Showing papers by "University of Hertfordshire published in 1984"

A hypothesis relating critical potassium concentrations for growth to the distribution and functions of this ion in the plant cell

Abstract: Summary The growth and metabolism of plants in response to different concentrations of tissue K is discussed in relation to current knowledge about the distribution and functions of this ion in plant cells. In the cytoplasm, K has an important role in providing the correct ionic environment for metabolic processes. The ionic requirements of protein synthesis seem to be particularly important in determining the composition of the cytoplasm. Potassium is not replaceable in its cytoplasmic functions and the plant probably needs to maintain the cytoplasmic concentration of K in the range of 100 to 200 mM. Potassium salts in the vacuole are involved in the generation of turgor but when unavailable they can be replaced by other solutes. Salts of other cations such as Na and Mg are often a readily available alternative to K but in their absence organic solutes must be accumulated. With these observations as a basis, a model is proposed in which, as the concentration of K in the tissue declines, the concentration in the cytoplasm is initially maintained constant, while that in the vacuole decreases. In order to maintain turgor, alternative solutes are accumulated in the vacuole as replacements for K. It is assumed that K in the vacuole can only drop to a certain minimum level and, once this is reached, any further decline of tissue K must be at the expense of that in the cytoplasm. This leads to a decrease in the rate of metabolic processes that depend on K and so to a decline in growth. The hypothesis explains the observed relationships between growth and concentrations of K in tissues, and their modification by Na and other cations.

The growth and activity of winter wheat roots in the field: the effect of sowing date and soil type on root growth of high-yielding crops

Abstract: The effect of sowing date on root growth of high-yielding crops (8–1 It grain/ha, 85% D.M.) of winter wheat (Triticum aestivum L. cv. Hustler) was measured at Rothamsted and Woburn in 1980 and 1981. Roots were sampled by coring on five occasions and changes in root dry weight and length were determined. The average growth rate between March and June was about 1 g/m2/day (200 m/m2/day), over 5 times that measured between December and March. Increases in root weight or length with time were generally exponential to anthesis when the crops had 101–172 g root/m2 (20–32 km/m2). September-sown wheat had more root than October-sown wheat at all times, but whereas early differences in length were maintained throughout the season, root weights converged between March and June. Overall, there was no significant difference in root dry-matter production between sites at anthesis, but there was a substantial difference between years. Differences in root growth between crops were reduced by plotting the amount of root against either the number of days from sowing or accumulated thermal time. Using che latter, root growth between December and June was reasonably linear although there was some indication of a lag below 500 °C days. Regression equations obtained for the relationships between root growth and accumulated thermal time also fitted previously published data and may provide general descriptions of root growth with time.Roots of September-sown crops reached 1 m depth by December but those of October-sown crops were not detectable at this depth until April. For most crops the distribution of roots with depth was reasonably described by an exponential decay function, with over 50% of the roots in the top 20 cm of soil at all times. At Woburn in 1981, a plough-pan restricted roots to the upper soil horizons for most of the season but apparently had little effect on the total amount of root produced. For one of the experimental crops an empirical mathematical function describing the distribution of roots with depth and time is presented.Using the data from this and previously published studies, the relationship between grain yield and the amount of root at anthesis was investigated. Total root length was positively correlated with grain yield but nonetheless similarly yielding crops could have different-sized root systems. Total root dry weight was poorly correlated with grain yield.

Cobalt-nickel separation by solvent extraction with bis(2,4,4 trimethylpentyl)phosphinic acid

Abstract: The use of an organophosphinic acid to separate cobalt from nickel by solvent extraction is described. Comparative data indicate that the phosphinic acid is superior to analagous phosphoric and phosphonic acids in terms of cobalt-nickel selectivity and the ability to reject calcium. Important reagent properties, such as low aqueous solubility and hydrolytic stability, are discussed. The results of continuous, counter-current, mini-plant tests demonstrate the recovery of high purity cobalt from concentrated nickel sulphate solutions.

Crystal structures of clay minerals and related phyllosilicates

Abstract: The paper reviews the structures and crystal chemistry of clay minerals, including interstratified minerals and related phyllosilicates. Brief accounts are presented of the disordered structures encountered in the different mineral groups and a conceptual structural model for interstratified minerals is outlined.

