bluuebunny/crossref_metadata_2025 huggingface dataset:
NITROGENASE AND HYDROGENASE IN CYANOPHILIC LICHENS
Authors: MILLBANK J. W.
Published: May 2006

The 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

Thalli 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

The 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

The 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

Ultrastructural 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

The 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

Previous 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

Bud 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

Growth 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

Reciprocal 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

The 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

Mycorrhizas 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

The 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

The 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

Data 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

The 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

Twenty‐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

Spread 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

Tubules 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

The 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.).
THE INTERDEPENDENCE OF PHOTON IRRADIANCE AND FREE CARBON DIOXIDE OR BICARBONATE CONCENTRATION ON THE PHOTOSYNTHETIC COMPENSATION POINTS OF FRESHWATER PLANTS
Authors: MABERLY S. C.
Published: May 2006

Summary

The free CO2 (CO2*) and HCO3− compensation points of eight freshwater macrophytes and four phytoplankters were measured using a pH‐drift technique developed by Allen and Spence (1981). Below a critical photon irradiance, which was about that at which net photosynthesis was half‐maximal, CO2* and HCO3− compensation points increased with decreasing photon irradiance. However, the CO2* compensation point of two species that were able to use HCO3− were little or not affected by photon irradiance. The light compensation point increased at low CO2* or HCO3− concentrations. The simultaneous generation by phytoplankton of light and carbon depletion could have a large deterimental effect on macrophyte performance.
EFFECTS OF INSECT TRAPPING ON GROWTH AND NUTRIENT CONTENT OF PINGUICULA VULGARIS L. IN RELATION TO THE NUTRIENT CONTENT OF THE SUBSTRATE
Authors: ALDENIUS JOHAN , CARLSSON BENGT , KARLSSON STAFFAN
Published: May 2006

Summary

The significance of the carnivorous habit of Pinguicula vulgaris L. was studied when plants were fed with insects and/or supplied with complete nutrient solution in the substrate. In most cases, plants supplied with insects alone or in combination with fertilizer showed higher values for dry wt, number and length of leaves, and concentrations of nitrogen and phosphorus. The amount of nitrogen absorbed when insects were added to fertilized plants was larger than the insects contained. It is inferred that P. vulgaris uses both nitrogen and phosphorus from the insect. It is hypothetized that some other substance is also obtained from the insects and used for the uptake by roots or utilization of nitrogen. No major differences in response were found between plants from the two sites studied, i.e. one relatively rich and one relatively poor mire in the Torneträsk area, North Sweden.
EFFECT OF DROUGHT STRESS AND VESICULAR–ARBUSCULAR MYCORRHIZA ON CITRUS TRANSPIRATION AND HYDRAULIC CONDUCTIVITY OF ROOTS*
Authors: LEVY YOSEPH , SYVERTSEN J. P. , NEMEC S.
Published: May 2006

Summary

Infection of rough lemon seedlings (Citrusjambhiri Lush) by the vesicular–arbuscular mycorrhizal (VAM) fungus, Glomus intraradices (Schenck and Smith), increased root growth and transpiration rate and reduced leaf water potentials relative to non‐infected control plants. Half of the VAM and control plants were subjected to three drying cycles each of 5 to 7 days. The hydraulic conductivity of previously drought stressed root systems was lower than that of the well‐watered plants and VAM infection further reduced root conductivity. These data suggest that the higher root densities and higher transpiration rates of VAM infected plants may have depleted soil water more quickly than the non‐infected seedlings and resulted in more severe water stress conditions during drought cycles.
ECOLOGICAL ROLES OF BASIDIOMYCETES FORMING DECAY COMMUNITIES IN ATTACHED OAK BRANCHES
Authors: BODDY LYNNE , RAYNER A. D. M.
Published: May 2006

Summary

From sites in south‐west England attached oak (Quercus robur) branches bearing basidiomycete sporophores were cut down from mature trees, and the three‐dimensional structure of their decay communities analysed. Twelve basidiomycetes characterized the decay communities. These fungi varied in their ecology, particularly in relation to their ability to colonize living wood, and their interaction with each other and with animals. Phellinus ferreus, Stereum gausapatum and Vuilleminia comedens were pioneers actively growing in partially living branches and causing extensive white rot but little cambial loosening. Peniophora quercina behaved similarly but was often confined to the ends of branches. Exidia glandulosa appeared principally to cause cambial death and loosening leading to white rot in the wood. Phlebia rufa seemed to act as a pioneer causing white rot but only in obviously weakened branches. Coriolus versicoior and Phlebia radiata were secondary invaders only, readily replacing other fungi. Peniophora lycii and Stereum lursutum were each only obtained once. The roles of Hyphodertna setigerum and Schizopora paradoxa were less clear, but both were closely associated with insect activity.
COMPARATIVE GROWTH OF THE AUSTRALIAN TEMPERATE PASTURE GRASSES: PHALARIS TUBEROSA L., DACTYLIS GLOMERATAL. AND FESTUCA ARUNDINACEA SCHREB
Authors: SAMBO E. Y.
Published: May 2006

Abstract

A study of the factors controlling productivity (dry‐matter production) during early growth was made for the four perennial temperate pasture grasses: Phalaris tuberosa L. cvs. Australian and sirosa (Australian Phalaris and sirosa Phalaris, Festuca arundinacea Schreb. cv. derneter (demeter fescue) and Dactylis glomerata L. cv. currie (currie cocksfoot). A detailed analysis was made of the partitioning of dry matter into the separate leaf and sheath fractions on the main shoot and tillers.

