bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE EFFECT OF SUCROSE SPRAYING ON SYMPTOMS CAUSED BY BEET YELLOWS VIRUS IN SUGAR BEET
Authors: WATSON MARION A. 
Published: February 2008

When leaves of sugar‐beet plants infected with beet yellows virus were sprayed daily with 10% sucrose solution, yellowing symptoms were intensified. When glasshouse plants were shaded so that the light intensity was reduced to less than half of full daylight, yellowing symptoms were suppressed more completely on un‐sprayed than on sprayed plants. Spraying with 2–5 % sucrose solution had similar, but slightly smaller effects.Spraying with sucrose solution increased the carbohydrate content of the leaves, and the effects on symptom intensity and carbohydrate content were closely correlated. The regression coefficients of symptom score on total sugar content were nearly the same for shaded and unshaded plants. As the severity of symptoms was increased by supplying carbohydrate without change in the light conditions, it is concluded that light intensity affects symptom expression by varying the carbohydrate content of the leaves through its influence on photosynthesis.Sucrose spraying increased the yield of roots of healthy and infected plants, and most of the increase was sucrose. This shows that sprayed sugar was translocated to the roots from the leaves of both healthy and infected plants.Measurements of changes in carbohydrate content between evening and morning samplings confirmed that movement of carbohydrate out of infected leaves is not stopped by infection.
EFFECTS OF DARKNESS ON THE CONSTITUTION OF TOBACCO LEAVES AND SUSCEPTIBILITY TO VIRUS INFECTION
Authors: HUMPHRIES E. C. , KASSANIS B. 
Published: February 2008

An attempt was made to find the causes of increased susceptibility to virus infection when tobacco plants are kept in the dark before inoculation. The changes in certain nitrogen fractions, viz. insoluble‐N, amino‐N, amide‐N, ammonia‐N and nitrate‐N, and in dry matter and water content were followed in tobacco plants subjected to a period of darkness before inoculation with tobacco aucuba mosaic virus. Only nitrate‐N was strongly correlated with the susceptibility to infection, but the evidence suggests that the correlation is indirect and not causal.Dry matter and water content, determined either as dry matter percentage of fresh weight or measured separately on a leaf‐disk basis Ivere found to vary directly with variation in susceptibility.
THE INFLUENCE OF THE ENVIRONMENT ON SEED AND SEEDLING MORTALITY
Authors: HARPER JOHN L. 
Published: February 2008

Maize grains were exposed to 16–20 combinations of soil moisture and soil temperature (1–30 C.) for varying periods of time. Grains germinated readily in the wettest soils at 30 and 200 C, but germination was inhibited at the lower levels of soil moisture, and inhibited or delayed at the lower temperatures. Grains which failed to germinate in the soil were transferred to damp sand at 200 C. and the residual viability of the samples was determined. Mortality of grain was highest at combinations of temperature and soil moisture which just did not allow of germination. Soil conditions even more unfavourable for germination gave greater residual viability in the samples. The viability of dormant grains was more rapidly destroyed at high than at low temperatures although the reduction in viability continued longer at low temperatures, probably because of the slower drying of the soil.This mortality is interpreted in terms of pathogenic activity, and it is shown that mortality at high temperatures (20–35 o C.) is explicable on this general hypothesis. It is tentatively suggested that temperature and soil moisture conditions interact in selecting out and favouring the activity of specific populations of pathogens in the soil.
GRAZING OF WINTER CORN BY THE RABBIT (ORYCTOLAGUS CUNICULUS (L.)
Authors: GOUGH H. C. 
Published: February 2008

Observations on winter corn fields being severely grazed by rabbits showed that there was usually a typical pattern of damage when the source of the rabbits was from one direction. The part of the field nearest the source of rabbits was grazed for a long period and usually failed, the part farthest from the source of rabbits was grazed lightly or not at all and usually yielded well and the central section was intermediate. The effect of severe grazing was to delay plant establishment by retarding or preventing the formation of secondary roots and tillers, so that many plants ultimately died and the survivors were small and backward.Small plots protected by wire netting were used to demonstrate and investigate the effects of grazing, but there was no evidence that the shelter provided by the netting itself in the absence of rabbits directly improved growth within the cages. Artificial defoliation, unless it was very drastic, was not an adequate substitute for rabbit grazing, though this technique was used to confirm a field observation that oats were more susceptible than wheat to this type of damage. Some of the practical implications of the observations and experiments are discussed.
FURTHER OBSERVATIONS ON THE PATHOGENICITY OF CALONECTRIA RIGIDIUSCULA (BERK. & BR.) SACC. TO THEOBROMA CACAO L
Authors: OWEN HAROLD 
Published: February 2008

