significance of the enzyme in conjunction with glutamine synthetase in the assimilation of nitrate by roots is discussed.

Studies of the acetylcholinesterase from houseflies (Musca domestica L.) resistant and susceptible to organophosphorus insecticides.

Abstract: Acetylcholinesterase from the heads of insecticide-resistant and -susceptible houseflies (Musca domestica L.) was studied in vitro. The enzymes could not be distinguished electrophoretically, and their behaviour on polyacrylamide-disc-gel electrophoresis was influenced by the presence of Triton X-100 in both the homogenate and the gels. In the absence of detergent, the acetylcholinesterase was heterogeneous, but behaved as a single enzyme when it was present. By analogy with studies of acetylcholinesterase from other sources, these observations were attributed to aggregation of the enzyme when not bound by membranes. The enzyme from resistant flies was more slowly inhibited than the susceptible enzyme, bimolecular rate constants (ki) differing by approx. 4-20-fold for a range of organophosphorus compounds. The kinetics of inhibition of acetylcholinesterase were consistent with the results of electrophoresis, i.e. they corresponded to those of a single enzyme in the presence of Triton X-100, but a mixture of enzymes in its absence. The susceptibility of the more sensitive components in these mixtures was determined.

Distribution of Species of Potato Cyst-Nematodes in South America

Abstract: Twenty six populations of potato cyst-nematodes from Colombia, Ecuador, Peru and Bolivia were examined and identified as Heterodera rostochiensis Woll. or H. pallida Stone. North of 15.6°S only H. pallida was found, but south of this latitude most populations examined were H. rostochiensis or a mixture of the two species. Possible reasons for the distribution of the two species being dependent on latitude are discussed, particularly the influence of daylength.

The purification and properties of glutamine-dependent asparagine synthetase isolated from Lupinus albus

Abstract: Glutamine-dependent asparagine synthetase, which transfers the amide nitrogen of glutamine to aspartate has been purified from Lupinus albus. The enzyme has a very high affinity for glutamine although it is able to use ammonia as a substrate. The enzyme is inhibited by $\alpha $-oxo acids, in particular $\alpha $-oxoglutarate; the possible physiological role is discussed. The activities of various other enzymes involved in ammonia assimilation have been measured during development of the cotyledon. A pathway of the route of ammonia entry into various amino acids has been proposed. The substrate specificity of the enzyme has been investigated with analogues of glutamine, aspartate and asparagine.

Insecticidal activity of the pyrethrins and related compounds. VII. Insecticidal dihalovinyl analogues of cis and trans chrysanthemates

Abstract: Eighteen esters of resolved cis- and trans-3-(2,2-difluoro, -dichloro or -dibromovinyl)-2,2-dimethylcyclopropanecarboxylic acids with 5-benzyl-3-furylmethyl, 3-phenoxybenzyl and α-cyano-3-phenoxybenzyl alcohols were prepared and evaluated for insecticidal activity against Musca domestica L. and Phaedon cochleariae Fab. Chlorine and bromine substituted esters are more active, in general, than those with fluorine, and in the most active esters, the cis isomer is more effective than the trans.

A generalized form of Fisher's logarithmic series

Abstract: SUMMARY A generalized form of Fisher's logarithmic series, based on the beta distribution of the second kind, is proposed for fitting species abundance data with exceptionally long tails. It is shown to give a better overall fit to light trap data than the log normal model. When Fisher was shown the species abundance data for C. B. Williams's catches of moths in light traps, and A. S. Corbet's tropical butterfly collections (Fisher, Corbet & Williams, 1943) it was natural that he should first consider describing the sample frequencies by a negative binomial distribution, since this distribution had been used successfully in describing spatial aggregation for single species. The negative binomial can be derived from the assumption that the population to be sampled consists of T species whose effective abundances, adjusted for differences in catchability, follow a gamma distribution akxk-le-ax

The use of weather data and counts of aphids in the field to predict the incidence of yellowing viruses of sugar-beet crops in England in relation to the use of insecticides

