bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE ORIGIN OF POLLEN IN LAKE SEDIMENTS: AN ENCLOSED LAKE COMPARED WITH ONE RECEIVING INFLOW STREAMS
Authors: PENNINGTON WINIFRED 
Published: May 2006

SummaryThe contribution from inflow streams to pollen in lake sediments was examined by comparison of percentage and absolute pollen data from sediment cores taken from two small lakes (5 and 10 h) within the same lowland region of south Cumbria; one in an enclosed basin (a large interdrumlin hollow) and the other receiving streams. The vegetation histories of the last 7000 years, interpreted from percentage pollen analysis, were similar. Calculated rates of annual influx of pollen to the sediments were at all times lower in the enclosed basin; in it they agreed with present deposition into pollen traps from respectively forest, incompletely vegetated land, and grassland. These rates are accepted as estimates of the amount of pollen per unit area which annually reaches a small lake by deposition from the air. Differences between these rates and those to the open lake, for each successive vegetation type, give estimates of the contribution from streams to sediments of the open lake. This contribution constituted < 50 % of the total during the forest period and increased to > 80 % at the horizon of extensive forest clearance.In the open lake, parallel changes in pollen and geochemistry at this clearance horizon show that the source of increased pollen influx lay in organic soils (mor); distribution of the tracer pollen Ilex shows that these soils must have formed on this catchment after initial disturbance of primary forest, and thereafter constituted a source of pollen of ages older than the time of deposition in the lake. Disruption of the vegetation cover on this catchment by deforestation and ploughing appears to have increased permanently the rate at which streams transported sediment, including pollen, to the lake. Only in the enclosed lake do rates of pollen influx remain in equilibrium with vegetation changes recorded in the percentage data. In this lake, with a similar history of changing land use, there is no perturbation of rates of annual pollen influx.The absolute pollen data for Tilia cordata in the enclosed lake confirm for this site the distribution history suggested for this species by Pigott and Huntley (1978).
THE PAST AND PRESENT VEGETATION OF THE CAENLOCHAN NATIONAL NATURE RESERVE, SCOTLAND. I. PRESENT VEGETATION
Authors: HUNTLEY B. 
Published: May 2006

SummaryThe geology, climate and soils of the Caenlochan N.N.R. are briefly described. The flora is discussed and the results of a primary phytosociological survey are described. One hundred and ninety‐three relevés were collected from uniform stands of vegetation and analysed using phytosociological techniques. Thirty‐four noda are delimited: 9 of them are heath types, 3 are bogs, 9 are grasslands, 4 represent various types of cliff‐ledges and 9 are mires, springs, rills and wet flushes. The floristics and ecology of the noda are briefly discussed.The ecological and floristic interrelationships among the noda are discussed. An ordination of the noda using constancy data is used to illustrate these relationships and to identify the principal habitat gradients. Soil base‐status and soil moisture are seen to be of primary importance but the secondary importance of land‐use history in determining the present vegetation is also emphasized.
THE TRANSLOCATION OF 32P IN TWO SUBMERGED AQUATIC ANGIOSPERM SPECIES
Authors: WELSH R. P. H. , DENNY P. 
Published: May 2006

SummaryThe translocation of phosphorus as 32P was investigated in two species of rooted, submerged, aquatic angiosperm, Potamogeton pectinatus and Potamogeton crispus. Experiments were conducted in two forms of partition apparatus for periods of either 1 to 48 h or 6 to 10 days. The apparatus used for the shorter‐term experiments incorporated three compartments so that possible isotope leakage through seals could be critically distinguished from plant excretion. Results of autoradiography and of radioactive counting provide evidence for a circulation of 32P in these plants akin to that described for terrestrial plants but with slower rates of movement. Quantitative differences in rates and amounts of 2P transport in the two species are discussed in relation to their anatomy and ecological distribution. There was no evidence of excretion of isotope, following transport, in the experiments conducted.
THE EFFECT OF DIFFERENT INORGANIC NITROGEN SOURCES AND PLANT AGE ON THE COMPOSITION OF BLEEDING SAP OF PHASEOLUS VULGARIS
Authors: THOMAS R. J. , FELLER U. , ERISMANN K. H. 
Published: May 2006

