bluuebunny/crossref_metadata_2025_split huggingface dataset:
VARIATIONS IN NITROGENASE ACTIVITY AMONG PURE‐CULTURED FRANKIA STRAINS TESTED ON ACTINORHIZAL PLANTS AS AN INDICATION OF SYMBIOTIC COMPATIBILITY
Authors: DILLON J. T. , BAKER D. 
Published: May 2006

SUMMARY Frankia strains ArI5, AvcIl, AvsI2, CpI1 and MpI1, previously isolated from nodules of actinorhizal plants, were tested in association with various actinorhizal plants to determine differences in nitrogen‐fixing effectiveness. Alnus incana ssp. rugosa, Alnus rubra, Alnus viridis ssp. crispa, Comptonia peregrina and Myrica gale plants, grown in nitrogen‐free water culture, were inoculated with the cultured Frankia strains. Significant differences in rates of acetylene reduction were found among strains which suggested that endophytes were not fully compatible with some or all of the host plants tested. A pattern of compatibilities among hosts and endophytes was developed to explain differences in rates of acetylene reduction.
NITROGENASE AND HYDROGENASE IN CYANOPHILIC LICHENS
Authors: MILLBANK J. W. 
Published: May 2006

SUMMARYThe in vivo evolution of hydrogen by three nitrogen fixing lichens, Peltigera membranacea, Peltigera polydactyla and Lobaria pulmonaria has been studied. The hydrogen evolved concomitant with nitrogen fixation was recycled by means of an uptake hydrogenase and in general the net evolution was zero or small at 5 and 15 °C. At 25 °C there was appreciable net evolution of hydrogen in the Petigera spp. but Lobaria showed no net evolution. Direct comparison of acetylene reduction and nitrogen fixation using 15N2 gave ratios of six and four for Peltigera and Lobaria; these figures imply a significant production of hydrogen and indicate an effective mechanism for countering energy loss under normal in vivo conditions.
THE ASSESSMENT OF NITROGEN FIXATION AND THROUGHPUT BY LICHENS
Authors: MILLBANK J. W. 
Published: May 2006

SUMMARYThalli of Peltigera membranacea, Peltigera polydactyla and Lobaria pulmonaria were labelled with 15N and subjected to simulated episodes of heavy rainfall after periods of drying in a lighted air‐conditioned incubator. Inorganic and total nitrogen was estimated in the eluates. The drying‐wetting cycle was repeated three times. From the level of 15N labelling of the eluates, it was evident that recently fixed nitrogen was released, the inorganic fraction (NH4+) being up to three times more heavily labelled than the organic. The amounts of nitrogen lost in successive episodes generally diminished in logarithmic fashion, the level of labelling remaining approximately constant, implying little or no replenishment of mobile material from insoluble reserves. Up to three times the total nitrogen fixed per day could be lost in one rainfall episode. A preliminary trial showed that nitrogen losses from thalli under less rigorous regimes could be of nutritional benefit to the underlying moss substratum.
15N2 FIXATION AND MOLYBDENUM ENHANCEMENT OF ACETYLENE REDUCTION BY LOBARIA SPP.
Authors: HORSTMANN JUDITH L. , DENISON W. C. , SILVESTER W. B. 
Published: May 2006

SUMMARYThe lichens Lobaria pulmonaria and Lobaria oregana were assayed for 15N2 assimilation in order to confirm previous rates of nitrogenase activity measured by acetylene reduction. In addition, the effect of molybdenum on acetylene reduction activity was studied in both species. The molar conversion ratio (acetylene reduction rate divided by 15N2 fixation rate) was 4.27 for Lobaria pulmonaria and 4.78 for Lobaria oregana. The rate of 15N2 uptake decreased over time in both species. Addition of 1 p.p.m. molybdenum enhanced acetylene reduction by 180% in Lobaria pulmonaria and by 50% in Lobaria oregana. Optimum enhancement in Lobaria oregana was obtained with 1 p.p.m. molybdenum, while 10 p.p.m. may be inhibitory.
TEMPERATURE, LIGHT AND NUTRITIONAL REQUIREMENTS FOR GAMETANGIAL INDUCTION IN THE MOSS BARTRAMIDULA BARTRAMIOIDES
Authors: CHOPRA R. N. , RAHBAR KAVITA 
Published: May 2006

