Showing papers by "University of Hertfordshire published in 1972"

Plant growth substances produced by micro‐organisms of soil and rhizosphere

Abstract: Summary: Micro-organisms isolated from rhizospheres and rhizoplanes of wheat plants, and from root-free soil, produced growth regulating substances with the properties of gibberellins and indolyl-3-acetic acid (IAA). Substances inhibiting extensions of pea plant internodes and lettuce hypocotyls were also produced, especially by bacteria from the root region of seedlings 6 days old. Bacteria producing growth promoting substances were most abundant on roots of older plants. Seedlings grown aseptically with added gibberellic acid (GA3) and IAA, or grown with a soil inoculum, developed similarly and differed in their morphology from those grown aseptically without additives.

Plant growth responses to vesicular-arbuscular mycorrhiza iii. increased uptake of labile p from soil

Abstract: Summary Onion plants were grown in a range of soils labeled with 32P. It was found that although the mycorrhizal plants had taken up more phosphorus and grown larger, the proportion of 32P to total P (specific activity) taken up by mycorrhizal and non-mycorrhizal plants after 10 weeks was not significantly different. It is concluded that the mycorrhizal roots used the same source of labile phosphate but explored a greater volume of soil beyond the zone of phosphate depletion near the root surface. There was no indication that mycorrhizal roots had access to sources of phosphate different from those accessible to non-mycorrhizal roots. The specific activity of NaHCO3-extractable phosphorus differed considerably between the eight soils but the specific activity of absorbed phosphorus in the plants always corresponded closely to that of the soil in which they had grown.

Nitrogen-containing products from the thermal decomposition of flexible polyurethane foams

Abstract: The thermal decomposition of a polyester and a polyether flexible foam in a nitrogen atmosphere has been studied by gas chromatography, mass spec-trometry and elemental ultramicroanalysis. It is shown that the decomposition behaviours of the two foams are similar. At low temperatures (200 to 300 °C) there is a rapid and complete loss of the tolylene diisocyanate unit of each foam as a volatile yellow smoke leaving a polyol residue. The smoke has been isolated as a yellow solid (common to both foams) which contains virtually all of the nitrogen of the original foams and, under the conditions of test, is stable at temperatures up to 750 °C. Nitrogen-containing products of low molecular weight (mainly hydrogen cyanide, acetonitrile, acrylonitrile, pyridine and benzonitrile) observed during the high temperature decomposition (over 800 °C) of the foams are shown to be derived from the yellow smokes. At 1000 °C, approximately 70% of the available nitrogen has been recovered as hydrogen cyanide.

Effects of different Endogone strains on the growth of Paspalum notatum

Abstract: IN soils containing little available phosphate mycorrhizal plants often grow much better than non-mycorrhizal ones because they can absorb more phosphate from the soil1–4. In many tropical soils, such as the “campos cerrados” soils covering large areas of Brazil, shortage of available phosphate is a main factor limiting plant growth and there is no response to nitrogen until the phosphate deficiency is relieved5. In such soils inoculation with a mycorrhizal fungus may be beneficial, even though most soils naturally contain some fungi that form vesicular-arbuscular (VA) mycorrhiza. The indigenous mycorrhizal fungi can be killed by irradiation and VA mycorrhiza can then be re-established by inoculation with species of Endogone. Several different strains exist and effects of four strains on the growth of the tropical grass Paspalum notatum var. Batatai were compared in two Brazilian soils.

Ion permeability of phospholipid bilayers.

Abstract: PHOSPHOLIPID bilayers are an important part of biological membranes1,2 and consequently their physicochemical properties have been the subject of intense investigation. There has been much discussion about how similar the properties of phospholipid bilayers are to those of membranes3–5. Because of the importance of ion transport across membranes (such as in action potentials), the question of the similarities of the intrinsic ion permeability and conductance has been raised. However, reliable information on these properties of the unmodified bilayer is scarce and the situation is confused. Here we present, for the first time, accurate sodium and chloride ion permeability measurements across both charged and uncharged unmodified phospholipid bilayers.

