bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies ON ENDOGENOUS LEVELS OF ETHYLENE AND AUXIN IN VICIA FABA DURING GROWTH AND DEVELOPMENT
Authors: EL‐BELTAGY A. S. , HALL M. A. 
Published: May 2006

SUMMARYEndogenous levels of ethylene, auxins and inhibitors have been followed during the course of development in two varieties of Vicia faba having markedly different growth habits. Increases in internal ethylene levels correlate well with the time of abscission of flowers or pods. No clear correlations were observable between any particular developmental process and endogenous levels of auxin or inhibitors, although there was some correlation between inhibitor levels and abscission. The role in the control of development of the three types of growth regulator studied is discussed.
ZINC AND COPPER UPTAKE BY AGROSTIS STOLONIFERA, TOLERANT TO BOTH ZINC AND COPPER
Authors: WU LIN , ANTONOVICS JANIS 
Published: May 2006

SUMMARYZinc and copper uptake by Agrostis stolonifera, tolerant to both zinc and copper, showed that different zinc levels had no effect on copper uptake and, conversely, copper had no effect on zinc uptake. There was, however, a strong interaction in the toxic effects of zinc and copper as measured by root elongation. The mechanisms of zinc and copper tolerance are therefore independent even when they act in the same individual.
I. NUMERICAL ANALYSIS
Authors: PENNINGTON WINIFRED , SACKIN M. J. 
Published: May 2006

SUMMARYResults are presented from Principal Components Analysis of three data matrices (pollen concentration per c.c., percentages of total pollen, and analyses for eight or nine chemical elements) of c. thirty samples from each of two profiles of lake sediment of Late‐Devensian age (15000 to 10000 years B.P.) from the Lake District and N.W. Scotland. The groupings of samples by their scores on the first two components of these Principal Components Analyses have been shown to produce similar divisions (zonations) to those originally produced subjectively by inspection of the percentage pollen diagrams. Though neither profile includes the classical Late‐Weichselian oscillation of pollen zones I, II and III, involving expansion of percentages of birch pollen within biogenic sediment between two minerogenic layers, numerical analysis has revealed in the data from both sites a pattern involving a threefold division with revertence, and another pattern of twofold division. The subjective zonation of the percentage diagrams clearly involved a process of mental integration of these two patterns. A plot of the scores of the samples on the first two components of the Principal Components Analyses groups the samples into clusters corresponding with the zones determined by inspection; similar results are obtained for each of the three Principal Components Analyses. This is interpreted as indicative of a close relationship between pollen and chemical data which can most readily be explained on the hypothesis that the boundaries of pollen zones represent the results of environmental changes which simultaneously affected soils and vegetation.
THE EFFECTS OF SENESCENCE ON THE PROTEIN COMPLEMENT OF PLASMA MEMBRANES FROM COTYLEDONS
Authors: LEES G. L. , THOMPSON J. E. 
Published: May 2006

SUMMARYThe protein composition of plasma membranes from young and senescent cotyledons of germinating Phaseolus vulgaris has been analysed by polyacrylamide gel electrophoresis after solubilizing the membranes in sodium dodecyl sulfate. Gels for membrane from 2‐day‐old tissue, an age still largely unaffected by senescence, showed eighteen bands ranging in molecular weight from 12,000 to 150,000. Of these, nine were sufficiently intense to register in spectrophotometric scans. Two fast‐running proteins of molecular weights 12,000 and 26,000 were quantitatively preponderant at this stage and comprised 11 and 25% of the total membrane protein respectively. With the onset of senescence during late germination the protein banding pattern changed. The sharp clearly defined bands characteristic of gels from young membrane were replaced by broad diffuse regions of protein stain in the gels from senescent membrane. In addition, the number of protein bands seen in the gels decreased between days 2 and 9 of germination. These observations suggest that membrane senescence in cotyledons is mediated, at least in part, by cytosol proteases acting on membrane proteins. Such action would lead to complete breakdown of some proteins and alteration of others.
HEXOKINASE ACTIVITY IN CULTURED SYCAMORE CELLS
Authors: FOWLER MICHAEL W. , CLIFTON ANNE 
Published: May 2006

