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Showing papers by "University of Hertfordshire published in 1977"


Journal ArticleDOI
03 Feb 1977-Nature
TL;DR: A concept is developed for the regulation of populations by density-dependent movement, rather than by overt competition alone, which is seen as maximising the reproductive advantage of a balance between migratory and congregatory behaviours.
Abstract: A concept is developed for the regulation of populations by density-dependent movement, rather than by overt competition alone. Fitness is seen as maximising the reproductive advantage of a balance between migratory and congregatory behaviours. Population density is shown to be spatially, as well as temporally dynamic and a mechanism is proposed that accounts for observed spatial behaviour.

430 citations



Journal ArticleDOI
TL;DR: Recurrence risks of severe mental retardation in cases where it is possible to establish a definite diagnosis are discussed and the potential value, for genetic counseling purposes, of a categorizing such patients into broad symptomatological groups is suggested.
Abstract: An etiological survey is presented of all suveryl retarded children living in Hertfordshire, at home and in residential care, born between January 1, 1965, and December 31, 1967. One hundred and forty-six children (87 boys and 59 girls) were ascertained, out of a total population of 46,960, with a prevalence of 1 in 320 or 3.1 per 1,000. Approximately 1/3 (47) had the Down syndrome, 1 per 1,000 population. It was possible to establish a diagnosis in a further 45 cases, which included 1 additional case of autosomal chromosome abnormality and 7 each of autosomal dominant, recessive and X-linked conditions; 17 were associated with presumed multifactorial etiological factors; in 6 the condition was thought to have been caused by an environmental agent. It was not possible to establish a cause in the remaining 54 cases. Recurrence risks of severe mental retardation in cases where it is possible to establish a definite diagnosis are discussed and the potential value, for genetic counseling purposes, of a categorizing such patients into broad symptomatological groups, is suggested.

65 citations


Journal ArticleDOI
TL;DR: The relationships between rain and blight (Phytophthora infestans) were studied in unsprayed crops of cultivars differing widely in foliage and tuber susceptibility, finding that stem lesions can provide an important source of inoculum for tubers.
Abstract: SUMMARY The relationships between rain and blight (Phytophthora infestans) were studied in unsprayed crops of cultivars differing widely in foliage and tuber susceptibility. The occasions when tubers were infected depended on rain and not cultivar, but numbers of tubers infected after rain was affected by the blight susceptibility of the cultivar. Infected tubers were first found when less than 5 % (BMS key) of the potato foliage was infected but few fresh infections occurred when 50–75% of the foliage had been destroyed. Some tubers were infected after 8 mm rain (tubers near the surface with even less) but large increases in numbers of tubers infected usually occurred only after 25 mm or more had increased soil moisture to above ‘field capacity’ around the tuber for at least 24 h. The most susceptible cultivars Ulster Ensign and Arran Banner had all plants with some tuber blight, and some plants with all tubers affected and often many lesions per tuber. Cultivars of intermediate susceptibility, King Edward and Up-to-Date, had some plants without blighted tubers, many with a few and very few with all. The more resistant cultivars Majestic and Arran Viking had many plants without infected tubers and many lesions that aborted while still necrotic threads, so that the fungus did not spread. Most infections occurred through tuber eyes, lenticels or sometimes growth cracks. The distribution of blight lesions on tubers differed in the different seasons, for example, lenticels were most commonly infected on Arran Banner and Ulster Ensign and eyes on King Edward, Majestic and Arran Viking. In late or slowly developing attacks, lesions on stems became more numerous and larger than in fast, early attacks and were prolific sources of spores on King Edward and Up-to-Date but not on Majestic and Arran Viking. Because much rain water runs down the stems of Up-to-Date and King Edward, stem lesions can provide an important source of inoculum for tubers.

56 citations


Journal ArticleDOI
TL;DR: An assessment of the value of modern, high-performance liquid chromatography for this application has shown that mixtures of underivatised bile acids may be resolved by reversed-phase chromatography, which separates isomeric acids and those differing in the extent of hydroxyl substitution.