Abstract: SUMMARY Partial regression equations were calculated that relate the mean percentage of plants infected with yellowing viruses (beet yellows and beet mild yellowing viruses) in sugar-beet crops at the end of August to the number of days during January, February and March when temperatures fell below – 0.3 °C (31-5 °F) and the mean temperatures in April, for the 21 yr, 1951–71, using weather records from Rothamsted Experimental Station. Regression analyses were also made to find the effect of other factors including mean and minimum temperatures for the same months, and also mean counts of ‘green aphids’, mainly of the vector Myzus persicae, on sugar-beet plants during May and June. Significant relationships were established with all factors, but ‘frost-days’ and April mean temperatures accounted for the greatest percentage of the variance in yellows incidence. The calculations were made separately for the years from 1951 to 1958, when no routine advice was given to farmers about aphid control, and 1959–71 when a ‘spray-warning scheme’ was in operation, and many crops were sprayed at critical times to prevent aphid- and virus-spread. Weather factors had the same effects in both periods, but for any particular weather less virus was spread in the second period than in the first, although there were sufficient aphids, i.e. the numbers expected from the prevailing weather conditions. There was no evidence that insecticide treatment used in any one year affected aphid-incidence in subsequent years. Regression analyses on weather variables were also calculated separately for each of seventeen beet-sugar factory collection-areas, using weather records from local weather stations, and also the Rothamsted weather records. Unexpectedly, the fit of the regressions was always better with Rothamsted weather data than with local weather records. Mean yellows-incidence for the different factory areas declined from south to north, and there was a linear relationship with the square root of the latitude above 50 °C. At the same time the correlation coefficients relating yellows-incidence to ‘frost-days’ became smaller and less significant, and those showing dependence

Effects of direct drilling on the soil fauna

Abstract: Numbers of most species of invertebrates were greater in the soil in which direct-drilled crops were grown. Attacks by slugs and wireworms were much less serious after ploughing. Attack by stem-bor...

Factors that affect the persistence of pesticides in plants and soils

Abstract: Some of the factors that influence the persistence of pesticides are common to both plants and soils. These are, firstly, the characteristics of the pesticide, including its over-all stability either as parent compound or metabolites, its volatility, solubility, formulation, and the method and site of application. A second group includes the environmental factors, particularly temperature, precipitation (and humidity) and air movement (wind). The other factors depend on the properties of the plant or soil. Characteristics influencing the persistence of pesticides in plants include the plant species involved, the nature of the harvested crop, the structure of the cuticle, the stage and rate of growth and the general condition of the plant. Corresponding soil characteristics are the soil type and structure, its organic matter content, clay content, acidity or alkalinity, mineral ion content and degree of aggregation and its microbial population. Of these factors, the most important seem to be related to the chemical stability and physical characteristics of the pesticide; its stability exerting the greatest influence, otherwise volatility being more important in soil and solubility in plants. Of the plant characteristics, the species and rate of growth seem most important, and in soil, adsorption on to organic matter or clay minerals, and the populations of soil microorganisms present exert the greatest influence.

The behaviour of the nitrification inhibitor “n-serve” in broadcast and incorporated applications to soil

Abstract: N-Serve rapidly evaporated from coated fertiliser crystals scattered on glass plates or on soil. In the field in May more than 80% of N-Serve in a broadcast application volatilised overnight and no inhibition of nitrification was observed. Vapour loss from coated fertiliser incorporated 3 cm deep in soil was negligible and nitrification was inhibited for at least 9 weeks. The half-life of N-Serve was 28 days in a soil low in organic matter and 50 days in a soil high in organic matter. Movement of ammonium nitrogen and N-Serve over short distances in soil was observed but leaching of N-Serve more than 2 cm below the depth of incorporation was slight. Much N-Serve was lost whilst coating fertiliser, particularly when using a rotary evaporator. Analysis of treated fertiliser for N-Serve is necessary for reliable estimates of inhibitor concentration.

Effects of Potato Cyst-Nematodes On Potato Plants

Abstract: Observations of potato plant growth were made in plots containing a wide range of potato cyst-nematode populations following the use of resistant or susceptible varieties combined with fumigation treatments. Potato plants infested with many potato cyst-nematodes grew more slowly, were dwarfed, had smaller leaves and senesced earlier than plants with few nematodes but growth of Maris Piper, a variety resistant to Heterodera rostochiensis Woll. (pathotype A), was less affected than that of a susceptible variety, Pentland Dell. Throughout their growth nematode-infested plants contained less potassium in their foliage than uninfested plants and they were probably less efficient at taking up potassium. Although feeding nematodes probably abstracted a significant amount of nitrogen from heavily-attacked plants, the percentage of nitrogen in the haulm dry matter was little affected and did not seem to be a major factor limiting growth. There was no indication that photosynthetic capacity per unit area was lessened in the leaves of plants with root systems infested by many nematodes. Final yields were decreased by nematodes because infested plants were smaller and because they senesced earlier than plants infested with few nematodes.