SUMMARYCells of sycamore (Acer pseudoplatanus) grown in batch culture were disrupted by ultrasound. Slight variation in the length of time for which ultrasound was applied was found to produce major alterations in the ratio of ‘particulars’ to ‘soluble’ hexokinase activity. Variations in this ratio were also observed when the osmolarity of the extraction medium was maintained by the use of either Ficoll and Dextran 40 or mannitol. Growth of the cells was also accompanied by changes in the ratio of ‘particulate’ to ‘soluble’ hexokinase activity. The data provide confirmatory evidence that a proportion of the total hexokinase activity of the cell is associated with a particulate fraction but there is no evidence of its association with the cell wall.
SHADE‐INDUCED DAMPING‐OFF IN CONIFER SEEDLINGS
Authors: TAHER M. M. , COOKE R. C. 
Published: May 2006

SUMMARYThe mortality of seedlings of Pinus sylvestris, P. contorta, Picea sitchensis and P. exceha grown in natural soil under a range of light intensities was recorded over a 90‐day period. Low light intensities favoured damping‐off by soil‐borne necrotrophic fungi, principally species of Fusarium and Pythium, but aseptically‐grown seedlings survived a similar 90‐day period at these low intensities. The two Pinus species were more susceptible to damping‐off than the Picea species under all light treatments used but this difference was most marked at low light intensities. The influence of low‐light regimes on host‐necrotroph interactions is discussed.
SHADE‐INDUCED DAMPING‐OFF IN CONIFER SEEDLINGS
Authors: TAHER M. M. , COOKE R. C. 
Published: May 2006

SUMMARYSeedlings of Pinus sylvestris and Picea sitchensis were grown aseptically in sand culture for 30 days under a range of light intensities. Relative growth rates (whole seedlings and shoots) of Pinus sylvestris were greater than those of Picea sitchensis and significantly so at low light intensities, but their carbohydrate status was lower. The ethanol‐soluble carbohydrate/ethanol‐insoluble carbohydrate ratio was always higher in Pinus sylvestris than in Picea sitchensis and epidermal cell walls, lignification and vascularization in the hypocotyl were much less developed in Pinus sylvestris than in Picea sitchensis, especially at low light intensities. These findings are discussed in relation to the established susceptibility of Pinus sylvestris and resistance of Picea sitchensis to shade‐induced damping‐off by necrotrophic fungi.
THE EXTENSION ZONE OF MYCELIAL HYPHAE
Authors: STEELE G. C. , TRINCI A. P. J. 
Published: May 2006

SUMMARYThe lengths of the apical tapered region (the extension zone) of leading hyphae of six species were determined. Although the extension zones of different types of hyphae of Neurospora crassa varied from 2.2 to 29.2 μm, their extension zone expansion times (the time taken for a hyphal tip to expand from its minimum to its maximum diameter) were very similar. There was a direct relationship between extension zone length and the rate of hyphal extension. Extension zone length and hyphal diameter were not affected by temperature.
SCAPE ELONGATION IN NARCISSUS: THE INFLUENCE OF FLORAL ORGANS
Authors: HANKS GORDON R. , REES A. R. 
Published: May 2006

SUMMARYTo study the effects of floral organs on scape growth of narcissus, the spathe, perianth parts, paracorolla, anthers and gynoecium were excised from the bud in all practicable combinations, and growth regulators were applied to decapitated scapes.Spathe removal induced earlier flowering, and by the third day after treatment had reduced scape growth to 88% of that of intact controls. The removal of other parts (alone or in combination) had no additional effects on scape growth, except for gynoecium removal which reduced growth to 43% of that of intact controls after 3 days. Scape growth continued in all treated plants, however, and by day 23 the decapitated plants had grown 79% as much as the intact controls. The effect of gynoecium removal could largely be replaced by applied auxin; gibberellic acid was partly effective in restoring scape growth.
A NOTE ON ELLAGITANNINS AS INDICATORS OF EVOLUTIONARY STATUS IN DICOTYLEDONS
Authors: SPORNE KENNETH R. 
Published: May 2006

SUMMARYStatistical analysis confirms that, among dicotyledons, not only are leuco‐anthocyanins correlated with primitive characters but so, also, are ellagitannins. The most primitive dicotyledons, and especially those in tropical rain‐forests, tend to possess both kinds of tannin while the most advanced lack both kinds.
STIMULATION OF SEX ORGAN FORMATION IN PHYTOPHTHORA BY ANTAGONISTIC SPECIES OF TRICHODERMA
Authors: BRASIER C. M. 
Published: May 2006