Small‐angle X‐ray scattering of human serum high‐density lipoproteins

Abstract: Small-angle x-ray scattering (SAXRS) studies of the human serum high-density lipoprotein HDL2 indicate a symmetrical particle with a radius of gyration Rg = 46 A. The positions and intensities of subsidiary maxima in the scattering curves are not consistent with those of a uniformly electron dense sphere. Scattering curves calculated for spheres with a step-model radial electron density distribution, show good agreement with the experimental scattering curve for HDL2 only for specific values of the step function used. The dimensions obtained for the electron-deficient core and electron-rich shell model are quantitatively consistent with a predominantly surface location for the HDL2 protein and phospholipid head groups, the more hydrocarbon species being located in the interior of the particle.

Suspended solids and fisheries.

Abstract: The effect of suspended solids on freshwater fish is illustrated from field and laboratory studies on china-clay wastes together with work on the effects of other chemically inert material, wood fibre, ferric hydroxide, and oxidizable organic solids, and mention is made of work in the marine environment. Tentative water quality criteria formulated by the European Inland Fisheries Advisory Commission for inert suspended solids and inland fisheries are outlined and compared with conditions prevailing in rivers in the United Kingdom. Reference is made to current work by the Water Pollution Research Laboratory on the role of organic suspended matter in the presence of soluble poisons and on the effect of hydraulic conditions on the settlement and oxidizability of suspended solids from sewage effluent.

Radiosensitization of hypoxic cells in vitro: a water-soluble derivative of paranitroacetophenone.

Abstract: IT is believed that, in radiotherapy, the local control of some tumours is limited by radioresistant hypoxic regions in the tumour. Drugs which will sensitize these hypoxic tumour cells to radiation without increasing damage to surrounding well-oxygenated normal tissue, have, therefore, been demanded.

On the Genus Helicotylenchus Steiner, 1945 (Nematoda: Tylenchida), With Descriptions of Nine New Species

Abstract: The genus Helicotylenchus is discussed and a key to its species given. New species described are H. dihysteroides from tomato soil in Portugal, H. abunaamai from soil around roots of Citrus paradisi, Psidium guajava, Vitis vinifera and Gossypium hirsutum in Sudan; H. conicephalus from soil around roots of Aeolanthus myrianthus in Malawi and Citrus paradisi and Vitis vinifera in Sudan; H. densibullatus and H. talonus from soil around roots of A. myrianthus in Malawi; H. paraplatyurus from cultivated soil in Portugal; H. australis from soil around roots of Nicotiana tabacum in Western Australia; H. orthosomaticus from lucerne soil in Tanzania and H. willmottae from potato soil in India. H. microlobus is considered a valid species. Helicotylenchus annobonensis (Gadea, 1960) comb. n. is proposed for Tylenchorhynchus africanus v. annobonensis of Gadea, 1960.

Laboratory studies on the life-histories of four enchytraeid worms (Oligochaeta) which inhabit sewage percolating filters

Abstract: SUMMARY The life-histories of four enchytraeid worms, Lumbricillus rivalis, Enchy-traeus coronatus, E. buchholzi, and E. albidus which occur in sewage percolating filters, were studied under laboratory conditions at 8, 15 and 20°C. The number of ova per cocoon varied from 0 to 50 (L. rivalis), 0 to 33 (E. coronatus), 1 to 9 (E. buchholzi) and 0 to 22 (E. albidus). The mean number of ova per cocoon was highest at 15°C for all species except E. coronatus which had a highest mean value at 8°C. The number of ova in cocoons was correlated with cocoon length (P < 0.001) for all species. Cocoon production usually increased with temperature ranging from 0.8 cocoons per adult per week at 8°C to 2.0 at 20°C for L. rivalis, and from 1–4 to about 2.6 for E. coronatus and E. buchholzi. The total number of ova produced by each E. coronatus (350 at 8°C to 550 at 20°C) was similar to that produced by each L. rivalis (600 at 8°C to 350 at 20°C) and was about five times greater than the total numbers produced by the other two species. Cocoon and ova production and the number of ova per cocoon varied with the age of the adult, usually reaching a peak soon after maturity. Hatching success was low and generally 40–50 % of ova failed to develop; subsequent mortality among immature worms was about 10–20%. Growth was more rapid at the higher temperatures; L. rivalis matured in about 26 days at 20°C, the clitellum forming when the worm was 13–14 mm long; data for the other species are 13 days and 5–6 mm (E. coronatus); 16 days and 3–4 mm (E. buchholzi); 28 days and 13–14 mm (E. albidus). The maturation period at 8°C was at least twice that at 20°C. The generation period (cocoon to cocoon) was about a month at 20°C for all species except E. albidus (2 months), but as some species had longer reproductive periods than others the actual number of generations per year was highest in E. buchholzi, 7.0 per year, and lowest in E. albidus, about 3.3 per year, At 8°C all four species had between 1.4 and 2.8 generations a year. A comparison of expected and observed population densities of L. rivalis and E. coronatus in a sewage percolating filter showed that neither achieved values approaching their potential summer densities although ample food was apparently available. Of the four species studied only E. buchholzi produced viable ova without pairing.

