bluuebunny/crossref_metadata_2025_split huggingface dataset:
ISOLATION, STABILITY AND BIOCHEMISTRY OF A P‐FLUOROPHENYLALANINE‐RESISTANT CELL LINE OF ACER PSEUDOPLATANUS L.
Authors: GATHERCOLE R. W. E. , STREET H. E. 
Published: May 2006

SUMMARYCell lines resistant to growth inhibition by 10 μM DL‐p‐fluorophenylalanine (PFP) have been isolated from a stock cell suspension culture line of Acer pseudoplatarms L. One of the lines (X8) retained its resistance when serially subcultured in the absence of PFP. X8 could not be distinguished from the parent line in growth rate and biomass yield but in mixed cultures of the two lines, X8 cells progressively declined as a fraction of the cell population during serial subculture in the absence of PFP. The X8 line could be recovered from such mixed cultures by subculture to medium containing 10 μ(M PFP. Line X8 resembled the parent cell line in phenyl‐alanine (PA) pool size and in showing no evidence of discrimination between PA and PFP in protein synthesis. It differed from the parent line in exhibiting lower uptake of PFP and PA; at an appropriate level PA almost completely suppressed PFP uptake. X8 cells had a higher content of phenols and higher extractable activity of phenylalanine ammonia lyase (PAL); they actively degraded absorbed PFP. The problem of isolation of biochemical mutants from plant cell cultures is discussed.
CHEMICAL MODELS FOR PLANT WAX MORPHOGENESIS
Authors: CHAMBERS T. C. , RITCHIE I. M. , BOOTH MARGARET A. 
Published: May 2006

SUMMARYEvidence from recrystallization and surface diffusion studies is presented which suggests that the patterns of leaf cuticular wax deposits are mainly a function of the wax chemical composition. Wax probably arrives at the cuticular surface in a solvent which subsequently evaporates. Surface diffusion across the cuticle is not believed to contribute significantly to the wax growth process. Most of the compounds which comprise the wax, form plates or sheet‐like structures when crystallized from solution. In eucalypt leaf waxes, the naturally occurring plate waxes appear to be associated with the polar constituents of the wax. Natural waxes which occur as tubes probably contain a mixture of non‐polar compounds.
THE INFECTION PROCESS AND ULTRASTRUCTURE OF THE GUNNERA‐NOSTOC SYMBIOSIS
Authors: SILVESTER W. B. , McNAMARA P. J. 
Published: May 2006

SUMMARYThe two components of the Gunnera–Nostoc symbiosis were isolated, grown separately in culture and the association resynthesized in vitro. Both components develop normally when grown independently and Nostoc retains its ability to fix atmospheric nitrogen in symbiosis.Infection by Nostoc is initiated when the alga grows on mucilage produced by an apical papillate gland. The alga develops rapidly, growing between the papillae and finally penetrating thin‐walled meristematic cells at the base of the gland. Resulting nodules contain intracellular algal cells within a host membrane envelope. The algae are considerably modified in thylakoid distribution and shape, and have a very high heterocyst frequency. At later stages, the algae are enclosed in a thickened wall continuous with that of the host cell.
CONCERNING THE SINUOUS SHAPE OF LEAF EPIDERMAL CELLS
Authors: KORN ROBERT W. 
Published: May 2006

SUMMARYThe geometric features of the sinuous shape of intercostal epidermal cells of the upper epidermis of the leaf of the fern Dryopteris thelypteris (L.) were studied. These cells have an average and probability distribution for the number of anticlinal walls similar to those in tissues expanding in two dimensions as reported earlier. No angles between anticlinal walls were <90° or >180° thereby indicating that growth stresses do not alter the shape of cells during the final expansion stage of development. Both the number of convex and concave lobes per cell approaches the binomial expansion of a2(p(a)+q(b))4 while the formula a4(p(a)+q(b))8 describes the distribution for all lobes. Rare gametophtyes were found in which the cells were transformed into sporophytic, leafy types including xylem, spines and sinuous epidermal cells. The occurrence of this last feature indicates that the wavyness of epidermal cells can be achieved in an isolated layer of cells.The data best fit the hypothesis that each cell regardless of size and shape produces four growth centres, each of which arrives at a cell wall site by chance movements and forms either a concave or convex lobe.
TWO LATE‐GLACIAL (LATE DEVENSIAN) DIATOM ASSEMBLAGE PROFILES FROM NORTHERN SCOTLAND
Authors: HAWORTH ELIZABETH Y. 
Published: May 2006