SummaryThe composition of the bleeding sap N of Phaseolus vulgaris varied with the inorganic nitrogen source fed to the plant but was not changed by a fourfold difference in external nitrate concentration. Highest sap N concentration and fastest growth were observed in ammonium nitrate grown plants. With nitrate grown plants 60 % of the total sap N was inorganic nitrate‐N and 40 % organic‐N whereas with ammonium nitrate grown plants nitrate contributed 30 % to the total N and organic‐N 70 %. Virtually all of the N in the sap of ammonium grown plants was organic‐N. Allantoic acid was the major individual reduced N compound in the bleeding sap of plants fed with nitrate, ammonium or ammonium nitrate. During the development of the plant from seedling to mature plant with ripened pods, the concentration of N in the bleeding sap of nitrate grown plants decreased sharply initially and then gradually during pod formation; it increased again when the pods had ripened. Nitrate reductase activity of leaf extracts was correlated with nitrate content of bleeding sap and was not much affected by increases in reduced N compounds in the sap.
SORBITOL, A COMPATIBLE OSMOTIC SOLUTE IN PLANTAGO MARITIMA
Authors: AHMAD I. , LARHER F. , STEWART G. R. 
Published: May 2006

Summary Plantago maritima grown under saline conditions accumulates large quantities of sodium chloride. Salinity reduces tissue potassium, calcium and magnesium contents. Several enzymes from P. maritima are shown to be salt‐sensitive. In contrast to many other higher plant halophytes, P. maritima shows no accumulation of either amino acids or methylated onium compounds. High levels of the polyhydric alcohol sorbitol are however accumulated under saline conditions. The possible role of sorbitol as a compatible cytoplasmic solute is discussed.
1THE EFFECT OF GALACTOSE ON THE GROWTH OF LEMNA
Authors: DeKOCK P. C. , CHESHIRE M. V. , MUNDIE C. M. , INKSON R. H. E. 
Published: May 2006

SummarySolutions of 0·1% galactose were toxic to Lemna gibba in axenic culture. The toxicity was counteracted by glucose and exacerbated by ethanol. Plants showing toxicity accumulated large amounts of starch and showed a mineral analysis typical of ageing fronds.Radioactively labelled galactose was readily transformed to glucose by plants in toxic conditions. The distribution of activity suggests only a slight impairment of cellulose synthesis. Although hormonal disturbances are probably involved, the fact that galactose is toxic to both plants and animals suggests that a more fundamental aspect of metabolism is involved.
WINTER FIXATION OF NITROGEN IN SCOTCH BROOM (CYTISUS SCOPARIUS L.)
Authors: WHEELER C. T. , PERRY D. A. , HELGERSON O. , GORDON J. C. 
Published: May 2006

SummaryThe retention of green lateral branches by Scotch Broom allows nitrogen fixation to continue during mild winters. Tolerance of low soil temperatures is suggested to be a major factor contributing to the occurrence of winter nitrogen fixation.
THE EFFECTS OF BISULPHITE AND SULPHATE UPON PHOTOSYNTHESIS IN SPHAGNUM
Authors: FERGUSON P. , LEE J. A. 
Published: May 2006

SummaryThe effect of various concentrations of HSO3‐ and SO42‐ on photosynthetic oxygen evolution in Sphagnum spp. was studied. Almost instantaneous reductions induced by HSO3‐, the magnitude of which increased with concentration, were not reversed by additions of HCO3‐. SO32‐ had no effect on oxygen evolution. The effect of HSO3‐ was markedly pH‐dependent, being much greater at lower pH. 14CO2 uptake was less sensitive to HSO3‐ than O2 evolution; low HSO3‐ concentrations enhanced 14CO2 fixation but never increased O2 evolution. 14CO2 fixation in the dark was also inhibited by 0·1 mM HSO3‐ but enhanced by lower concentrations. The results are discussed in relation to known mechanisms of sulphite toxicity and to effects of sulphite upon growth of Sphagnum spp.
A NOTE ON AERATION AND AERENCHYMA IN THE RHIZOME OF BRACKEN (PTERIDIUM AQUILINUM (L.) KUHN VAR. AQUILINUM)
Authors: WATT A. S. 
Published: May 2006