56 citations


Journal ArticleDOI
TL;DR: Evidence is presented which suggests that the yield increases were due to the suppression of aphids, plant-sucking bugs, stem-boring fly larvae, and perhaps nematodes.
Abstract: Ryegrass swards at fourteeo widely separated sites in England were assessed for yield, botanical composition and invertebrate populations, with and without insecticide treatment during a 4-year period. Treatment with insecticide reduced the numbers of almost all invertebrate groups sampled and increased grass growth at some time at all but one site. Annual DM output was increased by 0–32% depending upon the site concerned. Evidence is presented which suggests that the yield increases were due to the suppression of aphids, plant-sucking bugs, stem-boring fly larvae, and perhaps nematodes.

52 citations


Journal ArticleDOI
TL;DR: Autotrophic ammonia-oxidizing bacteria were detected in some Bangladesh and Sri Lanka tea soils and in three other Bangladesh soils and identified as species of Nitrosolobus, Nitrosomonas and a new species ofNitrosospira.
Abstract: Autotrophic ammonia-oxidizing bacteria were detected in some Bangladesh and Sri Lanka tea soils and in three other Bangladesh soils. Numbers ranged from 25 to 5500 organisms/g dry soil. Pure cultures were obtained from all the soils either by picking colonies from silica gel plates used for counts or by enrichment culture procedures. The isolates were identified as species of Nitrosolobus, Nitrosomonas and a new species of Nitrosospira.

49 citations


Journal ArticleDOI
TL;DR: SUMMARY Samples from 265–333 randomly selected crops of winter wheat in England and Wales were taken annually from 1970 to 1975 after heading, the main sample being at the milky-ripe growth stage, when yellow rust was most severe and brown rust was very prevalent.
Abstract: SUMMARY Samples from 265–333 randomly selected crops of winter wheat in England and Wales were taken annually from 1970 to 1975 after heading, the main sample being at the milky-ripe growth stage. The percentage of the area of the top two leaves affected by diseases was recorded and, in the last five years, samples were tested for infection by barley yellow dwarf virus: in 1975 stem base diseases were recorded. Scptoria was the most common and severe disease in four of the six years. In. 1970 mildew was most severe and, in 1975, brown rust. The severity of infection by Septoria tended to be greater in southern and western areas in wetter summers and in crops following a previous cereal. Yellow rust was most severe in 1972, when it was very prevalent on cv. Joss Cambier. In 1973 the disease was less severe, but in 1974 and 1975 the severities of both yellow and brown rusts increased in association with the popularity of susceptible cultivars. There was a tendency for yellow rust to be more severe on early-sown crops. In 1975, eyespot was recorded on 11·8 per cent of the stems. 1·8 per cent of the symptoms being severe. Fungicidal sprays were associated with a slightly smaller incidence of stem base diseases. Estimates of percentage loss in yield due to particular diseases vary from almost zero caused by yellow rust in 1970 to 7·4 per cent loss caused by Septoria in 1972.

48 citations


Journal ArticleDOI
TL;DR: The factors which create crop marks at two archaeological sites, at Glenlochar, Kirkcudbrightshire and at Fisherwick, Staffordshire, are examined in some detail as mentioned in this paper.

43 citations


Journal ArticleDOI
TL;DR: Even with the highest dose of 600 μg dry powder sal butamol no subjective or objective side-effects were observed and the inhalation of salbutamol in a lactose base was well tolerated by all the patients.
Abstract: 1 A double-blind placebo controlled comparison of the bronchodilator effects of salbutamol inhaled as a dry powder and by conventional pressurized aerosol was carried out in 20 patients with chronic bronchial asthma. 2 No significant difference in the bronchodilator response between 400 μg and 600 μg of dry powder and 200 μg from the aerosol was detected. 3 Even with the highest dose of 600 μg dry powder salbutamol no subjective or objective side-effects were observed and the inhalation of salbutamol in a lactose base was well tolerated by all the patients.