SUMMARYTwo profiles of the diatom assemblages in lake sediments of Late Devensian age have been analysed in detail to substantiate a zonation based upon the diatom assemblages from the nearby Loch Sionascaig site, in northern Scotland. The profiles bear out the original divisions into three diatom assemblage zones and indicate some subdivisions; there is close correlation with stratigraphic, pollen and chemical changes. The Cam Loch assemblages did not include the planktonic phase found in the Sionascaig Diatom Zone 2 sediments of Allerød age, despite the proximity of the two sites and a geological location that would suggest a possibly richer environment.It is concluded that the best pioneer forms are those of cosmopolitan distribution and that in the benthos at least there was an alkaline environment with sufficient nutrient status for diatoms typical of present day eutrophic lakes to occur during the period of greatest diatom diversity. The open water planktonic environment probably remained nutrient‐poor with little diatomaceous plankton, a condition resembling some present‐day alpine lakes.The final cold phase of the late‐glacial is characterized by the temporary disappearance of many taxa and the presence of several indicator taxa. Solifluction of the surrounding land surface is indicated by the presence of some subaerial forms. This is also a feature of an earlier slight climatic recession indicated by correlation of pollen and diatom analyses and now correlated with the Bølling/Allerød stade.
POLAR TRANSPORT OF AUXIN THROUGH EMBRYOS
Authors: FRY S. C. , WANGERMANN ELISABETH 
Published: May 2006

SUMMARYHypocotyls of embryos from unripe and soaked ripe seeds of Phaseolus vulgaris and Acer pseudoplatanus are shown to be capable of transporting auxin. The transport is strongly polar and shows the characteristics of active transport in the basipetal but not the acropetal direction. A procambial cylinder and a few phloem elements have been formed in these hypocotyls.
A THEORETICAL ANALYSIS OF THE CONTRIBUTION OF ALGAL CELLS TO THE ATTENUATION OF LIGHT WITHIN NATURAL WATERS
Authors: KIRK J. T. O. 
Published: May 2006

SUMMARYA theoretical treatment of light attenuation within phytoplankton suspensions, developed in a previous paper, has now been extended to certain non‐spherical cells and colonies of diatoms, blue‐green and green algae.Procedures for calculating the mean absorption cross‐section for randomly oriented cells or colonies with the shape of cylinders, prolate spheroids or oblate spheroids, are described. The mean absorption cross‐sections at a series of wavelengths throughout the photosynthetic waveband are compared for model algae of various shapes, sizes and pigment compositions. The results clearly illustrate the principle that for a strongly absorbing algal cell/colony of a given volume, the more extended it is in space, the more effective it is as a light collector. The advantages of the more extended package are much less evident at wavelengths which are weakly absorbed.For algae of a compact, e.g. spherical, shape a large cell or colony captures much less light (of a wavelength which is strongly absorbed) than an equivalent volume of smaller cells. However, it is also true that a large particle of very extended shape, e.g. a long thin cylinder, can capture as much light as a greater number of smaller particles (of the same total volume) of more compact shape. This means that for purposes of light collection an alga is almost as well off when organized into long multicellular filaments as it would be if separated into a large number of single cells.Using the calculated values of mean absorption cross‐section the relationship between phytoplankton canopy structure and attenuation of photosynthetically active radiation (PAR) has been further investigated. Calculated values for the spectral distribution of light intensity, the total transmitted quantum flux, the vertical attenuation coefficients, and the increments in vertical attenuation coefficient per unit algal concentration, are presented for various model non‐scattering suspensions corresponding to common naturally‐occurring algae. The possible effects of turbidity on light attenuation in such systems are discussed.
EFFECT OF INFECTION BY MICROSPHAERA ALPHITOIDES (POWDERY MILDEW) ON CARBOHYDRATE LEVELS AND TRANSLOCATION IN SEEDLINGS OF QUERCUS ROBUR
Authors: HEWITT H. G. , AYRES P. G. 
Published: May 2006