Quantitative data are provided for the occurrence of Calonectria rigidiuscula and other fungi in occluded Mirid lesions and other sites in shoots of cacao plants. Mirid lesions appear to be particularly favourable for the development of C. rigidiuscula. The fungus also occurs as a saprophyte on cacao pods, and as a wound parasite in woody plants other than cacao; it was successfully introduced into plants of varied affinities by inoculation. C. rigidiuscula spreads from inoculations in cacao stems much more rapidly than other fungi. The results confirm that it is the most important fungus infecting Mirid lesions and causing dieback of cacao in West Africa.Inoculation tests with a range of Amelonado and Trinitario clones suggested that the clones vary in their susceptibility to C. rigidiuscula, but the plant‐to‐plant variation was too great to conclude that any one is highly resistant. Various types of introduced cacao were also tested; preliminary experiments indicate that certain types of Upper Amazon cacao may be resistant, but they need further investigation.
THE BIOLOGY OF THE TWO COMMON STORAGE SPECIES OF ORYZAEPHILUS (COLEOPTERA, CUCUJIDAE)
Authors: HOWE R. W. 
Published: February 2008

Oryzaephilus surinamensis (L.) and O. mercator (Fauv.) are distinct species which do not interbreed; they can be distinguished by the relative lengths of eye and temple and by the male genitalia. Both species are imported into Britain, O. surinamensis chiefly on cereal products and O. mercator chiefly on oilseed products. O. mercator is killed by cold in Britain, but O. surinamensis can survive and not infrequently becomes a pest.Eggs hatched at temperatures from 17·5 to 40°C. Egg mortality was high below 20°C. and above 37·5°C. Low humidity also increased egg mortality but did not affect the length of the instar which was shortest at 35°C. and above. On wheat‐feed, the larva of O. mercator grew more slowly than that of O. surinamensis and was more sensitive to low humidities. The optimum for O. mercator was about 30–32·5°C. and that for O. surinamensis about 3–35°C. Low humidity increased the length of the larval period, and at 10% R.H., O. mercator died outside the range 25–32·5° C. The shortest pupal period was observed at over 35°C. On coconut meal at 30°C. and 70% R.H., O. mercator grew faster than O. surinamensis, which could not grow on this food at lower humidities. O. mercator grew more slowly on this food than on wheatfeed. Neither species completed development on groundnut meal unless yeast powder was added.The usual number of larval moults before pupation was three, but a few individuals had four or two. The longer larval period of O. mercator is explained partly by the individual instars being slightly longer than in O. surinamensis and partly by the increased tendency for the latter species to have only two larval moults.The preoviposition period of both species at 30 and 33°C. was 3–8 days, usually about 5. O. mercator reached a peak of three eggs per female per day and O. surinamensis of 6–10 per female per day by the end of a week and maintained these rates for a month, laying about 200 and 375 eggs per female respectively. About 95% of eggs hatched.Both species can increase rapidly in the tropics, but neither can grow very quickly in unheated stores in Britain. O. surinamensis is a pest because it can survive in large numbers in the fabric of warehouses and multiply rapidly when warm or actively heating produce becomes available.
INVESTIGATIONS ON RESISTANCE TO DISEASE AMONG SPECIES OF THE GENUS AVENA
Authors: WILLIAMS WATKIN , VERMA U. N. 
Published: February 2008