42 citations


Journal ArticleDOI
01 Apr 1977-Polymer
TL;DR: In this paper, the melting points and glass transition temperatures have been measured for a series of arylene ether sulphone homo-and co-polymers and it has been shown that structural changes in repeat unit structure cause marked changes in mechanical properties by altering the packing density of polymer repeat units rather than by changing chain polarity or rigidity.

Journal ArticleDOI
TL;DR: Of a range of structural lysine analogues tested at 10 mM, only S-2-aminoethyl-L-cysteine inhibited the l Lysine-sensitive activity completely, and the other aspartate-derived amino acids, homoserine, isoleucine and methionine, were without effect.

Journal ArticleDOI
TL;DR: Durrant et al. as discussed by the authors investigated the influence of sodium on the water status, growth, and physiology of leaves of soil-grown sugar beet subjected to a range of soil water potentials in controlled environments.
Abstract: The effects of sodium chloride on the water status, growth, and physiology of sugar beet subjected to a range of soil water potentials were studied under controlled conditions. Sodium chloride increased plant dry weight and the. area, thickness, and succulence of the leaves. It increased the water capacity of the plant, mainly the shoot, but there was no evidence that it altered the relationships between leaf relative water content and the leaf water, osmotic, and turgor potentials or changed the way stomatal conductance arid photosynthesis responded to decreasing leaf water potential. The greater leaf expansion in sodium-treated plants is thought to be the consequence of adjustments made by leaf cells to accommodate changes in ions and water in a way that minimizes change in water and turgor potentials. It is also suggested that the greater water capacity of treated plants buffers them against deleterious changes in leaf relative water content and water potential under conditions of moderate stress. INTRODUCTION Growth and yield of sugar beet are increased by sodium chloride (Draycott, 1972). Sodium accumulates mainly in the leaves where it is thought to improve water balance and reduce wilting. The evidence for this from field experiments is contra dictory. Sodium fertilizer may have no visible effects on wilting or it may increase or decrease it depending on the season (Draycott and Farley, 1971; Farley and Draycott, 1974; Durrant, Draycott, and Milford, 1978). Similarly, Draycott, Durrant, and Webb (1974) found no statistical interaction between the effects of sodium fertilizer and irrigation on sugar yield and concluded that sodium was unlikely to have affected growth by changing plant water status. But subsequent reappraisal of this and other of their data has shown that sodium and soil moisture do interact to affect leaf water balance and growth (Durrant et al., 1978). Few detailed measurements have been made of the effects of sodium on plant water status. Durrant et al. (1978) showed that sodium increased the relative water content, water potential, and diffusive conductances of leaves only under conditions of moderate soil moisture deficit; it had no effects when deficits were small and decreased leaf water potentials when drought was severe. A major effect of sodium is to increase leaf area (Draycott and Farley, 1971). Lawlor and Milford (1973) found with plants in solution culture that sodium produced a small, but signi ficant, change in leaf turgor potential sufficient to have increased leaf expansion. This content downloaded from 157.55.39.35 on Mon, 29 Aug 2016 05:16:02 UTC All use subject to http://about.jstor.org/terms Milford, Cormack and Durrant—Salt and Water Growth Effects 1381 Even so, the large increases in cation and water content caused by sodium in leaves are rarely accompanied by significant changes in leaf water or osmotic potentials (Lawlor and Milford, 1973; Durrant et al., 1978) so it is not clear how turgor is increased. The work reported here investigated the influence of sodium on the water status, growth, and physiology of leaves of soil-grown sugar beet subjected to a range of soil water potentials in controlled environments. MATERIALS AND METHODS The experimental plants were a commercial monogerm cultivar (Bush Mono G) of sugar beet (Beta vulgaris L.), each grown for 15 weeks in a glasshouse in 5 kg of Ashley Variant, a gravelly sandy clay loam from Broom's Barn Experimental Station, Suffolk containing (kg1 air-dried soil) additional Ca(NC>3)2 (0-24 g), NH4H2PO4 (0-12 g), K2SO4 (0-30 g), and H3BO3 (0-4 mg). Half the plants were given NaCl (0-60 g kg-1 soil), the rest none. Three days before the start of the experiment the plants were placed in a growth room maintained at a visible irradiance of 115 W m-2, a temperature of 15 °C, and an absolute humidity of 7-7 g m-3 during a 12 h day (equivalent to a saturation deficit of 680 Pa) and at 11 °C and 8-9 g m-3 (130 Pa) absolute humidity at night. After acclimatizing the plants, the soil was brought to pot capacity (water content 24 % of soil dry weight) and measurements were made on groups of plants, half grown with sodium and half without, at intervals during the 10 d required to dry the soil to a water content of around 6 % of soil dry weight at which the plants were severely wilted. On each