SUMMARYThe optimal conditions of temperature and light for gametangial induction in Bartramidula bartramioides are 25 ± 2 °C and 3500 to 4000 lx of continuous illumination. Presence of sucrose is essential, 1 % being most favourable. Full strength of nutrient solution (Knop's major plus Nitsch's minor) supports best vegetative growth and maximum gametangial formation.
INFLUENCE OF LEAF DIFFERENTIATION ON THE DEVELOPMENTAL PATHWAY OF COLEUS CHLOROPLASTS
Authors: VARKEY P. JACOB , NADAKAVUKAREN MATHEW J. 
Published: May 2006

SUMMARYUltrastructural observations of young Coleus leaves revealed two pathways of chloroplast development within the same leaf. Developing plastids in the mesophyll cells from the basal regions of a leaf contained dense‐staining inclusion bodies associated with newly forming thylakoids while these inclusion bodies were absent from the plastids in the cells of the leaf tip. Studies of the chemical nature of these inclusion bodies suggest that they are made up of proteins and possibly lipids, with no carbohydrates. The material present in the newly‐forming thylakoids is similar in electron density to the inclusion bodies. The difference in chloroplast ontogeny appears to be related to the difference in cell development between the leaf tip and base.
CHLOROPLAST ULTRASTRUCTURE DURING SENESCENCE AND REGREENING OF FLAX COTYLEDONS
Authors: GREENING M. T. , BUTTERFIELD F. J. , HARRIS N. 
Published: May 2006

SUMMARYThe ultrastructural changes in chloroplasts of flax seedling cotyledons were followed during normal senescence. Removal of the growing shoot apex from seedlings with yellowing cotyledons induced a regreening of the cotyledons. The ultrastructure of the plastids was studied to determine whether the regreening was the result of formation of new chloroplasts or a restructuring of the senescing plastids.No evidence of chloroplast de novo synthesis or of chloroplast division was found whereas changes in thylakoid distribution and granal stacking were associated with regreening as was a reduction in osmiophilic plastoglobuli. An increase in plastid peripheral reticulum was found in both normally senescing tissue and in cotyledons of detopped seedlings.
A HISTOCHEMICAL STUDY OF BUD INITIATION IN THE BROWN ALGA SPHACELARIA FURCIGERA*
Authors: BURNS ALAN R. , OLIVEIRA LUIS , BISALPUTRA THANA 
Published: May 2006

SUMMARYPrevious ultrastructural studies of Sphacelaria furcigera have revealed the existence of distinct ‘morphological’ layers within the outer longitudinal cell walls. Bud initiation and development from an axial mother cell involve a change in the layering pattern. The histochemical evidence suggests that the cell wall is composed primarily of alternating layers of sulphated polysaccharides (fucans) and acidic polysaccharides (alignates). Structural integrity of the developing bud cell wall appears to be maintained by a thickened inner alginate layer. The abundance of protein sublayers within the bud cell wall may reflect the presence of enzymes which participate in cell wall loosening and/or synthesis. In addition, a number of the histochemical techniques employed in this study were also applied to the brown alga Fucus distichus for comparative purposes. The results emphasize the need for caution when interpreting histochemical data. Toluidine blue O metachromasia and the periodic acid–Schiff's reaction are evaluated critically and suggestions are given for improving histochemical interpretations.
A MORPHOLOGICAL STUDY OF BUD INITIATION IN THE BROWN ALGA SPHACELARIA FURCIGERA*†
Authors: BURNS ALAN R. , OLIVEIRA LUIS , BISALPUTRA THANA 
Published: May 2006