SUMMARYAs infection of leaves of Quercus robur by Microsphaera alphitoides (powdery mildew) progressed, levels of total carbohydrate varied as first the rate of net photosynthesis declined and then an abnormal pattern of translocation was established. Infected leaves exported a smaller proportion of their photosynthate than did healthy leaves and imported a greater proportion of the photosynthate of healthy leaves on the same plant than did healthy leaves on healthy plants. Infection caused a decrease in the amounts of sucrose and insoluble glucose and an increase in amounts of glucose and fructose in leaf tissue. Evidence is presented that glucose and fructose were transferred to the fungus where they were converted to polyhydric alcohols and trehalose.
STUDIES ON DATA VARIABILITY AND THE USE OF POLYNOMIALS TO DESCRIBE PLANT GROWTH
Authors: ELIAS C. O. , CAUSTON D. R. 
Published: May 2006

SUMMARYThe question of which degree of polynomial should be fitted to plant data, for the purposes of growth analysis, has been considered in relation to the variability of the populations sampled. By means of actual and semi‐artificial data, it was shown that the variability of the samples taken at each harvest had a profound effect on the results of the tests of significance, when the relationship was fitted using individual observations. Significance tests performed on data of low variability resulted in over fitting, i.e. unrealistically high degrees were indicated as being most appropriate. Conversely, data of high variability were adequately fitted by lower order polynomials. In view of this, it is suggested that growth data should be fitted using harvest mean values, since in this case, the test of adequacy of fit is independent of the underlying population variability.
EFFECT OF ANAEROBIOSIS ON ACTIVITIES OF ALCOHOL DEHYDROGENASE AND PYRUVATE DECARBOXYLASE IN ROOTS OF ZEA MAYS
Authors: WIGNARAJAH K. , GREENWAY H. 
Published: May 2006

SummaryFlushing of nitrogen gas through culture solutions, for periods between 4 and 15 h, increased activities of alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC) in roots of intact maize plants (activities expressed as μmol mg protein−1 min−1). The activity of ADH was six to nine times greater than the activity of PDC.Under root anaerobiosis of intact maize plants, activities of both ADH and PDC were similar in all root segments taken between o and 37 mm behind the apex, but lower activities were found in the older root segments. These differences in enzyme levels between younger and older root tissues were affected neither by the light regime of the shoots nor by imposing anaerobiosis of the shoots as well as the roots; i.e. the differences in ADH and PDC activities found in root segments of different ages were not due to a superior oxygen supply from the shoots to the tissues near the shoot‐root junction.Roots of intact maize plants were also exposed to a range of oxygen concentrations, by flushing the nutrient solution with gases of different composition. ADH activities in the roots were highest with gas mixtures containing 8–13% oxygen, intermediate with pure nitrogen, and lowest when the solution was flushed with gas containing 20% oxygen.It is concluded that ADH activity cannot be used to diagnose the degree of oxygen deficiency to which maize roots have been exposed.
EFFECT OF WATERLOGGING ON GROWTH AND ACTIVITY OF ALCOHOL DEHYDROGENASE IN BARLEY AND RICE
Authors: WIGNARAJAH K. , GREENWAY H. , JOHN C. D. 
Published: May 2006

SummaryFlooding usually reduced shoot and root growth of barley. In addition, root growth was inhibited much more in flooding‐sensitive than flooding‐tolerant cultivars. Prolonged flooding resulted in larger increases in activity of alcohol dehydrogenase (ADH) in roots of flooding‐tolerant than flooding‐sensitive cultivars.Barley and rice were also grown in solutions flushed with gases of different oxygen concentration. In rice roots, high activities of ADH and pyruvate decarboxylase (PDC) were found only when the solutions were flushed with pure N2 gas. In barley roots, activities of ADH and PDC were highest using gases between 3 and 13% O2, lower with pure N2, and very low when using 20% O2.These results indicate that the level of ADH occurring in plant roots will be very dependent on experimental conditions, as for example root density. Species differences in activity of ADH might be mainly related to different oxygen tensions inside the roots, due in turn to differences in volume of aerenchyma and morphology of roots.
VESICULAR‐ARBUSCULAR MYCORRHIZA IN NATURAL VEGETATION SYSTEMS
Authors: KOUCHEKI H. K. , READ D. J. 
Published: May 2006