occasion transpiration was estimated over a period of 2 h from the change in weight of pot and plant; because the soil was covered with a layer of polythene granules it was assumed that evaporation from the soil surface was negligible. At the end of the 2 h period a series of measure ments were made on two mature, fully expanded leaves on each plant, these usually being the fifteenth and sixteenth leaves produced. Leaf thickness was measured with a Mercer dial micrometer, diffusive resistance with a LI-COR sensor (Model LI-153) and meter, and gross photosynthesis measured by determining the uptake of radioactive carbon dioxide (Milford and Lawlor, 1975). Three groups of five 0-75 cm2 discs were punched from each leaf; relative water contents were measured by the method of Barrs and Weatherley (1962) on one group, carbohydrates measured as described by Milford and Pearman (1975) 011 the second group, and the osmotic concentration of the sap expressed from the third group measured with a Wescor C52 sample chamber psychrometer. The water potentials of the remaining parts of the leaves and of similar adjacent undamaged leaves were then measured, some with a pressure bomb (Scholander, Hammel, Hemmingsen, and Bradstreet, 1964) and some with thermo couple psychrometers (Lawlor, 1972). Turgor potentials were estimated as the difference be tween the psychrometrically measured water and osmotic potentials. Finally, the plants were removed from the pots, their leaf area and fresh and dry weights determined and sodium (Na+) and potassium (K+) contents of their parts measured by atomic absorption and emission spectrophotometry after dry ashing and acid extraction. Duplicate soil samples were taken from the top, middle, and bottom of each pot, their moisture contents measured, and their matric potentials determined by thermocouple psychrometry and a pressure membrane apparatus : the average of these samples was taken as an estimate of the water potential of the bulk soil. The experiment also contained two further groups of untreated and sodium-treated plants for analysis of plant growth. The soil of one group was allowed to dry out as above and in the other group it was maintained close to pot capacity by weighing and watering twice daily. Dry weights and leaf areas of these plants were measured at the start and end of the treatment cycle. The whole experiment was repeated twice with similar results, the data have been combined for presentation. RESULTS Plant dry weights and leaf areas and the sodium, potassium, and water contents of plant organs at the beginning of the drying treatment are given in Table 1. The sodium chloride treatment increased Na+ concentration in all organs 10-fold and decreased the K+ concentration by a small, but not stoichiometrically equivalent, This content downloaded from 157.55.39.35 on Mon, 29 Aug 2016 05:16:02 UTC All use subject to http://about.jstor.org/terms 1382 Milford, Cormack and Durrant—Salt and Water Growth Effects Table 1. Effects of sodium chloride (a) on dry weights, leaf areas, and sodium, potassium, and water contents of sugar beet at the start of a 10 d drying treatment and (6) on groivth in watered and unwatered plants Without sodium With sodium L.S.D. chloride chloride (P = 0-05) (a) At start of drying treatment Dry weight (g) Laminae 4-7 5-9 0-31** Petioles 2-5 2-7 0-10* Root 1-4 1-7 0-14* Plant 8-7 10-2 1-56* Water content Laminae 5-99 6-96 0-43** (g g-1 dry matter) Petioles 6-93 8-44 0-66** Root 4-56 5-18 0-64 NS Sodium content Laminae 0-24 1-64 0.172*** (mmol g_1 dry Petioles 0-07 1-12 0-074*** matter) Root 0-02 0-22 0-048*** Potassium content Laminae 1-26 0-98 0-164* (mmol g_1 dry Petioles 1-20 1-06 0-232 NS matter) Root 0-54 0-58 0-144 NS Number of leaves 12-5 12-0 1-21 NS Leaf area (dm2) 9-83 11-84 1-55* Leaf thickness (mm) 0-33 0-39 0-014*** Leaf succulence 2-86 3-47 Q-24*** (gwaterdnw2) (b) At end of drying treatment Unwatered plants Plant dry weight (g) 12-9 16-9 "2-13** Leaf area (dm2) 7-1 10-4 «1-56*** Watered plants Plant dry weight (g) 15-7 19-3 Leaf area (dm2) 10-5 12-4 NS, *, **, and *** indicate non-significance, and significance at the 5, 1, and 0-1% levels of probability, respectively. ° Least significant differences between means of both sodium chloride and watering treat ments. amount. It increased the dry weight of all parts of the plant, the leaf area, and the thickness and succulence of the leaves, i.e. water content per unit area (Jennings, 1976), but not leaf number. During the 10 d of the experimental drying period the soil moisture content decreased from 24 to 6 %, of soil dry weight equivalent to a change in matric potential from —20 kPa to —1-5 MPa (Fig. 1a). In this time the dry weight of sodium-treated plants increased by 90 % when continuously watered and by 65 % when unwatered, while the corresponding figures for untreated plants were 80 and 45 % respectively. Leaf areas of watered plants increased by 6 % irrespective of sodium treatment but those of unwatered plants decreased because their mature leaves died ; leaf area decreased by almost 30 % in untreated plants and by 10 % in sodium-treated plants. There was only a small change in matric potential with change in soil moisture content over the range 25 to 10 % in the sandy clay loam, i.e. from —20 kPa to Q. l 1 dry 1