A collection of fifty‐three samples representing diploid and tetraploid species of the genus Avena was tested for resistance to three races of crown rust (Puccinia caronata avenue) and two races of stem rust (P. graminis avenae).Resistance to some races of the two rust species was confined to one sample of subsp. strigosa and two samples of subsp. barbata of A. strigosa. Sample no. 20, representing subsp. barbata, alone possessed resistance to all the races of both rust species. This material had previously been shown to be resistant to six races of smuts (Ustilago spp.). Genotypes possessing combinations of resistance to a wide range of pathogens appear to be very rare, and intra‐specific variation in respect of these characters is so great, that taxonomic classification cannot be used with any degree of certainty to discover sources of resistance to disease.The discovery of widespread resistance in a sample of the tetraploid subsp. barbata offers possibilities of the direct transference of genes to the cultivated species, thus dispensing with the need to synthesize amphidiploid bridging forms.The reaction of the hexaploid variety, Richland, to stem rust proved to be sensitive to temperature. Resistance mechanisms which are subject to environmental influences are considered to be less effective in combating the evolution of new races of the pathogen.
OBSERVATIONS ON THE EMERGENCE PERIODS, LARVAL POPULATIONS AND PARASITISM OF THE CABBAGE ROOT FLY (ERIOISCHIA BRASSICAE BCHE)
Authors: MILES MARY 
Published: February 2008

At Wye the overwintering generation of Erioischia brassicae emerged in captivity in a sharply defined period lasting from 4 April to 3 May 1954 and 75% (53 flies) emerged from n to 19 April.The emergence period for first‐generation flies in 1954 was from 28 June to 24 September. There was no well‐defined peak period; flies emerged almost every day from 28 June to 16 August, with the highest numbers (11 flies per day) on 16–17 July and the greatest concentration of emergences (76 flies, 41%) from 11 to 21 July. In 1955, first‐generation flies emerged from 24 June to 23 August, with a peak emergence period from 6 to 16 July when 50% (348 flies) emerged. The differences between the times of peak periods of emergence in the 2 years were associated with differences in temperature in June and July; cooler weather appeared to delay emergence.Counts of first‐generation larvae and puparia of E. brassicae in the latter half of June 1955 showed average populations of 59 per plant with a maximum of 132 per plant. Counts after exposure to attack during July and from mid‐August to November showed an average infestation of less than two per plant. Plants exposed to attack from mid‐May onwards until December showed average populations of 15 puparia per plant only two of which were viable. This gave further evidence that high infestation by E. brassicae occurs only in spring.Larvae and puparia collected in June were allowed to complete their development in captivity. In 19–54 the emergences from 350 puparia were as follows: 188 flies (54%); 145 (41%) Trybliographa rapae Westw., a Cynipid (Hymenoptera) parasite; and 17 (5%) Aleochara bilineata Gyll., a Staphylinid beetle parasite. In 1955 the emergences from 990 puparia were 693 (70%) flies, 296 (30%) Trybliographa rapae and one Aleochara bilineata. The samples consisted of larvae and puparia in a ratio of about 3 : 1 and were therefore biased in favour of Trybliographa rapae. Observations on dates of emergence showed that in samples consisting wholly of viable puparia drawn after mid‐July, there is likely to be a bias in favour of the parasites because the peak of emergence of first‐generation flies has already passed.
THE EFFECT OF ORGANOPHOSPHORUS INSECTICIDAL SPRAYS ON THE GROWTH AND PHOSPHORUS CONTENT OF BRUSSELS SPROUTS
Authors: THORNE GILLIAN N. 
Published: February 2008

No evidence was found that the insecticides schradan or demeton directly increase the growth of plants. The dry weight of Brussels sprouts plants grown in soil supplying little phosphorus was unaffected by spraying six times with schradan or demeton, or with sodium phosphate Solution supplying the same amount of phosphorus as the insecticides. The dry weight of larger plants grown in soil supplying more phosphorus was unaffected by spraying with demeton or inorganic phosphorus Solutions; schradan spray decreased it in one experiment but not in the other.Spraying with schradan, or with the equivalent amount of phosphorus as sodium phosphate, in one experiment increased the phosphorus content of plants grown in soil supplying little phosphorus. With high phosphorus supply in the same experiment, sodium phosphate Solution, but not schradan, increased phosphorus content of the plants slightly, but not significantly. Phosphorus content was not affected either by schradan sprays in the other experiment or by demeton sprays in both experiments.
INVESTIGATIONS REGARDING THE NATURE OF THE INTERACTION BETWEEN IRON AND MOLYBDENUM OR VANADIUM IN NUTRIENT SOLUTIONS WITH AND WITHOUT A GROWING PLANT
Authors: WARINGTON KATHERINE 
Published: February 2008