The effects of morphology on 1H NMR spectra and relaxation in semicrystalline polyolefins

Abstract: Bref resume du role de l'heterogeneite structurale, des couplages magnetiques dipolaires, de la structure moleculaire et du mouvement moleculaire dans la determination des spectres RMN du proton et des proprietes de relaxation de solides heterogenes tels que les polymeres semicristallins. Mesures de la relaxation spin-reseau du proton en labo et en referentiel tournant pour du polyethylene cristallise en solution et au fondu, du polypropene isotactique recuit et trempe et du polybutene-1 isotactique

Metal concentrations in sludges and soil from a long-term field trial

Abstract: Metal contents are reported of the soils from a field experiment in which two rates of various organic manures, including sewage sludge and sludge compost, were applied from 1942 to 1961. Changes in the concentrations of some elements in the sludges during the 20 years are also presented.The percentage recoveries of the added metals Zn, Cu, Ni, Pb, Cd and Cr in the topsoil varied from 71 to 96%. In 1960, extractability of the metals from the soils by 0·05 M-EDTA was 50% of the aqua regia-soluble total metals. This figure did not vary greatly with metal or with the type of organic manure that was applied.

The Structural and Evolutionary Relationships of the Prolamin Storage Proteins of Barley, Rye and Wheat

Abstract: The major endosperm storage proteins of barley, wheat and rye are soluble in aqueous alcohols, either native or after the reduction of disulphide bonds, and can be defined as prolamins. They can be divided into three groups on the basis of their chemical characteristics, notably their molecular mass and amino acid composition, and the chromosomal location of their structural genes. Two of the groups, the high molecular mass prolamins and the sulphur-poor ( $\omega$ -gliadin-type) prolamins, show clear homology between the three species. The remaining prolamins are characterized by a high content of cysteine. In wheat this is a complex mixture of at least three groups of components that vary in their aggregation properties and N-terminal amino acid sequences. The precise chemical and genetic relationships of those components to each other and to the more clearly defined groups of sulphur-rich prolamins of rye and barley are still not completely understood.

The growth and activity of winter wheat roots in the field: root growth of high-yielding crops in relation to shoot growth.

Abstract: Root growth is considered in relation to shoot growth for high-yielding crops of winter wheat grown on three soil types in 1980 and 1981. From the time that nitrogen was applied to anthesis, shoot growth was rapid and effectively linear in relation to thermal time, whereas root growth entered a rapid linear phase after about 500–600 °C days, well before the application of nitrogen. Between double ridges and anthesis, shoots accumulated dry matter 10 times faster than roots on average. The relationship between root and shoot growth was different in the two years, which was probably due to reduced assimilate production in 1981 as a result of the dull, cloudy weather. At anthesis, average root: plant ratios for 1980 and 1981 were 0·132 and 0·093 respectively but no significant differences were caused by sowing dates or sites, despite the presence of a plough-pan on one of the soils.Root:plant ratios declined from about 0·4 in winter and early spring to about 0·1 by anthesis. There was considerable variability in root:plant ratios for different crops during winter and early spring, caused in part by differences in soil-N availability and timing of application of fertilizer nitrogen.

Blind rivet assembly

Abstract: A blind, self-plugging rivet assembly for securing together two members (42, 43) is of the type comprising a tubular shell (13) with an enlarged head (14) at one end, and a stem (12) which extends through the bore (15) of the shell, the stem having an enlarged head (38) beyond the tail end (18) of the shell The shell has a weakened zone (19) formed by three slits (22) extending along part of the shell shank and spaced apart equiangularly around it The stem head (38) lies beyond the shell tail end, and has an underhead surface (39) which is slightly convex and is bounded by a sharp edge (40) The stem has a pulling portion (32) connected by a breakneck to a plugging portion (31) which is an interference fit in the shell bore Adjacent the breakneck the plugging portion has a cylindrical skirt which, when the rivet has been installed, can be deformed outwardly to lock the plugging portion to the shell A bead on the stem guides the tool for deforming the skirt

Regulation of spore germination of the vesicular-arbuscular mycorrhizal fungus Acaulospora laevis by soil pH

Abstract: Resting spores of the vesicular-arbuscular mycorrhizal fungus Acaulospora laevis germinated poorly (less than 12%) on water agar under axenic conditions. In soil their germination was regulated by pH, being optimum at pH 4–5 and declining to less than 10% in neutral or alkaline conditions.