SUMMARYTwo methods are described for the induction of sex organ formation in heterothallic Phytophthora species in response to Trichoderma, a volatile method and a direct inoculation (‘contact’) method.Tested for their ability to induce sexual reproduction in Phytophthora, isolates of Trichoderma koningii, T. piluliferum, T. polysporum and T. viride were found to be active, and isolates of T. hamatum, T. harzianum, T. longibrachiatum and T. pseudokoningii inactive. Response in Phytophthora was, without exception, confined to the A2 compatibility type. Response of different Phytophthora species, however, was more variable. All forty‐one isolates of P. cam‐bivora and P. cinnamomi tested responded to Trichoderma viride. Isolates of Phytophthora cryptogea, P. drechsleri, and P. nicotianae were apparently polymorphic for response. The black pepper form of P. palmivora responded, whereas P. palmivora forms 1 and 2 did not. A minimum induction period of c. 24 h exposure to volatiles of active Trichoderma was apparently necessary for consistent oogonial formation to occur. Oogonial formation occurred on a range of sterol‐containing media but not in their absence and over a wide range of conditions of temperature and light.Antagonism of Phytophthora cultures by active Trichoderma isolates was readily apparent both in the volatile and contact methods. The ability of Trichoderma isolates to induce a sexual response in Phytophthora was correlated with their ability to produce volatile antibiotics. Possible implications of the ‘Trichoderma effect’ for the taxonomy, reproductive physiology and genetics of Phytophthora spp. are considered.
STRUCTURE OF AERIAL AND SUBMERGED SCLEROTIA OF COPRINUS LAGOPUS
Authors: WATERS H. , BUTLER R. D. , MOORE D. 
Published: May 2006

SUMMARYSclerotia were formed in both aerial and submerged parts of the mycelium. In addition a layer of cells with pigmented thick walls (called brown matting) which differentiated at the air/agar interface was interpreted as an aspect of sclerotial behaviour since it was regularly formed by strains which produced submerged sclerotia and was composed of cells of similar structure to those of the outermost layer of the submerged sclerotium. Apart from producing sclerotia and oidiospores the cells of the aerial mycelium remained undifferentiated. In contrast, cells of the submerged mycelium, though initially indistinguishable from those of aerial hyphae, became individually differentiated within about 5 days of growth producing two further novel cell types; inflated cells containing glycogen, and hyaline thick‐walled cells. Submerged sclerotia were pale brown in colour, irregularly shaped and about 0.5–1.0 mm in diameter. The only structure which differentiated the submerged sclerotium from the submerged mycelium was the outer rind, a layer of cells with thick, pigmented walls. The central (medulla) region contained the same cell types in the same frequencies as the general submerged mycelium. In sharp contrast the aerial sclerotia were highly organized structures composed of distinct and compact tissues. Mature aerial sclerotia were dark brown to black spheroidal structures up to 0.5 mm in diameter. An outer layer of dead and moribund hyphae surrounded the main body of the sclerotium which was bilayered with an outer rind and inner medulla. The rind was multilayered and consisted of small cells with thick pigmented walls; intercellular spaces were cuticularized. The medulla was a closely packed tissue composed predominantly of hyaline thick‐walled cells of the same type as were encountered in the submerged mycelium.
THE GROWTH OF SECONDARY WOOD FIBRES
Authors: WENHAM M. W. , CUSICK F. 
Published: May 2006

SUMMARYCambial derivatives differentiating as xylem fibres characteristically increase in length by intrusive growth. Radial expansion of contiguous cells is required for this intrusive growth which, in consequence, is restricted to the expansion zone of the newly formed wood. The amount of intrusion depends primarily on the position of the tip of a fibre in relation to the lines of junction of tangential and radial walls in the surrounding cells; these lines of junction are potential sites for intrusive growth. In general, the greatest intrusion occurs where there are two potential sites for intrusion (usually one on either radial face of the fibre's tip); tips with one site show less intrusive growth and those with none show least of all. These arrangements may be modified by the configuration and activity of neighbouring cells.The hypothesis formulated is that the tip of a fibre secretes an enzyme which weakens the middle lamella between the cells adjacent to it; where this occurs, these cells, during their turgor expansion, round off from each other at the corners. The thin–walled tip of the fibre fills this space as it is created. The notion that the intruding tip pushes its way into the cellular matrix is contested.
THE RELEASE OF SPERMS FROM THE ANTHERIDIA OF POLYTRICHUM JUNIPERINUM HEDW.
Authors: PAOLILLO D. J. 
Published: May 2006