Quasi Newton techniques generate identical points II: The proofs of four new theorems

Abstract: This report contains the proofs of four new theorems relating to the behaviour of Broyden's [1] family of variable metric formula for solving unconstrained minimisation problems. In particular, it is shown that if the linear search at each iteration is perfect, then the sequence of points that is generated is independent of the member of the family used at each iteration, provided the matrix remains nonsingular. This result extends Powell's [14] proof of convergence for the original formula on any convex function to all members of the family.

Hereditary factor-VII deficiency in the beagle.

Abstract: Summary. Hereditary factor-VII deficiency is identified in another large colony of beagles. Evidence is presented to suggest that this trait may be relatively widespread in colonies in Great Britain.

Cereal aphids, their parasites and predators caught in cages over oat and winter wheat crops

Abstract: SUMMARY The trapping of alate aphids in emergence cages each 1 yd2 (0–83 m2) over cereal crops from mid-June to the end of July, 1964 to 1971, always revealed colonies of cereal aphids within the crop. Four species, Sitobion avenae, S. fragariae, Metopolophium dirhodum and Rhopalosiphum padi occurred every year in different proportions. Alate aphids from winter wheat were most numerous in 1968 and fewest in 1967. Alatae developed slightly earlier in cages than in the field and peak catches were a few days earlier than in a nearby 12-2 m suction trap. Cereal aphid colonies were adversely affected by bad weather in May, e.g. in 1969, and by predators. Coccinellidae (chiefly Propylea 14-punctata) were the dominant predators in 1971 and 1968, Syrphidae in 1966, 1971 and 1968 and Chrysopidae in 1970. Parasites belonging mainly to the genus Aphidius were numerous every year. When hyperparasites such as Asaphes vulgaris, Lygocerus sp., Conostigmus sp. and Phaenoglyphis sp. were abundant as in 1967, they affected numbers of aphids in the current year and increased them in the following year (1968), possibly by hindering early, heavy parasitism. Hyperparasites could have an important influence in fluctuations of cereal aphid populations from year to year. Aphids of one species or another are always present in cereal crops in sufficient numbers during the summer months to provide copious quantities of honey dew, and this is unlikely to be a limiting factor in the biology of the wheat bulb fly, Leptohylemyia coarctata.

Effects of defoliating different zones on the plant in field beans ( Vicia faba L.)

Abstract: SUMMARY The mean yield of grain of untreated spring field beans was 2750 kg/ha. By the use of differential defoliation, upper and lower limits were set for the photosynthetic contributions of four zones to this yield: (i) stems and pods 0–300 kg; (ii) leaves below first flowering node 280–1150 kg; (iii) leaves on first nine flowering nodes 720–2100 kg; (iv) leaves above first nine flowering nodes 260–1150 kg. The evidence suggested that all zones functioned below their full photosynthetic efficiency when other zones were present and that competition between zones for sites to store carbohydrate was a greater limiting factor than mutual shading.

Vehicle steering means

Abstract: Steering apparatus for causing a wheeled vehicle automatically to follow a roadway or prepared track comprises a follower on the vehicle mounted on the forward end of a pivoted lever so as to be movable laterally to and fro to trace the line of a stationary longitudinal guidance element lying along the length of the track. The lever carrying the follower, which lever projects forwardly of the axle of the steerable wheels, has its rear part resiliently coupled to the track rod of a self-centering steering mechanism for the wheels.