SummaryThe tissues involved in the aeration of the bracken [Pteridium aquilinum (L.) Kuhn var. aquilinum] rhizome are briefly described and functionally tested. The aerenchyma functions only until maturation of the rhizome.In experiments with blocks of Gault Clay placed in a sandy soil the clay is penetrated by the rhizome without change in its diameter. The roots, however, are reduced in number, thickness and in length (max. 3 cm) to a degree regarded as inadequate for the maintenance of a plant wholly in clay.
ON THE THEORY OF EXPLOSIVELY DISPERSED SEEDS: A CORRECTION
Authors: SWAINE M. D. , DAKUBU T. , BEER T. 
Published: May 2006

SummaryAttention is drawn to an error in two earlier papers on seed dispersal (Beer and Swaine, 1977; Swaine and Beer, 1977). The correction of the error leads to quantitative changes in the earlier results which do not substantially affect the biological conclusions drawn.
POLLEN DIAGRAMS FROM NORTHUMBERLAND
Authors: DAVIES G. , TURNER J. 
Published: May 2006

SummaryPollen diagrams from four sites in Northumberland have been produced in order to study the impact of prehistoric man on the vegetation of the region since Neolithic times. The major vegetational changes have been radiocarbon dated at Fellend, Steng and Camp Hill Mosses, but not at Broad Moss.There is evidence at all four sites for small temporary clearances in the woodlands during the Bronze Age and also during the pre‐Roman Iron Age. These clearances were mainly for grazing and their frequency at a site accords well with the archaeological evidence for settlement.All the diagrams show a major clearance of forest, primarily for pasture, dated at Fellend and Steng Mosses to the time of the Roman occupation of the north‐east of England. At Camp Hill this clearance gave a late medieval date, but there is good reason for suspecting the sample may have been contaminated with 14C‐rich carbon. Regeneration of forest occurred some one to two hundred years after the withdrawal of the Romans. This has also been observed on diagrams from neighbouring counties, and indicates a post‐Roman period of economic stability.There was a further extensive clearance, dated at Fellend and Steng Mosses to the time of the Scandinavian settlement, and the diagrams show a late medieval recession in farming and a regeneration of woodland before the present landscape was created.Rates of peat accumulation were estimated from the radiocarbon dates at Fellend Moss, where it increased in late medieval times, and at Steng Moss, where it did so in the late Bronze Age.
SILICA DISTRIBUTION IN EQUISETUM HYEMALE VAR. AFFINE L. (ENGELM) IN RELATION TO THE NEGATIVE GEOTROPIC RESPONSE
Authors: SRINIVASAN J. , DAYANANDAN P. , KAUFMAN P. B. 
Published: May 2006

SummaryIn young growing Equisetum shoots silica deposition proceeds basipetally in the internodes. The surface of the mature internode, including the stomata, becomes encrusted with silica. Only young shoots with active intercalary meristems and very little silica deposition show a negative geotropic response. As the internodes mature, the difference in silica deposition between intercalary meristem and upper part diminishes so that the failure of mature internodes to respond geotropically is most likely due to significant silica deposition in the once active intercalary meristem sites.Initiation of negative geotropic curvature in young Equisetum shoots takes 36 to 48 h, and six to nine internodes are involved. Control of the geotropic response is auxin‐mediated as shown by experiments with the auxin transport inhibitors, triiodobenzoic acid (TIBA) and methyl‐2‐chloro‐9‐hydroxy fluorene (CFM, a morphactin). The former partially inhibited the response while the latter completely inhibited curvature.
ULTRASTRUCTURAL ASPECTS OF ENDOMYCORRHIZA IN THE ERICACEAE
Authors: BONFANTE‐FASOLO P. , GIANINAZZI‐PEARSON V. 
Published: May 2006

SummaryThe ultrastructural organization of endomycorrhizal hair roots of Calluna vulgaris has been studied in naturally infected plants by scanning and electron microscopy. Heavy fungal infection is present in, and limited to, cells of the root cortex. All intracellular hyphae have simple septa and associated Woronin bodies, characteristic of ascomycetous fungi. Penetrating hyphae are surrounded by a layer of inner host wall material. The host plasmalemma invaginates to surround the individual intracellular hyphae and it is separated from them by an interfacial matrix of varying thickness. No evidence of lysis or digestion of the intracellular hyphae by the host plant has been observed.
LICHEN METABOLISM
Authors: COWAN D. A. , GREEN T. G. A. , WILSON A. T. 
Published: May 2006