SUMMARYThe release of sperms from an antheridium of Polytrichum juniperinum occurs in two phases: a rapid phase, completed within a few seconds, and a slow phase, usually completed in 1–5 min. The rapid phase depends on an elastic contraction of the jacket that forces all or most of the sperms out of the chamber. The contraction has this effect because the base of the chamber contains a fluid that accounts for more than half the volume of the chamber. The fluid accumulates during maturation of the antheridium, and the jacket is stretched, storing the potential energy required for the expulsion of the sperms. The rapid phase of sperm release occurs in hypertonic solutions and in petroleum jelly, which confirms that the uptake of water by the antheridium is not required for the opening of the antheridium. The slow phase of release is distinguishable only when a substantial residue of sperms remains after the rapid release, and can be prevented by high osmotic concentration in the bathing medium. The slow release probably depends on the net uptake of water by osmosis, resulting from the relatively high osmotic concentration of the fluid in the antheridial chamber.
THE CLIMATIC CONTROL OF THE ALTITUDINAL DISTRIBUTION OF SEDUM ROSEA (L.) SCOP. AND S. TELEPHIUM L.
Authors: WOODWARD F. I. 
Published: May 2006

SUMMARYIt has been demonstrated that the decrease of temperature associated with an increase in altitude of 250 m is sufficient to reverse the outcome of competition between Sedum rosea (L.) Scop, and S. telephium L. ssp. fabaria Syme.Growth analyses of S. rosea and S. telephium in a range of temperature conditions have shown that the change in the outcome of competition is due to the marked increase in growth of 5. telephium and the insensitivity of s. rosea to an increase in temperature over the range recorded in the field.
SOME STATISTICAL PROBLEMS ASSOCIATED WITH DETERMINATIONS OF POPULATION PARAMETERS FOR HERBACEOUS PLANTS IN THE FIELD
Authors: HUTCHINGS M. J. 
Published: May 2006

SUMMARYThe use of regressions to predict weights of plants and methods for the assessment of skew‐ness of weight and height distributions in populations of Mercurialis perennis (L.) are discussed. Regression methods for estimation of plant weight are non‐destructive so that several weight estimates can be made at intervals on growing plants. Highly accurate predictions can be made from relationships between weight and dimensions. Non‐linear (quadratic) regressions based on the relationship between weight and hd2 (where h= stem height; d= basal stem diameter) were found to be most accurate in weight prediction. Use of the estimate of relative error to determine error in prediction is considered; when errors are normally distributed and emphasis is placed upon mean weights rather than individual weights, the degree of error is considerably reduced. Because the relationship between weight and hd2 changes during the season, a sequence of regressions should be used for weight prediction. The relationship may be disturbed through time by environmental fluctuations and will vary spatially with habitat and genotype. The problem of inflexions in the use of quadratics is encountered and a solution suggested which assumes that other regressions without inflexions in the sequence are correct.Histograms of weight and height distributions in plant populations do not allow accurate monitoring of changes in distribution through time. The moment coefficient is suggested as the best numerical estimate of skewness, since it is a sensitive measure and all the available data is utilized in its calculation. Pearson's second coefficient is less sensitive, and only utilizes the population mean and its median–a statistic which may be not sufficiently representative of the whole population to use in the calculation of skewness. Reasons are presented for the differences in the skewness values obtained by using these two coefficients.
THE RELEASE OF ORGANIC SUBSTANCES BY CEREAL ROOTS INTO SOIL
Authors: BARBER D. A. , MARTIN J. K. 
Published: May 2006