Journal ArticleDOI
TL;DR: In this article, the polypeptide components of the reduced prolamin fraction (hordein) of barley seed proteins have been separated, before and after alkylation, by polyacrylamide gel electrophoresis using buffers containing urea and/or sodium dodecylsulphate (SDS).
Abstract: The polypeptide components of the reduced prolamin fraction (hordein) of barley seed proteins have been separated, before and after alkylation, by polyacrylamide gel electrophoresis using buffers containing urea and/or sodium dodecylsulphate (SDS). Alkylation of the protein with 4-vinylpyridine or acrylonitrile results in a considerable sharpening of the protein bands and some minor changes in the band pattern. The procedure has been used to compare the hordeins of the normal commercial varieties, Julia and Bomi, to those of a high lysine mutant of Bomi (Rise, 1508). Whereas the alkylated hordein fractions of Bomi and Julia contain SDS bands of apparent molecular weights 13 000, 16 000, 20 000, 30 000, 43 000, 51 000, 67 000, and 86 000, the mutant hordein fractions contain predominantly the low molecular weight (13 000, 16 000, and 20 000) and mol. wt. 51 000 bands. Further resolution of the fractions was obtained by two-dimensional electrophoresis using 6 M urea in glycine/acetate buffer at pH 4·6 as the first dimension and SDS in tris/borate buffer at pH 8·9 as the second. Separation of the Rise 1508 hordein in this system demonstrated that the mol. wt. 51 000 band contains several closely similar components.