SummaryThe effects of vesicular‐arbuscular (VA) mycorrhizal association on the growth of Festuca ovina L. were assessed in soils sterilized by irradiation, in unsterilized soil, and in sand or sandpeat cultures with various nutrient additions.In irradiated soils, effects of mycorrhizal infection were masked by nutrient release which proceeded through the first 4 months of growth. However, 9 months after inoculation, significant increases of yield and phosphorus content occurred in the mycorrhizal plants. When the irradiated soil was recovered and re‐used to grow a second crop, marked increases of yield and P content were observed in mycorrhizal plants. Growth in unsterilized field soil was very slow despite the fact that all the plants were heavily infected.In sand culture, mycorrhizal plants were not significantly larger than non‐mycorrhizal controls when both were supplied with a full nutrient medium but differences between the two categories were evident when sand‐peat mixtures were supplemented with dilute nutrient medium and water.The results are discussed in relation to the possible significance of mycorrhizal infection in the field.
EFFECT OF MYCORRHIZAL INFECTION ON RESPIRATION AND ACTIVITY OF SOME OXIDASE ENZYMES OF ORCHID PROTOCORMS
Authors: BLAKEMAN J. P. , MOKAHEL M. A. , HADLEY G. 
Published: May 2006

SummaryInfection of protocorms of Dactylorhiza purpurella and a Cymbidium hybrid by an endophytic mycorrhizal fungus (Rhizoctonia sp.) led to a marked stimulation of respiration. Peak oxygen uptake often coincided with formation and digestion of pelotons. Treatment of protocorms with culture filtrates or mycelial extracts of the mycorrhizal fungus also enhanced oxygen uptake.Activities of polyphenol oxidase, ascorbic acid oxidase, peroxidase and catalase were greatly increased in infected protocorms. Peak activity often coincided with peak oxygen uptake and digestion of pelotons, except for peroxidase where peak activity occurred earlier.The orchid/endophyte system is compared with host/pathogen interactions in terms of the possible relationship between changes in enzyme activity and defence mechanisms.
THE INFLUENCE OF THE FREQUENCY OF WETTING AND DRYING ON THE RADIAL GROWTH OF THREE SAXICOLOUS LICHENS IN THE FIELD
Authors: ARMSTRONG R. A. 
Published: May 2006

SummaryThree lichen species were wetted with distilled water at different frequencies during August 1973 to July 1974. The radial growth rates of Parmelia glabratula ssp. fuliginosa and Physcia orhicularis thalli declined with increased wetting while the radial growth rate of Parmelia conspersa thalli increased with wetting frequency until ten experimental wettings per month but at fifteen wettings per month fell to a value near to the control. In the summer months wetting resulted in a decline in the radial growth of P. glabratula ssp. fuliginosa compared with the control but had little influence on the growth of P. conspersa and Physcia orbicularis. In the winter months, wetting had no significant influence on the radial growth of Parmelia glabratula ssp. fuliginosa, while the radial growth of P. conspersa increased and Physcia orbicularis declined compared with controls. These results are interpreted physiologically and in relation to the aspect distribution of the three lichens on rock surfaces.
CELL PROLIFERATION IN, AND DEVELOPMENT OF, THE APICAL MERISTEM IN ELONGATING LATERAL ROOTS OF VICIA FABA L.
Authors: MACLEOD R. D. 
Published: May 2006

SummaryVarious aspects of cell proliferation have been examined in the stele and in the cortex‐epidermis between 50 and 800 μm basal to the junction between the cap initials and the rest of the meristem, in newly emerged, 0.2 and 4 cm long lateral roots of Viciafaba following a i‐h exposure to tritiated thymidine. Cell proliferation was found to differ in the two tissues in a number of ways, e.g. cell doubling time was usually shorter and the growth fraction generally larger in the cortexepidermis than in the stele. Cell proliferation changed basally along each tissue, especially in the relative and absolute sizes of the various meristematic and quiescent cell fractions and in cell doubling and mean cycling times. It was concluded that the apical meristem expanded longitudinally as the lateral roots lengthened from newly emerged to 4 cm. In terms of cell doubling time, although no change took place in the main site of cell proliferation in the cortex‐epidermis, that in the stele shifted basally along the root as the apical meristem expanded.
THE ROLE OF INVAGINATIONS IN ARMED MESOPHYLL CELLS OF PINE NEEDLES
Authors: WIEBE H. H. , AL‐SAADI H. A. 
Published: May 2006