SUMMARYBud initiation and development in Sphacelaria furcigera involves the de‐differentiation of a quiescent axial cell. This entails loss of cytoplasmic vacuoles and an increase in cytoplasmic mass and density. Cytoplasmic pressure in conjunction with a loosening of the outer longitudinal cell wall contributes to the formation of a bud protrusion. Incorporation of new cell wall material into the outer longitudinal cell wall allows the continued expansion of the bud protrusion. Pre‐mitotic migration of the nucleus to a point midway between the axial mother cell and the protruding bud initial is followed by the reappearance of cytoplasmic vacuoles within the basal portion of the axial mother cell. Karyokinesis soon follows with the formation of two daughter nuclei. The deposition of a cross wall between the two nuclei results in an unequal cell division. The bud cell, typically meristematic in nature, is non‐vacuolated and rich in organelles whereas the sister axial cell is highly vacuolated, poor in organelles and behaves like a quiescent axial cell.
INTERACTION Between A VESICULAR–ARBUSCULAR MYCORRHIZAL FUNGUS AND STREPTOMYCES CINNAMOMEOUS AND THEIR EFFECTS ON FINGER MILLET
Authors: KRISHNA K. R. , BALAKRISHNA A. N. , BAGYARAJF D. J. 
Published: May 2006

SummaryGrowth and phosphorus nutrition of finger millet (Eleusine coracana) on a sterile, phosphorus‐deficient soil was improved by inoculation with either the vesicular‐arbuscular mycorrhizal fungus Glomus fasciculatus or with the streptomycete Streptomyces cinnamomeous. These micro‐organisms interacted antagonistically when added simultaneously or with one 2 weeks after the other: Streptomyces reduced spore production and development of infection by Glomus, while Glomus reduced the multiplication of Streptomyces. Because of this antagonism, dual inoculations stimulated plant growth less than individual inoculations.
EFFECT OF ROOT, SHOOT AND RHIZOBIUM STRAIN ON NITROGEN FIXATION IN FOUR ASIATIC VIGNA SPECIES
Authors: LAWN R. J. , BUSHBY H. V. A. 
Published: May 2006

SUMMARYReciprocal root: shoot grafts of Vigna angularis, Vigna mungo, Vigna radiata and Vigna umbellata were used to study the effects of root and shoot genotype and Rhizobium strain on growth, nodulation and nitrogen uptake of plants grown with nitrogen‐free nutrient solution in sand culture.There were large and significant effects of root genotype, shoot genotype and Rhizobium strain on plant and nodule characters. Interaction effects were invariably small.Effects of both shoot and root genotype on total nodule activity and nitrogen fixation appeared to be due to effects on nodule fresh wt, while those of Rhizobium strain were associated primarily with specific nodule activity. It is suggested that shoot genotype differences in nodule fresh wt arose because of differences in leaf area. Some implications for genetic manipulation of the symbiosis in the Vigna species are discussed.
PHYTOCHROME CONTROL OF SEED GERMINATION IN THE TROPICAL RAIN FOREST PIONEER TREES CECROPIA OBTUSIFOLIA AND PIPER AURITUM AND ITS ECOLOGICAL SIGNIFICANCE
Authors: VÁZQUEZ‐YANES C. , SMITH H. 
Published: May 2006

SUMMARYThe tropical forest pioneer trees Cecropia obtusifolia and Piper auritum germinate and become established in large light gaps of the forest canopy in the rain forest of south‐eastern Mexico. Germination of the seeds of both species is under photocontrol and is triggered when the red: far‐red ratio (R: FR) of the incident light increases due to a reduction of the green canopy density. Exposure to simulated light canopies retarded and reduced germination. The light environment inside the forest inhibits germination totally. Experiments with alternate R and FR light treatments indicate the need for long periods of exposure to R light for germination, and demonstrate a strong reversibility of the R light stimulation by FR light in both species. This property of the seeds may be related to the detection of light gap size and its differentiation from the normal sunflecks of the forest.
FINE STRUCTURE OF MYCORRHIZA FORMED BY CENOCOCCUM GEOPHILUM FR. ON TILIA CORDATA MILL
Authors: PIGOTT C. D. 
Published: May 2006