Journal ArticleDOI
TL;DR: Counts of Aphis fabae Scop, eggs in winter and of the active stages in May on the spindle bush, Euonymus europaeus L., are used to predict the need for chemical control of the black bean aphid on spring-sown field beans, Vicia faba L.
Abstract: SUMMARY Counts of Aphis fabae Scop, eggs in winter and of the active stages in May on the spindle bush, Euonymus europaeus L., are used to predict the need for chemical control of the black bean aphid on spring-sown field beans, Vicia faba L. For the purposes of forecasting, most of England south of the Humber is divided into 18 areas for which separate forecasts are made. A level of 5 per cent of plants colonized on the SW. headlands of fields in early to mid-June is used as an economic threshold above which control measures are justified. From 1970 to 1975, area forecasts of the probability of attack were successful. According to the sampled fields there was considerable annual variation in the size of infestations, ranging from widespread, potentially damaging populations in 1973 and 1974 to very small populations in 1975. There was also considerable variation between areas: for example, in East Anglia and the East Midlands treatment was justified only in 1973 and 1974, whereas in Hampshire and Worcestershire/Herefordshire treatment was justified in all years except 1975. It was estimated that, from 1970 to 1975, control based on forecasting would have led to a gain of £11·4/ha over no treatment, and £3·8/ha over correctly timed routine preventive treatment applied annually irrespective of the aphid situation.

Journal ArticleDOI
TL;DR: In this paper, thermal fluctuations detected by thermocouples are employed as natural tracers to determine gas flow velocities in fire gases channelled under a ceiling, in the velocity range 1-5 m/s.

Journal ArticleDOI
TL;DR: In this paper, Haematozoa of British birds are described. But the authors focus on the Haematology of birds and do not discuss the distribution of Haematae.
Abstract: (1977). Haematozoa of British birds. Journal of Natural History: Vol. 11, No. 6, pp. 597-600.


Journal ArticleDOI
TL;DR: The capture efficiency was determined chiefly by insect type: Diptera 79–98%, Hymenoptera 60–83%, Homoptera 32–76%, Thysanoptera 27–62%, Acarina 12–40%.
Abstract: . 1. Capture efficiency was determined chiefly by insect type: Diptera 79–98%, Hymenoptera 60–83%, Homoptera 32–76%, Thysanoptera 27–62%, Acarina 12–40%. 2. Grass length also affected efficiency, but to a lesser degree. 3. Prolongation of the sampling period increased the proportions of some groups more than others. 4. Capture efficiency for any group was not affected by the number of individuals present. 5. Catch size did not vary with time of day. 6. The method was unsatisfactory for wet grass.

Journal ArticleDOI
01 Mar 1977-Virology
TL;DR: It is proposed that in the virus particle the single helical RNA strand is embedded at a radius of 3.3 nm in a protein coat comprised of approximately 3400 protein subunits, giving a total particle weight of 80 million daltons.

Journal ArticleDOI
TL;DR: Lysogenic and non-lysogenic cultures of R. trifolii were all sensitive to yeast extract, and such sensitivity, for strains of several species, was unrelated to effectiveness in nodulating host plants.
Abstract: A low concentration of yeast extract (0·1%) in liquid media favoured rapid growth and high percentage of viable cells in cultures of Rhizobium japonicum (CB 1809), R. lupini (WU 425), R. meliloti (SU 47), R. trifolii (TA1) and a cowpea strain (CB 756). Concentrations of yeast extract > 0·35% depressed viability and produced distorted cells in all strains except SU 47: TA1 was especially sensitive. When used at 0·5–1% (w/v), each yeast extract (Difco, Oxoid, Vegemite) or casein hydrolysate produced greatly enlarged abnormal cells of TA1, each containing several granules of poly-β-hydroxybutyrate and whorls of intracytoplasmic membranes, and showing greater internal disorganisation than that seen in root nodule bacteroids. Lysogenic and non-lysogenic cultures of R. trifolii were all sensitive to yeast extract, and such sensitivity, for strains of several species, was unrelated to effectiveness in nodulating host plants. Glycine inhibited growth of all strains tested. Several other amino acids occurring in casein hydrolysate inhibited TA1 strongly and induced formation of distorted cells and spheroplasts; this distortion was partly counteracted by adding salts of calcium or magnesium. In media with 0·1% yeast extract the use of mannitol, sucrose, lactose or galactose as alternative carbon sources, each at a concentration of 0·02–1%, did not affect numbers of viable rhizobia or cell shape in all strains tested.