SUMMARYWheat and bailey plants were grown for 3 weeks in a constant environment chamber containing approximately atmospheric concentrations of carbon dioxide (0.03%) labelled with 14C. The roots of the plants were maintained under sterile or non‐sterile conditions in soil contained in sealed pots which were regularly flushed with air. This enabled the quantities of 14C‐labelled carbon dioxide produced in the soil by plant and microbial activity to be separately assessed. At harvest, the 14C and total carbon contents of the roots and shoots and of the water‐soluble and insoluble material present in the soil were measured.These procedures enabled both the amounts of organic materials released into soil by the roots of growing plants and the effects of micro‐organisms on the process to be determined. Under sterile conditions between 5 and 10% of the photosynthetically fixed carbon may be released by roots compared with 12–18% by the roots of plants growing in unsterilized soil. These latter values are equivalent to 18–25% of the dry matter increments of the plants. The results indicate also that the increased evolution of carbon dioxide by cropped as compared to fallow soils can largely be ascribed to the immediate utilization by micro‐organisms of substances released by roots.
THE SYSTEMATIC POSITION OF HICKLINGIA EDWARDII KIDSTON AND LANG
Authors: EDWARDS DIANNE 
Published: May 2006

SUMMARYRecent developments in the classification of the earliest vascular plants are discussed. The fertile parts of Hicklingia edwardii, a remarkably well preserved plant from the Middle Old Red Sandstone of Scotland, are described. It is concluded that this plant had lateral not terminal sporangia and may be assigned provisionally to the Zosterophyllophytina until more is known about its anatomy.
LEAF AIR SPACE SYSTEMS IN C3 AND C4 SPECIES
Authors: BYOTT G. S. 
Published: May 2006

SUMMARYMeasurements of airspace systems in monocotyledonous and dicotyledonous C3 and C4 leaves show that the C4 systems are generally smaller than those of C3 species. This anatomical feature is discussed in relation to PEP carboxylation and efficiency of water use.
ECOTYPE DIFFERENCES IN LEAF SURFACE PROPERTIES OF AGROSTISSTOLONIFERA FROM SALT MARSH, SPRAY ZONE AND INLAND HABITATS
Authors: AHMAD I. , WAINWRIGHT S. I. 
Published: May 2006

SUMMARYProperties of the leaf surface associated with wettability were studied in ecotypes of Agrosti stolonifera from salt marsh, spray zone and inland habitats. The maritime ecotypes retained much less salt than the inland ecotype after immersion in salt water. Retention of salt after spraying was highest by leaves of the inland ecotype and least by those of the spray zone ecotype. Differences in retention of salt can be correlated with differences in wettability (indicated by measurement of advancing contact angle) and these differences are, in turn, related to differences in the structure and distribution of extracuticular waxes on the surfaces of leaves of the ecotypes. The differences are considered to be adaptations to the environments in which the ecotypes grow.
THE UPTAKE OF PARAQUAT BY SOIL FUNGI
Authors: SMITH S. N. , LYON A. J. E. 
Published: May 2006

SUMMARYThe mucoraceous fungi, Mucor hiemalis and Zygorhynchus heterogamous, are considerably more susceptible to paraquat than the imperfect species, Aspergillus niger and Penicillium frequentans. The inhibitory effect of increasing levels of paraquat on hyphal extension, dry matter production and spore germination are much more marked in Mucor and Zygorhynchus. When grown on media containing paraquat, the mycelia of these species contain approximately twice as much of the herbicide as those of Aspergillus or Penicillium. Feeding (14C‐methyl)‐paraquat confirms that twice as much activity is accumulated by the susceptible species. It is suggested that susceptibility to paraquat is associated with the degree to which the herbicide accumulates in the mycelium.
THE DEVELOPMENT OF PATTERNING IN THE ALVEOLAR SEXINE OF COSMOS BIPINNATUS
Authors: DICKINSON H. G. , POTTER URSULA 
Published: May 2006

SUMMARYDevelopment of the sexine component of the pollen wall of Cosmos bipinnatus has been examined in detail. The pattern is first generated in the peripheral spore cytoplasm by ribosome‐coated tubules of membrane, themselves apparently ordered by microtubules. This arrangement of membranous tubules moves to the plasma membrane upon the surface of which are formed ridges of fibrillar material, themselves in register with the tubules beneath. This fibrillar material is laid down heavily in the sites destined to be occupied by spines. The patterning of the ridges is not analogous with that of the sexine, but of the alveoli contained within it. The early sexine itself is formed from precursors secreted by the spore cytoplasm, which encase the fibrils and polymerize. On release of the young spores from the tetrad, the fibrillar content of the sexine is lost, forming the network of alveoli characteristic of this type of pollen wall. The sexine also expands at this point and, since the nexine does not and the two layers are firmly attached to each other at the apertures, this growth results in the bowing out of the sexine in the non‐aperatural regions and, thereby, the formation of the cavea.