SUMMARYMycorrhizas formed by Cenococcum geophilum were collected from seedlings of Tilia cordata growing on sandy soil in which the water content was only 2 to 3 % of dry mass (equivalent to water potentials of − 18 to − 55 bars). The fine structure of the mycorrhiza shows that the majority of cells of the fungal mantle, of the bristle‐like extended hyphae and of the root contain living protoplasts with organelles of normal appearance. The mantle and Hartig net are compact tissues (synenchyma) and the outer cells of the mantle and the extended hyphae have thick walls in which the outer electron‐opaque layer has a microfibrillar structure. Hyphal septa in the Hartig net, mantle and extended hyphae are electron‐transparent and have simple pores with Woronin‐bodies. Cells of the root, adjacent to the Hartig net, contain high densities of mitochondria but there is no penetration of intracellular fungal structures (haustoria). There is a well‐defined zone of tannin‐cells.
PHYSIOLOGICAL‐ENVIRONMENTAL INTERACTIONS IN LICHENS
Authors: COXSON D. S. , HARRIS G. P. , KERSHAW K. A. 
Published: May 2006

SUMMARYThe potential for photorespiratory gas exchange has been examined in Nostoc commune which grows as surface colonies in prairie‐grassland, as well as in its lichenized form, Collema furfuraceum. Closed‐loop 14CO2‐12CO2 methods were used together with an examination of CO2 compensation point and the effects of low O2 tension. The results show unequivocally with all methods, that there is no photorespiratory activity in N. commune. Conversely in C. furfuraceum there is a marked inflection in the 14CO2 uptake rate after 3 min in the light; this is followed, on transfer of the lichen to darkness by an immediate and substantial 12CO2 and 14CO2 release which subsequently declines. The interpretation of the latter phenomenon as a classical post‐illumination photorespiratory 14CO2 burst is negated by the total absence of any stimulation of light respiration (LR) at low oxygen tension. A more acceptable interpretation in the strong metabolic channelling of recent photosynthate from the phycobiont. We emphasize the need for several independent measures before the presence of photorespiration (PR) in lichens can be firmly established.
A STUDY OF THE DEVELOPMENT OF RAPHIDE‐FORMING CELLS IN MUSA PARADISIACA USING FLUORESCENCE MICROSCOPY*
Authors: BRUNI ALESSANDRO , DALL'OLIO GIUSEPPE , TOSI BARBARA 
Published: May 2006

SUMMARYThe development of raphide‐forming cells and the differentiation of calcium oxalate needles were investigated in young banana stems using fluorescence microscopy. By employing highly sensitive procedures for the detection of carbohydrates, proteins and RNA, six functional stages in raphide‐cell ontogeny were defined: (1) the appression of cytoplasm to the cell wall in young idioblasts; (2) the synthesis of a polysaccharide matrix with early lacunae; (3) the formation in the lacunae of chambers, the envelope of which contains RNA and protein; (4) the synthesis of glycoproteins and polysaccharides in the chamber envelopes; (5) initiation of the formation of closely packed raphide bundles and the beginning of the crystallization of calcium oxalate and (6) new crystals are formed in a polysaccharide lattice produced in the mucilaginous bundle sheath. The results presented are compared with those of other investigations on the pattern of idioblast development and calcium oxalate deposition in higher plants.
ENVIRONMENTAL HISTORY OF CEFN GWERNFFRWD, NEAR RHANDIRMWYN, MID‐WALES
Authors: CHAMBERS F. M. 
Published: May 2006