Infection of Protoplasts from Yeast with Tobacco Mosaic Virus

Abstract: PROTOPLASTS from higher plant cells can become infected with plant viruses under special conditions1–3, and it has been shown that yeast cells can become infected with viruses normally found in different fungal genera4. We thought that naked yeast cells (yeast protoplasts) might provide a suitable system for demonstrating the infection of yeast cells with a virus such as tobacco mosaic virus (TMV). We report here how we infected yeast protoplasts with TMV and measured its multiplication in them.

Dynamic Debugging in BASIC

Abstract: One of the main advantages that on-line working provides is the ability to interact with a running program. Interaction at run-time is important from two standpoints. Firstly, it enables the programmer to control the action of the program by providing suitable data as the execution progresses. Secondly, and most importantly, given the right facilities, it enables a programmer dynamically to debug the program. One of the most popular languages designed explicitly for on-line working is BASIC. Although one is able to interact in the first sense, most implementations fail to give any run-time debugging facilities to the BASIC user. This paper describes the range of run-time debugging facilities provided on an implementation of BASIC at Hatfield Polytechnic on an ICL 803.

Gastric impaction in a pony: relief via laparotomy.

Abstract: UMMARY A case of gastric impaction in an 11 year old pony which was successfully treated by a gastrotomy is described. RESUME On rapporte un cas de surcharge gastrique chez un poney de 11 ans gueri par gastrotomie. ZUSAMMENFASSUNG Der Artikel beschreibt einen Fall von Magenuberladung bei einem Pony, der erfolgreich durch Gastrotomie behandelt wurde.

Biological Sciences: Crystal Structure of a Novel Curariform Agent

Abstract: THE belief that optimal competitive neuromuscular blockade occurs with compounds having two quaternary centres 12.5 A apart1,2 has been progressively weakened by the demonstration3 that (+)-tubocurarine is a monoquaternary compound, by the X-ray studies4 on a potent curarizing steroidal derivative* in which the interjacence is 11.1 A and by the even closer centres (9.7 A) in the similarly active diallyl bis-nortoxiferine. Further evidence that an interquaternary distance of 12.5 A is not critical in competitive neuromuscular blocking drugs is provided by the novel 1,1′-azobis-arylimidazo[1,2-a]pyridinium bromides, in which this interjacence is close to 7.5 A.

Flight activity of Plusia gamma in the laboratory

Abstract: Aktograph experiments showed lowered light thresholds for flight during the first three days after emergence of adult moths. Maximum flight duration was also reached at the third day. These three days probably represent the time when migration would occur in wild insects. Migration of insects usually begins post tenerally so it should be possible to direct migratory behaviour (i.e. the tendency for continued flight) in young adults of each generation of a species that migrates. The flight behaviour of Plusia gamma L. was studied in the laboratory to test this possibility. Resume ACTIVITE DE VOL DE PLUSIA GAMMA AU LABORATOIRE Des experiences utilisant un actographe ont montre une inhibition moins forte de la lumiere sur le vol pendant les trois premiers jours suivant leur emergence. La duree maximum de vol est atteinte au 3eme jour. Il est suggere que ces premiers trois jours de la vie imaginale pendant lesquels le papillon a tendance a voler de facon continue, correspondent a la periode d'activiTE migratoire.

Image analysis system

Abstract: An image analysis system in which the conventional monochrome television monitor is replaced by a colour television monitor. The video signal relating to the field under analysis is arranged to produce a monochrome display in the colour monitor but signals obtained from processing the video signal are arranged to produce distinctive colours in the monochrome display. Circuits are described by which the detected signal pulses obtained by threshold detection of the video signal, detected signal pulses of amended duration (both increased and decreased duration), count pulses and shape classifying pulses may be arranged to produce different colours in the display. Where alpha-numeric characters are included in the television display to indicate a numerical value of e.g. the number of features detected and counted, circuits are described for producing the alpha-numeric characters in the same colour as the parameter to which they relate, is displayed.