A Comparison of Methods for Measuring Turgor Pressures and Osmotic Pressures of Cells of Red Beet Storage Tissue

Abstract: Two methods for measuring the turgor pressures of cells in discs of storage tissue of red beet (Beta vulgaris L.) were compared, and a centrifugation method for extracting sap from frozen and thawed tissue was evaluated. Turgor pressures were measured directly using a pressure probe, or indirectly using a vapour pressure osmometer. With the latter, discs were placed directly in the osmometer chamber and turgor was calculated as the difference in osmotic pressure before and after freezing and thawing. Turgor in freshly cut discs, measured with the pressure probe, was between 0 012 MPa and 0-118 MPa with a mean ±s.d. of 0 092 + 0-032 MPa (n = 24). That measured with the osmometer varied between 0-08 MPa and 0-12 MPa with a mean ±s.d. of 0-09 ±0-10 MPa(n = 54). After vacuum infiltration of discs with distilled water, the turgor measured with the pressure probe increased to 1-05 1-12 MPa. Turgor measured with the osmometer also increased after vacuum infiltration but was, on average, 12% lower than that measured with the pressure probe. Overall, the results suggest that for routine measurements, the osmometer can provide reasonable estimates of the turgor of cells in beet discs. This is because a number of factors that, potentially, could interfere with this method have only a small effect in this tissue. None of the measured turgors is indicative of that occurring in intact storage roots because both excision and vacuum infiltration of discs alter the concentrations of solutes in the extracellular space. The osmotic pressure of sap extracted by centrifugation from frozen and thawed discs was not significantly different from that measured by placing frozen and thawed discs directly in the osmometer. Solute concentrations in the sap were not significantly different from those measured by chemical extraction of discs.

Sampling conditions for reliable routine detection by enzyme-linked immunosorbent assay of three ilarviruses in fruit trees.

Abstract: SUMMARY Enzyme-linked immunosorbent assay (ELISA) was used to test plum trees for prune dwarf (PDV), Prunus necrotic ringspot (NRSV) and apple mosaic (ApMV) viruses, cherry trees for PDV and NRSV, and apple trees for ApMV. Optimum conditions were determined for sampling in large-scale surveys for these viruses. All three viruses were detected throughout the growing season in individual samples of young leaves, or twigs with newly formed buds. However, when single infected leaves were combined with different numbers of healthy leaves, tests were most successful for all three viruses early in the growing season. PDV was detected in 1/40 (infected/total leaves) cherry leaves in April and May and 1/40 plum leaves until July, whereas NRSV was detected in 1/20 cherry leaves until July and 1/20 plum leaves until May. ApMV was detected in 1/20 apple or plum leaves until June but was detected less readily in mature leaves after June than either NRSV or PDV. There was no evidence of uneven distribution of virus infection in the trees. The viruses were detected in leaf samples kept for 8 wk at 3°C but freezing was less reliable for storage especially with ApMV. ApMV was detected in tests on plants held for several weeks at 25°C, and PDV and NRSV in plants held at 30°C.

Specific weight and wheat quality

Abstract: UK winter and spring wheats were studied to establish correlations between specific weight and flour yield. In general, correlations were poor and could not be used for predicting flour yield from specific weight. Specific weight/flour yield relationships are influenced by year, growing site, variety and endosperm texture. The moisture content and moisture history of wheat influences its specific weight, and no universal factor can be applied to correct specific weight results to a fixed moisture basis. Individual wheats exhibit their own correction factors and these are different for wheats that have been dried or damped. 1000 kernel weight was not found to be a suitable alternative to specific weight for flour yield prediction.

Radiosensitization of mammalian cells by transition metal complexes containing nitroimidazole ligands

Abstract: Various transition metal complexes containing nitroimidazoles as ligands have been shown to act as radiosensitizers of hypoxic cells in vitro. Sensitization by cis-Pt(II)Cl2 (nitroimidazole)2 complexes is no greater than that which can be demonstrated by the free nitroimidazole ligand alone. These results differ from those previously described for the compound FLAP where an ER of 2.4 was obtained at a concentration of 50 microM. We report that, even using the same treatment technique, the maximum ER that can be achieved is 1.2. Further, the sensitizing efficiency of FLAP cannot be improved when cells are kept in contact with the compound for 12 hours in air prior to deoxygenation and irradiation. In contrast, Rh(II) complexes show much greater sensitization than can be obtained with the free ligand and these compounds are in turn more efficient sensitizers than the comparable Pt(II) complexes.

Control of metal application rates from sewage sludge utilization in agriculture

Abstract: During the treatment of sewage, a sludge is produced, which must be disposed. For many treatment works, agricultural use of the sludge is the most cost‐effective disposal option. In using sludge as a fertilizer replacement or soil conditioner in agriculture, the environment must not be endangered. In this objective, toxic metal accumulation is of special interest because excessive concentrations in sludged soil can reduce crop yields or result in unacceptable accumulations of toxic metals in crops with consequent hazard to the food chain. Although sewage sludge contains certain quantities of metals from natural sources, there are significant amounts derived from industrial effluents discharged to sewers. The paper will review all of these aspects and will examine critically the various policies of controlling metal accumulation in sludged soil with particular reference to the soil quality criteria (maximum permissible concentrations) which have been adopted.