SUMMARYData are presented from pollen analytical investigations of an upland basin peat site (GWC) at c. 395 m.o.d. on Cefn Gwernffrwd, mid‐Wales, 15 km north of Llandovery and 15 km southeast of Tregaron Bog. The data are presented in an outline radiocarbon‐dated pollen diagram, covering more than 9500 radiocarbon years and zoned in the conventional manner, and in a detailed pollen diagram covering Atlantic and Sub‐Boreal times, divided into eight phases.The evidence indicates that pine (Pinus) was not a major post‐glacial forest component in this locality, but that hazel (Corylus) may have dominated the upland plateau woods for much of the Boreal. The composition of the Mesolithic forest is discussed and compared with neighbouring areas of the British Isles in the light of this apparent abundance of Corylus and with regard to its migration route into mid‐Wales in the Flandrian.The date for the elm (Ulmus) decline horizon at site GWC is within the expected range and consistent with that obtained from Tregaron Bog.The site is 0.5 km from a recently discovered prehistoric complex of presumed Bronze Age date. Although there is firm evidence for Neolithic clearances, the impact on the forest in this locality was more severe in the Bronze Age. This is apparently at variance with sites elsewhere in mid‐Wales, where an open upland landscape has been claimed since the early Neolithic, and more closely parallels findings in Northern Ireland.
A COMPARISON OF THE PROTEIN AND AMINO ACID COMPOSITION OF OLD AND RECENT BARLEY GRAIN
Authors: SHEWRY P. R. , KIRKMAN M. A. , BURGESS S. R. , FESTENSTEIN G. N. , MIFLIN B. J. 
Published: May 2006

SUMMARYThe amino acid and protein contents of barley grain from archaeological sites dated between approximately 1000 and 3000 years B.C. have been compared with those of grain grown at Rothamsted between 1852 and 1977. The relative amino acid composition of the archaeological samples was remarkably similar to the recent grain, the main differences being decreased relative amounts of lysine and methionine. We were unable, however, to demonstrate the presence of salt‐soluble proteins by electrophoresis or of hordein by electrophoresis or immunoassay. Salt‐soluble protein and hordein fractions extracted from the oldest Rothamsted samples gave less clearly resolved patterns on electrophoresis and isoelectric focusing than fractions from recent grain, indicating some protein degradation. The rate of degradation was apparently faster for ‘C’ hordein than ‘B’ hordein polypeptides.Scanning electron microscopy showed little difference in the relative amounts of large and small starch grains in the different samples. Transmission electron microscopy showed that although the cells of the starchy endosperm of the 1000 B.C. grain were partially disorganized, they did contain structures which resembled the protein bodies present in similar sections of recent grain.
LACK OF MYCORRHIZAL SPECIFICITY BY THE ERICACEOUS HOSTS ARBUTUS MENZIESII AND ARCTOSTAPHYLOS UV A‐URSI
Authors: MOLINA RANDY , TRAPPE JAMES M. 
Published: May 2006

SUMMARYTwenty‐eight cultures of ectomycorrhizal fungi isolated from diverse host and habitat associations were tested in pure culture syntheses with the ericaceous hosts Arbutus menziesii Pursh and Arctostaphylos uva‐ursi (L.) Spreng. All but three of the fungi formed arbutoid mycorrhizas. Sheathing fungal mantles, Hartig net penetration and intracellular colonization were well developed on most mycorrhizas. These results confirm that ectomycorrhizal fungi form arbutoid mycorrhizas and that these particular hosts are broadly receptive towards fungal associates. The significance of these results with respect to ecological and practical implications and better understanding of ectomycorrhizal specificity is emphasized. Arbutoid mycorrhizas are most closely related to ectomycorrhizas than to ericoid mycorrhizas.
PLANT GROWTH RESPONSES TO VESICULAR‐ARBUSCULAR MYCORRHIZA
Authors: MOSSE B. , WARNER A. , CLARKE C. A. 
Published: May 2006