SummaryMetabolic studies were carried out on two lichen species (Ramalina celastri and Peltigera polydactyla) using 3HHO(g) and 14CO2. Incubations in the presence and absence of light at 100 % r.h. resulted in 3H and 14C labelling of a variety of compounds. Tritium fixation during darkness was determined quantitatively as 4.1 and 8.2 % of ‘light’ labelling (for P. polydactyla and R. celastri, respectively), and was localized predominantly in polyols, alanine, glutamic acid, glutamine, aspartic acid and γ‐amino butyric acid. Under similar experimental conditions, only trace amounts of 14C were found in sugar alcohols, whereas amino acids were substantially labelled. The dissimilarity between 3H and 14C labelling patterns has led to the conclusion that polyols synthesized in the absence of photosynthesis must be derived from other stored substrates within the thallus. The role of tricarboxylic acid (TCA) cycle‐related amino acids in lichen metabolism, and some potential synthetic modes of the unusual amino acid, γ‐amino butyric acid, are discussed.
INTERNAL FACTORS CONTROLLING THE RATE OF EVAPORATION FROM FRONDS OF SOME INTERTIDAL ALGAE
Authors: JONES HAMLYN G. , NORTON T. A. 
Published: May 2006

SummaryFactors controlling the rate of desiccation of single algal fronds were investigated using a diffusion porometer. Three species were compared—Laminaria digitata, Fucus serratus and Fucus spiralis. In all species the turgid thalli had a very high surface conductance (equivalent to a low resistance) to water loss. The rate of evaporation would therefore be controlled mainly by the environment, especially by the magnitude of the transfer resistance across the boundary layer. As the tissue of all species dried, the apparent surface conductance fell, though the conductance at any relative water content tended to be in the order Laminaria F. serratus F. spiralis. The more rapid the rate of desiccation, the lower was the surface conductance at any particular water content. This sensitivity to evaporation rate was much more pronounced in F. serratus than in the other two species and was less apparent in tissue stored for longer periods. An important factor contributing to water conservation in all three species was the shrinkage of tissue as water was lost, causing reduction of evaporating surface. The time taken for tissue of the three species to reach any given relative water content, when exposed to a particular environment, would be largely determined by the amount of water per unit area, which in saturated tissue, was highest in Laminaria, followed by F. serratus and then F. spiralis. The mechanism causing the lowered surface conductance was investigated using wet filter paper with or without the addition of mucilage or alginate gels.
THE USE OF SEED ISOENZYMES AS AN AID TO THE BREEDING OF FIELD BEANS (VICIA FABA L.)
Authors: GATES P. , BOULTER D. 
Published: May 2006

SummaryA rapid and economical method has been developed for identifying inbred lines and detecting crossing between them. It employs non‐specific esterase and glutamate‐oxaloacetate transaminase isoenzyme patterns of cotyledon extracts, separated by electrophoresis on acrylamide gels. Isoenzyme patterns were genotype‐specific and stable from plants grown in a range of environmental conditions. The potential value of these isoenzymes as markers for genotype identification and measurement of outcrossing is illustrated and discussed in relation to the breeding of field beans.
MEMBRANE BOUND INCLUSIONS IN EPIDERMAL PLASTIDS OF DEVELOPING SESAME LEAVES AND COTYLEDONS
Authors: PLATT‐ALOIA K. A. , THOMSON W. W. 
Published: May 2006

SummaryEpidermal plastids of young sesame leaves and cotyledons contain amorphous membrane bound inclusions similar to those found in the mesophyll. However, unlike the mesophyll inclusions which disappear during chloroplast development, those in epidermal plastids persist, even in fully mature leaves where a limited grana fretwork system develops.The limiting membrane of the inclusion is apparently continuous with both the tubular complex of light grown tissues and the prolamellar body of etiolated tissues as well as with the granal and integranal membranes. These associations, as well as a decrease in staining density of the inclusion with maturation, are interpreted as indications of a precursor‐product relationship of the inclusion and a grana fretwork.The coexistence of both grana and the (presumably) proteinaceous inclusion manifest the multifunctional capacity of plastids.
GROWTH AND INVERTASE ACTIVITY OF SUGAR BEET CALLUS
Authors: Mohammad A. M. S. , Collin H. A. 
Published: May 2006