SummaryThe distribution of air in the intercellular spaces of pine (Pinus ponderosa Laws) leaves was studied by sectioning the needles under water to trap the air and examining the sections microscopically. Air was present in the intercellular spaces of the chlorenchyma, including the invaginations of armed parenchyma cells. The air could be removed by vacuum or by sectioning the needles under paraffin oil which infiltrated the spaces. The invaginations are extensions of the leaf air space system and would increase conductivity of CO2 to the chloroplasts which line the invaginations.
COMPETITION FOR POLLINATORS AND EVOLUTION IN CENTAUREA
Authors: LACK ANDREW 
Published: May 2006

Summary Centaurea nigra s.l. forms a very variable complex which has received extensive taxonomic treatment. From analysis of previous work it is shown that populations growing on chalk and limestone in association with C. scabiosa flower later than those in the more typical habitat of neutral and acid grassland. The rayed form of the capitula is dominant in these populations, whereas elsewhere unrayed capitula predominate. From observations on the relative numbers of visiting insects, competition for pollinators with C. scabiosa is proposed as a major selective factor influencing these changes.
MORPHOGENESIS IN SCLEROTIUM‐FORMING FUNGI
Authors: HUMPHERSON‐JONES F. M. , COOKE R. C. 
Published: May 2006

SUMMARYSclerotium production by Sclerotinia sclerotiorum (Lib.) de Bary, Sclerotium rolfsii Sacc. and S. delphinii Welch was enhanced by white light, the most effective wavelengths being in the blue and near‐ultraviolet regions of the spectrum. Sensitivity of dark‐grown cultures to light decreased with age. The effect of light appeared to be through the direct induction of sclerotium initials on undifferentiated hyphae. The relevance of these observations to the general study of sclerotium morphogenesis is discussed.
MORPHOGENESIS IN SCLEROTIUM‐FORMING FUNGI
Authors: HUMPHERSON‐JONES F. M. , COOKE R. C. 
Published: May 2006

SUMMARYTwenty‐six out of thirty‐six monoascospore isolates of Sclerotinia sclerotiorum (Lib.) de Bary, when grown in continuous darkness, produced regular zones of sclerotia. Patterns of zonation were independent of linear growth rate and, although rhythmic behaviour was endogenously determined, rhythms could be altered in detail by varying either glucose concentration or temperatue but not light regime. In some isolates, sclerotium production was accompanied by both generalized and localized changes in the growth rate of the colony margin. The implications of these observations are discussed in the context of nutrient availability and sclerotium morphogenesis.
DEMOGRAPHIC ANALYSIS OF THE GROWTH OF LINUM USITATISSIMUM
Authors: BAZZAZ F. A. , HARPER JOHN L. 
Published: May 2006

SUMMARYTraditional growth analysis techniques have dealt with changes in plant weight and leaf area and have contributed a great deal to the understanding of plant growth. However, they have ignored the fact that the plant may be considered as a population of modules perfectly suited for studies of age structure. Plant growth has many analogies with the growth of a population of organisms. Plant modules (e.g. leaves) have a life cycle–birth, juvenile phase, ‘reproduction’ (i.e. contributing resources to the birth of other leaves and ultimately to flowering and seed set), senescence and death.Plants of Linum usitatissimum were grown in a glasshouse under full and 50% light and at densities of 3.9 and 30/flat. Leaf birth rates were reduced by shading and especially by increased plant density. Light and density also influenced the branching pattern, the intrinsic rate of growth (rm), leaf survivorship, life expectancy (ex), and leaf death rates.Leaf death was strongly influenced by the treatments. Regardless of leaf age, leaf area index, flowering time, density or light intensity, leaf death started when the total biomass of the plants was about 13 g/flat. This biomass apparently exceeded the carrying capacity of the soil medium. Experimentally withholding nutrients, shading the lower parts of the plants, and the removal of flower buds influenced the onset of leaf death but the variable that was most effective, was the withholding of nutrients. Death started in the lower leaves and proceeded upwards regardless of leaf age. The number of seeds per plant was more strongly correlated with the number of leaves than with the total leaf area per plant. This study shows that the application of life‐table and other demographic analyses to leaf birth and death is feasible and permits an interpretation of plant response to environmental factors at a more sophisticated level than is possible from classical growth analysis.