Iron offset the toxicity of molybdenum or vanadium in nutrient solutions more effectively when it was supplied at the same time as the molybdenum or vanadium than when it was given separately in alternate 3‐day periods.Allowing nutrient solutions of pH 4.6 containing high concentrations of iron, with or without vanadium, to stand for 4 days before use did not delay the restoration of colour to chlorotic plants, but even z days' standing reduced the iron content of their roots and the vanadium content of both shoot and root. The presence of vanadium had little effect on iron uptake.In parallel experiments with molybdenum, standing the solutions for 7–9 days before use delayed colour recovery, but shorter periods had no effect. Standing for z days or longer greatly reduced the iron content of the root, but the molybdenum content was unaffected or increased. High molybdenum greatly increased the iron in the root, but had little effect on that in the shoot.Precipitation of iron in the nutrient solution was delayed by high concentrations of either ammonium or sodium molybdate if the initial pH was 4.6, but not if it was 6.6. Vanadium had no influence on the precipitation of iron at pH 4.6.At least part of the compensating action of iron on molybdenum or vanadium toxicity would appear to take place outside the plant.
THE PRODUCTION OF ANTIBIOTICS IN SOIL
Authors: WRIGHT JOYCE M. 
Published: February 2008

Extracts of the coats of seeds inoculated with Trichoderma viride, Penicillium frequentans or P. gladioli and sown in soil contained antibiotics, identified by paper chromatography as gliotoxin, frequentin and gladiolic acid respectively. Three actinomycetes, Streptoniyces griseus, S. venezuelae and S. nureofaciens failed to produce an antibiotic in the coats of seeds sown in either John Innes potting compost or a calcareous soil.When uninoculated pea seeds were sown in a soil in which an unintroduced gliotoxin‐producing strain of Trichoderma viride was growing vigorously, gliotoxin was detected in the seed coats.
STUDIES ON THE UPTAKE AND TRANSLOCATION OF STREPTOMYCIN BY PEACH SEEDLINGS
Authors: DYE M. H. 
Published: February 2008

Measurements of the antibiotic activity in the foliage of peach seedlings, kept with their roots in mineral nutrient solutions containing streptomycin, showed that streptomycin passed into the foliage and sometimes reached concentrations above those of the solutions surrounding the roots. The amount of the antibiotic in leaves varied with the time that roots were kept in the solutions and with the streptomycin concentrations of the solutions. Lower leaves contained much more than upper leaves.Adding macerated leaf tissue to streptomycin solutions decreased the amount of streptomycin detectable in the supernatant liquid more than could be accounted for by dilution or alteration of pH.Streptomycin first affected plants by decreasing apical growth, but at higher concentrations it caused chlorotic and necrotic areas on leaves and stems.
THE EFFECT, ON OYSTER SPATFALL, OF CONTROLLING BARNACLE SETTLEMENT WITH DDT
Authors: WAUGH G. DUNCAN , ANSELL A. 
Published: February 2008

During the summer of 1955 experiments were made with DDT to control barnacle fouling of oyster spat collectors. Results showed that effective control of barnacles on artificial collectors doubled the yield of oyster spat. Shell cultch treated in the same way gave less conclusive results, partly because of the poor spatfall experienced.Oyster spat on treated artificial collectors were approximately 40% bigger, at the end of 2 1/2 months, than those on controls. Evidence from shells, however, indicated that DDT initially inhibited the growth of oyster spat. Apparently spat become stunted in natural conditions, because they are unable to compete effectively for food with the dense barnacle populations. Competition amongst barnacles themselves also causes stunting.The dense population of Elminius modestus on the east coast oyster grounds may have a long‐term effect on both the yield and growth of oysters.
THE ANTI‐ESTERASE ACTIVITY OF PARATHION AND SOME RELATED ORGANOPHOSPHORUS COMPOUNDS
Authors: STRINGER A. , FIELDING A. H. 
Published: February 2008

The in vitro activity of cholinesterase and acetylesterase of two insect species‐ Locusta migratoria migratorioides R. &F. and Calandra granaria L.—has been examined.There appear to be two distinct enzymes present, and in both insects their activities are at comparable levels and their inhibition by the organophosphorus compounds examined are also similar.Compounds possessing the phosphoryl group have high inhibitory activity and those with the thiophosphoryl group have low activity in vitro.
THE CYST OF THE POTATO‐ROOT EELWORM (HETERODERA ROSTOCHIENSIS WOLLENWEBER) AS A HATCHING UNIT
Authors: ELLENBY C. 
Published: February 2008