SummaryThe nutrient requirements and cultural conditions for the initiation of sugar beet callus from the variety Kawe AA were established so that on a basic Murashige and Skoog nutrient medium containing 1‐0 mg l−1 kinetin, 1‐0 mg l−1 2,4‐D‐(2,4‐dichlorophenoxyacetic acid) and 4% sucrose a fast growing callus was produced. When the subculture period exceeded 3 weeks, the callus and medium became heavily pigmented. At 1.0 mg l−1 kinetin and 0.05 mg 1−1 2, 4‐D, root and shoot production were initiated and the plantlets were eventually isolated. Analysis of the invertase in callus showed both acid and alkaline invertase in the soluble and insoluble fraction. During a subculture the acid invertase activity remained constant but the alkaline invertase increased. There was no effect on the activity of increasing the concentration of sucrose in the medium. The pattern of invertase activity was similar to that found in other tissue cultures and dissimilar to that in intact plants where sugar accumulation was a notable feature.
NITRATE REDUCTASE ACTIVITY IN WHEAT (TRITICUM AESTIVUM L.) I. DISTRIBUTION THROUGHOUT THE LEAVES
Authors: HALLAM R. , BLACKWOOD G. C. 
Published: May 2006

SummaryThe distribution of nitrate reductase activity, as measured in vivo in the leaves of some spring wheats, was recorded. In plants grown under controlled conditions the highest activity was found in the youngest ligule emergent leaf. The acropetal part of this leaf had the highest level of activity until the leaf began to senesce. Changes in nitrate reductase activity in response to nitrate concentration in the nutrient solutions were also most pronounced in this tissue. Nitrate reductase activity in the basipetal part of the youngest ligule emergent leaf of two wheat varieties, grown at a range of nitrate levels, was followed throughout development. With a given variety the optimal nitrate concentration for development of enzyme activity was the same as that for growth, but this concentration differed between varieties.
NITRATE REDUCTASE ACTIVITY IN WHEAT (TRITICUM AESTIVUM L.) II. THE CORRELATION WITH YIELD
Authors: BLACKWOOD G. C. , HALLAM R. 
Published: May 2006

SummaryChanges in nitrate reductase activity in response to nitrogen treatment were measured in vivo in the basipetal part of the youngest ligule emergent leaf of wheat plants during early development. The relationship between these measurements and grain yield is reported for some spring wheats grown in a growth room and some field‐grown winter wheats. In both situations the c correlation of a linear regression of yield parameters and single measurements of nitrate reductase was found to be significant. Where split dressings of nitrogen were applied the seasonal mean nitrate reductase activity correlated well with yield.
FACTORS AFFECTING NITRATE REDUCTASE ACTIVITY IN SYNCHRONOUS CULTURES OF CHLORELLA*
Authors: Griffiths D. J. 
Published: May 2006

SummaryIn synchronous cultures of Chlorella emersonii and C. vulgaris (Brannon No. 1 strain), growing on an inorganic medium in a light/dark regime, nitrate reductase (NR) activity increases rapidly during the early stages of the light period and declines in the dark. Evidence is presented that the increase in NR activity requires photosynthesis and involves synthesis of enzyme protein. The two strains tested differ in the extent of dependence of their NR activity upon photosynthesis, the difference being related to their relative ability to undergo a fully heterotrophic mode of nutrition on a glucose medium in the dark. The effect of glucose, oxygen supply and of two inhibitors of phosphorylation upon the rate of decline in NR activity in the dark is reported.
THE CARBOHYDRATES OF THE LEAFY LIVERWORT, PLAGIOCH ILAASPLENIOIDES (L.) DUM.
Authors: Suleiman A. A. A. , Bacon J. , Christie A. , Lewis D. H. 
Published: May 2006

SummaryThe soluble carbohydrates of both Plagiochila asplenioides var. asplenioides and var. major consist of volemitol and a volemitol derivative, sucrose and a series of sucrosyl‐fructans and mannitol. Glucose, fructose and trehalose are present in trace amounts. Quantitatively, volemitol is the single most abundant compound but this is exceeded by total fructan. Starch is only a minor component and the neutral insoluble fraction consists of galactose, arabinose (major components), glucose, xylose and mannose (intermediate quantities) and fucose and rhamnose (minor components). Only starch and sucrose are depleted when tissue is kept in the dark overnight. Results are discussed in relation to the soluble composition of bryophytes in general.