Journal ArticleDOI
TL;DR: The best rates for maize were faster than the best rates of wheat when the measurements were made at 23 or 28 °C but at 13 or 18 °C the best rate of maize was not significantly better than wheat.
Abstract: Maize and wheat plants were grown in controlled environments with day temperatures of 13, 18, 23, or 28 °C. Leaves from maize grown at 23 °C photosynthesized faster than leaves from maize grown at 13 or 18 °C and, except when measured at 28 °C, faster than leaves from maize grownat28 °C; leaves of maize grown at 13 °C were yellow and photosynthesized at insignificant rates. Leaves from wheat grown at 18 ° or 13 °C had faster rates of photosynthesis than leaves from wheat grown at 23 or 28 °C. The best rates for maize were faster than the best rates for wheat when the measurements were made at 23 or 28 °C but at 13 or 18 °C the best rates for maize were not significantly better than the best rates for wheat. Leaves of maize that developed in the environment with 23 °C as the day temperature did not rapidly lose their green colour when transferred to the environment with the day temperature of 13 °C and the rate of photo synthesis of these leaves did not decline rapidly. However, new leaves expanding in the cooler conditions were yellow and not effective in photosynthesis. At 13 or 18 °C maize, a C4 plant, which photorespires slowly, did not photosynthesize more effectively than wheat, which photo respires rapidly. The maize did not produce its most effective leaves at 13 or 18 °C and its optimum temperature for photosynthesis was 23°C or higher. It may therefore be considered ill-adapted to the temperate climate.


Journal ArticleDOI
TL;DR: No major immigration was demonstrated during the investigation period, even when favourable winds from neighbouring countries occurred at times when the insect was abundant, and the major increases in catch were explained by population growth within the island, together with localised movements away from areas of high population density.
Abstract: A network of 51 pheromone traps was distributed throughout Cyprus for a period of seven months during 1972, and catches of males of Spodoptera littoralis (Boisd.) were recorded each day. The aim was to find whether Spodoptera adults were immigrating from elsewhere by mapping changes in their distribution and density in relation to current meteorological conditions, especially wind-flow patterns. No major immigration was demonstrated during the investigation period, even when favourable winds from neighbouring countries occurred at times when the insect was abundant. The major increases in catch in the island trap network were explained by population growth within the island, together with localised. movements away from areas of high population density.

Journal ArticleDOI
TL;DR: Fungicides, applied as a seed treatment or foliar spray, were used on up to 47 per cent of the crops assessed and were associated with a decreased severity of mildew, and it is estimated that in 1974 and 1975 at least 60 per cent the crops which received no fungicide would have given an economic yield increase following treatment for mildew control.
Abstract: SUMMARY Randomly selected crops of spring barley in England and Wales were sampled annually in July, when the grain was filling most rapidly, and the diseases affecting the flag and second leaves were assessed. Mildew was the most common disease in all years and was the most severe disease on both leaves, except in 1975 when it was slightly less severe on the flag leaf than yellow rust. Other frequently recorded diseases were brown rust, leaf blotch and, in 1972, 1973 and 1974, Septoria spp. Halo spot and net blotch were infrequent and generally not severe. Fungicides, applied as a seed treatment or foliar spray, were used on up to 47 per cent of the crops assessed and were associated with a decreased severity of mildew. It is estimated that in 1974 and 1975 at least 60 per cent of the crops which received no fungicide would have given an economic yield increase following treatment for mildew control. Annual estimates of national yield losses caused by mildew varied from 5·7 to 13·0 per cent: much greater than the 0·2 to 1·7 per cent estimated for brown rust or leaf blotch. Barley yellow dwarf virus was detected by transmission tests in the majority of the samples tested.