Barrier systems and the like

Abstract: A barrier or personnel guidance system is disclosed which utilizes vertical posts and horizontal rails each comprising an elongate central member formed, for example by a metal extrusion covered by cladding, formed for example by a plastics extrusion or extrusions, the central member and the cladding having complementary inter-engaging retaining formations. The central member comprises a central passage and lateral channels in which can be engaged various ancillary members whereby posts and rails can be interconnected, panels fitted, gate assemblies constructed and the like constructional facilities afforded.

Lourdes cures and their medical assessment.

Abstract: Historical background In 1858 a 14-year-old girl claimed that a lady had appeared to her at the cliff of Massabielle, just outside the town of Lourdes in the French Pyrenees. The child's reports of their conversations led to the conclusion that this lady was the Blessed Virgin Mary, mother of Jesus Christ, and Lourdes rapidly became a place of pilgrimage. Although the healing of the sick did not feature in the statements made by the lady-, sick people seeking a cure that could not be given to them by their doctors soon became prominent among the pilgrims: a few of them found what they sought. The local authorities, both Church and State, were suspicious and disapproving. After initially putting every obstacle in the way of the cult, the State eventually decided to leave the matter to the Church. The Bishop set up a commission to investigate the problem. Following their report 4 years later he declared that 'it is our verdict that the Immaculate Mary, Mother of God, did really appear to Bernadette Soubirous . . . Our conviction is based on the testimony of Bernadette but more especially on the events which have occurred and which have no explanation save in the intervention of God'. The Catholic Church is well used to claims of miraculous cure and to evaluating them by means of a set of criteria devised in 1735 by Cardinal Lambertini (afterwards Pope Benedict 14th). The rules are: (1) The disease must be serious, incurable or unlikely to respond to treatment. (2) The disease which disappeared must not have reached a stage at which it would have resolved by itself. (3) No medication should have been given, or if some medicines were prescribed then they must have had only unimportant effects. (It is most unusual nowadays to find a case completely untreated and this rule is interpreted as excluding any patient who has had potentially curative treatment unless that treatment can be demonstrated to have failed.) (4) The cure must be sudden and reached instantaneously. (This is now extended to; include cures developing over a period of days.) (5) The cure must be complete, not partial or incomplete.

Winter mortality, development and reproduction in a field population of Myzus persicae (Sulzer) (Hemiptera: Aphididae) in England

Abstract: Population change in Myzus persicae (Sulz) overwintering on spring cabbage in south-eastern England was studied in relation to meteorological and biological factors Leaf surface wetness and temperature were correlated significantly with rate of population change, but rainfall and wind were not Growth and development continued slowly throughout the winter, and the relationship with temperature is shown Hymenopterous parasites, the fungus Entomophthora and predatory spiders did not affect winter survival

Regulation of Aspartate Kinase Isoenzymes in Barley Mutants Resistant to Lysine plus Threonine Construction and Analysis of Combinations of the Lt1a, Lt1b, and Lt2 Mutant Genes

Abstract: Two homozygous mutant lines of barley ( Hordeum vulgare L.) R3202 ( Lt1b/Lt1b ) and R3004 ( Lt2/Lt2 ), are resistant to lysine plus threonine. They contain aspartate kinase isoenzymes with lost or decreased feedback sensitivity to lysine in either isoenzyme AKII (R3202) or isoenzyme AKIII (R3004). A homozygous double mutant line ( Lt1b/Lt1b, Lt2/Lt2 ) has now been constructed that grows vigorously on 8 millimolar lysine, 8 millimolar threonine, and 1 millimolar arginine. Both AKII and AKIII from the double mutant have altered lysine sensitivities, identical to those previously observed in R3202 and R3004, respectively. Aspartate kinase activity in extracts of leaves, roots, and the maturing endosperm of the double mutant was much less sensitive to lysine inhibition than the enzyme in comparable extracts of the parent cv Bomi, suggesting that aspartate kinase is expressed in a similar manner in different tissues of barley. A further mutant, R2501, resistant to lysine plus threonine has now given rise to a homozygous line ( Lt1a/Lt1a ), which had previously not been possible. AKII isolated from the homozygous line was completely insensitive to 10 millimolar lysine; however, the combined action of 10 millimolar lysine and 0.8 millimolar S -adenosylmethionine inhibited it by 60%, demonstrating the retention of some of the regulatory characteristics of the wild type enzyme.