SUMMARYSpread of Glomus caledonius and Glomus mosseae was monitored 3, 15 and 21 months after inoculation in the field. The occurrence of their characteristic spores or sporocarps was used to establish their presence. Thirteen weeks after inoculation, G. caledonius had spread an average of 7.5 cm and a maximum of 22.5 cm from the point of inoculation. After 15 months its spores were irregularly distributed all over the plot irrespective of the initial inoculation points and the fungus had bridged a gap of 4.5 m between inoculation points. After 21 months G. caledonius spores throughout the plot had multiplied about fivefold since the previous survey and many G. mosseae sporocarps were also present. Spores and sporocarp numbers were more similar to those in pot cultures than in normal field situations.Inoculation had residual effects within the plot on the growth of lucerne sown 12 months after inoculation and cut 3 months later.
TUBULAR STRUCTURES IN THE PLASTIDS OF ECHINOMASTUS INTERTEXTUS BRIT. & ROSE (CACTACEAE)
Authors: RIVERA E. R. , ARNOTT H. J. 
Published: May 2006

SUMMARYTubules in hexagonal packing arrays were found in the stroma of proplastids as well as in mature chloroplasts of Echinomastus intertextus Brit. & Rose. The morphology of the proplastids in the shoot meristem was variable. These organelles were found as ovoids, cup shapes and long meandering cylinders. Within the plastids, the tubules were oriented at right angles to the plastidial envelope. Usually, the tubules were contained between the inner membrane of the plastid envelope and a stromal lamella. Sometimes, arrays of tubules alternated with sheets of stromal thylakoids forming several layers of tubules which occupied a large volume of the proplastids. Phytoferritin and lipid droplets were common inclusions of proplastids. Grana were extensive and composed a large portion of the volume of mature chloroplasts. In chloroplasts the tubules were restricted to the periphery, often between the plastid envelope and a sheet of stromal lamella. Frequently, round bulges with tubular components were found at the periphery of the chloroplasts. Starch and lipids were found in chloroplasts.
THE MODERN AND LATE‐QUATERNARY VEGETATION OF THE DOLL CREEK AREA, NORTH YUKON, CANADA
Authors: RITCHIE J. C. 
Published: May 2006

SUMMARYThe modern vegetation of the mountainous Doll Creek region consists of tundra on surfaces above roughly 700 m elevation and spruce woodlands on lower slopes and valleys. Ordination of quadrat cover data by detrended correspondence analysis displays the characteristics and relationships of the vegegation. Tundra on non‐calcareous parent materials is distinctive, dominated by Betula glandulosa, Arctostaphylos alpina, Ledum decumbens and Salix arctica. Limestone ridge surfaces, by contrast, support a tundra dominated by Dryas integrifolia, Carex scirpoidea and Cetraria species; lower slopes on limestone are dominated by a Dryas‐Cassiope‐Tomenthypnum cover which also characterizes the ground vegetation of Picea glauca woodlands on lower surfaces. Bottomland mires are dominated by Picea mariana‐Sphagnum woodlands and moraines support a Picea mariana–Betula glandulosaericad community. Larix laricina shares dominance with Picea glauca at treeline on northwest‐facing gulley surfaces where deep and persistent snow appears to be important.A detailed pollen analysis of one site, using percentage and influx diagrams, running means of influx of the main taxa, and a pollen influx‐vegetation representation calibration method, reveals that immediately following the maximum of the latest glacial cycle (18000 B.P.) the area supported a sparse, unproductive herb tundra on the lower montane slopes and a sedge‐grass marsh complex in poorly drained sites. Between 16000 and 12500 14C years rapid changes in the plant populations occurred, particularly involving species of willow, grass, sedge and herbs. By 12500 the entire area was occupied by a mosaic of treeless communities in response to a slow amelioration of the climate. At 12000 a rapid transition from a warming glacial to a non‐glacial climate stimulated the spread of dwarf shrubs (ericads and birch), increased organic sedimentation, soil humification and paludification, and a gradual increase in spruce until the modern extent and structure of woodland complexes was reached at about 7500 B.P. Slight changes did occur later (6000 B.P.) as alder and tree birch expanded to their modern modest status in the vegetation.The oldest radiocarbon age recorded for these lake sediments is 16000 years, suggesting that, contrary to the original hypothesis, the extensions of Laurentide ice that occupied Doll Creek valley and adjacent areas were part of the latest glacial maximum (18000 to 20000 years B.P.).