Two series of experiments are described: in one, the hatching of half and whole cysts is compared, in some cases after they have been subjected to tryptic digestion; in the second series, the hatching of free eggs is considered.Total emergence from halved cysts was very much greater than that from intact cysts. Emergence from trypsin‐treated halved cysts was greater than emergence from control halved cysts, suggesting that the enzyme affects the egg shell or the larva inside; it is possible, however, that the enzyme also affects the cyst wall, for treated whole cysts shrink more rapidly and to a greater extent when exposed to air.Total emergence from trypsin‐treated whole cysts did not differ significantly from that of untreated whole cysts, unlike previous findings (Ellenby, 1946 a); however, emergence began sooner from these cysts. Halving the cysts also resulted in earlier emergence, the biggest effect being produced by a combination of both trypsin and subsequent halving.The variability shown by the intact cysts was considerably greater than that shown by the halved cysts; halving the cysts reduced the coefficient of variation from 0·55 for whole untreated cysts, to 0·19 for untreated halved cysts, and to 0·13 for trypsin‐treated halved cysts. Apparently some of the variability in emergence, like the limitation of total emergence, is bound up with the nature of the cyst as a more or less closed system.In two experiments the hatching of eggs freed from half‐cysts was compared with that of eggs in their fellow intact halves. In one experiment there was no difference; in the other it was possible to show that a higher proportion of free eggs hatched. Evidently factors limiting hatching may operate among eggs in a mass, even though they are no longer completely enclosed in a cyst.
THE INFESTATION OF WINTER LETTUCE BY APHIDS AND ITS CONTROL
Authors: SMIETON M. J. , MONTGOMERY N. 
Published: February 2008

Observations have been made on the infestation by aphids of winter lettuce at Imperial College Field Station, Slough, for the seasons 1947–8 and 1949–54. The effects of transplanting and of the use of insecticides have been studied.Plants drilled in September where they were to mature were ready for cutting a little earlier than those transplanted in November, but in years when aphids were numerous the drilled lettuces were heavily infested and very few of them hearted.The infestation of young crops varied from year to year; in some winters it fell to a low level, in others it increased rapidly and persisted with serious effect on the crop. In some years lettuce mosaic virus was also prevalent. The dominant aphid species was Nusonovia ribis‐nigri (Mosley).An early and persistent attack, even in the absence of virus disease, much reduced the number of hearted plants and their average weight. A late attack by winged aphids in early spring sometimes spoilt fully hearted lettuces.Dipping the plants in nicotine solution at the time of transplanting in November reduced aphid infestation; dusting with benzene hexachloride proved more effective.If transplanting was delayed until February or March a relatively clean crop could be produced by insecticide treatment, but losses from fungal disease were usually high.
METHODS FOR THE STUDY OF BLOWFLY POPULATIONS
Authors: MACLEOD JOHN , DONNELLY JOSEPH 
Published: February 2008

The variance of groups of traps sampling the blowfly populations of areas of different degrees of complexity is examined from data for three representative types of pasture—semi‐arable, reclaimed peat bog, and upland sheepwalk.For mean catches of under twenty flies the coefficient of variation was less for limited areas of homogeneous vegetational cover than for larger areas and greater diversity of vegetation; at intermediate mean levels the difference was negligible, hut it reappeared at mean levels of 40 and upwards.Throughout the range of catches examined the variance was much greater than the mean. For very low catches even the standard deviation exceeded the mean, and at no level of mean was it less than 40%.Even for uniform areas such as association fragments the high variance made results with less than six traps difficult to interpret, and ten or more traps are advised.Two methods of comparative sampling of populations are discussed—stratification of the area to be sampled into subunits of relatively uniform vegetational or edaphic facies, and random distribution of the traps over the whole area. For the mean catches by these methods standard regression lines are suggested, from which variance estimates may be made when comparing observed means. Both regressions consist of two straight lines, the lower in each case having a steeper slope. The lines are:Sections S.D. =x̄+ 1 and 0·5x̄+7.Subsection blocks S.D. = 0·8x̄+ 1 and 0·4x̄+9