Journal ArticleDOI
01 Dec 1977-Polymer
TL;DR: In this paper, the in-plane c-axis orientation of crystallites was assessed from measurements of reflections from 105 crystal planes as in the method of Dumbleton and Bowles, and it was found that the crystallites tended to lie in two groups inclined at a small angle to the draw direction.


Journal ArticleDOI
01 Mar 1977
TL;DR: In this article, the authors investigated the role of evaporation, emulsion formation, spreading, and natural dispersion into the water column in the dissipation of oil spills at sea.
Abstract: Results are presented on factors relating to the dissipation of oil spills at sea, including evaporation, emulsion formation, spreading, and natural dispersion into the water column. For Ekofisk oil, 20% evaporates in about 7.5 hr and, while emulsion formation is as rapid as for Kuwait crude, the resulting viscosity is low and insufficient to allow interference with the natural spreading and dispersion rates. Spreading has 2 components. One is controlled by surface tension-viscous drag forces and the other is wind-induced. Together they contribute to the 2-dimensional dissipation of the oil so that subsequent oil concentrations in the sea are, of necessity, low. These concentrations were measured for naturally dispersing and chemically dispersed slicks. The chemically dispersed slicks were of 2 kinds. One was previously weathered for 3 hr, the other was of controlled thickness and was dispersed immediately. Resulting concentrations of oil in the sea are low and of short duration compared with those required to give observable effects in laboratory toxicity studies. No significant deleterious effects were found to result from the dispersion of oil slicks at sea using low toxicity dispersant chemicals; in any case, substantial quantities of oil can be expected to enter the sea before oil recovery operations can be mounted.

Journal ArticleDOI
TL;DR: Although all three inhibitors of photo respiration affected photorespiratory metabolism none stimulated photo synthesis and the results are consistent with the main release of C02 in photorespiration arising from the conversion of glycine to serine.
Abstract: The effect on the carbon metabolism of wheat leaf segments of certain inhibitors of photo respiration was studied. Sodium 2-hydroxy-3-butynoate supplied for 40 min resulted in accumulation of 14C in glycolic acid with only a 7% inhibition of photosynthesis ; when supplied for 90 min, photosynthesis was inhibited by 47%. When 14C02 was replaced by 1000 vpm 12C02, radioactivity in glycine decreased but increased more rapidly in sucrose with less release of 14C02. Isonicotinyl hydrazide (INH) inhibited photosynthesis from 14C02 by 50% and glycine replaced sucrose as the main product. When, after 15 min, 14C02 was replaced by 150 vpm 12C02, in the presence of INH less 14C02 was released, 14C in glycine decreased more slowly, and less [14C]sucrose accumulated. Glycidate (potassium 2,3-epoxypropionate) at 2 mM had no effect on photosynthetic rate and little effect on carbon metabolism ; 20 mM glycidate inhibited photosynthesis by 64% and resulted in less radioactivity in glycine, more in phosphate esters, and less 14C02 released. When photosynthesis was measured in 1000 vpm C02 the inhibitors gave smaller effects on metabolism than during photosynthesis from 150 vpm 14C02 but 20 mM glycidate still resulted in a 42% inhibition of photosynthesis. When U - [14C]glycerate was applied to leaf segments in air with 320 vpm 12C02 the total uptake of glycerate was not changed by the inhibitors. INH and glycidate both decreased the amount of glycerate metab olised. More 14C accumulated in glycine in the presence of INH and in phosphate esters and serine in the presence of glycidate. Hydroxybutynoate increased the production of glycolate from glycerate but did not affect the total amount of glycerate metabolised. Although all three inhibitors affected photorespiratory metabolism none stimulated photo synthesis. The results are consistent with the main release of C02 in photorespiration arising from the conversion of glycine to serine.