In the period covering early growth (up to 71 days from sowing), a high relative growth rate was associated with a high rate of leaf appearance in currie cocksfoot, enhanced by a high tillering capacity. As a result, currie cocksfoot, although initially the smallest in size, increased its productivity to outyield Australian phalaris and equal that of sirosa phalaris and demeter fescue. The last two cultivars consistently showed higher productivity than Australian phalaris and currie cocksfoot throughout most of early growth. This was attributed to high leaf growth rates resulting in bigger leaf areas. A high leaf extension rate was associated with higher productivity.
LEAF DEMOGRAPHY, FLOWER PRODUCTION AND BIOMASS OF DIPLOID AND TETRAPLOID POPULATIONS OF PHLOX DRUMMONDII HOOK. ON A SOIL MOISTURE GRADIENT
Authors: GARBUTT K. , BAZZAZ F. A.
Published: May 2006

Summary

We investigated the effects of chromosome doubling upon leaf demography, flower production, biomass and response breadth on a soil moisture gradient of three varieties of Phlox drummondii, each variety being represented by two cytotypes.

Increased chromosome number produced slower growth rates, increased leaf and plant longevity, and a tendency to flower later, less synchronously and produce fewer flowers. The loss of the ability to reproduce in hydric environments was also observed in all tetraploids. Other factors such as degree of response breadth, overlap and increased vigour due to increased chromosome number were found to be genotype dependent. Level of polyploidy had no effect upon the number of pre‐reproductive deaths.
MORPHO‐ECOLOGICAL STUDIES OF LOWERING IN THE SEEDLING OF THE GEOPHYTE IXIOLIRION TATARICUM (PALL.) HERB.
Authors: GALIL J.
Published: May 2006

Summary

The structure and behaviour of seedlings of the geophyte Ixiolirion tataricum has been studied. Germination is hypogeal. The cotyledon consists of a haustorium, an elongated stalk and a basal sheath. Germination takes place at or near the soil surface. By a process of ‘lowering’ the plumular bud reaches its appropriate depth in the soil. Lowering occurs in three successive stages: preliminary lowering by downward growth of the basal sheath, followed by growth of the bud carrying first leaf into a tunnel formed within the outer cortex of the primary root. In the second enlargement of the tunnel is the result of growth contraction of the internal core of the root (core = inner cortex + central cylinder), while in the third stage a wide space is formed within the outer cortex by disintegration of parenchyma cells of the inner cortex. The remaining central cylinder is then pushed in front of the advancing first leaf within this root tunnel.
DEVELOPMENT OF INTERCELLULAR CONNECTIONS BETWEEN OPPOSING CELLS IN A GRAFT UNION
Authors: JEFFREE C. E. , YEOMAN M. M.
Published: May 2006

Summary

A morphological and developmental framework is presented for the cellular events leading to graft formation in tomato autografts based on scanning and transmission electron microscopy. Initial adhesion in the pith of grafts is followed by confrontation of new cells generated from the peripheral tissue of stock and scion. Pectinaceous beads on the surfaces of these cells establish a mechanical union between the cell surfaces, forming the functional equivalent of a middle lamella, Plasmodesmata formed de novo at the point of contact between opposing cells link the cell membranes, forming a potential pathway of communication of high specificity. Subsequently, wound vessels differentiate within the ‘callus’ at the graft union, and are connected into the vascular system of stock and scion by wound vessels differentiating from vascular and cortical parenchyma. The significance of these cellular interactions is discussed.
ACID PHOSPHATASE ACTIVITY IN SPHAGNUM SPECIES IN RELATION TO PHOSPHATE NUTRITION
Authors: PRESS M. C. , LEE J. A.
Published: May 2006

Summary

Acid phosphatase activity in 11 Sphagnum species collected from one or more of 13 sites in the U.K. and Sweden was negatively correlated with tissue phosphorus concentration. The effects of phosphate supply on enzyme activity were investigated in both laboratory and field experiments. Phosphate enrichment reduced enzyme activity and phosphate starvation increased enzyme activity. The results are discussed in relation to the use of acid phosphatase as an indicator of phosphate supply in both natural and polluted ecosystems.
LEAF AND FLOWER DEMOGRAPHY OF TRIFOLIUM REPENS L.
Authors: TURKINGTON ROY
Published: May 2006

Summary

Two clones of Trifolium repens L., differentiated in response to their neighbours, the grasses Dactylis glomerata L. and Poa pratensis L., were grown as single ramets in mixture with these same two grasses. At weekly intervals for 59 weeks, births and deaths of leaves and flowers, and extension of stolons were recorded. These birth and death statistics were used to calculate life spans, natality and mortality rates, age class distributions and other demographic parameters of the populations of leaves and Bowers of T. repens L. For both individuals recruitment and death of leaves occurred throughout most of the year. Flowers were produced from early May to mid September by one individual and from late March to mid September by the other. The average life span of leaves does not vary significantly between the four treatments but the timing of birth has a strong influence on the expectation of life. For leaves and flowers from both white clover plants, the population flux was more rapid when growing with P. pratensis L. than with D. glomerata L., yet in both treatments the final population sizes were similar.
NITROGEN METABOLISM IN HALOPHYTES V. THE OCCURRENCE OF MULTIPLE FORMS OF GLUTAMINE SYNTHETASE IN LEAF TISSUE
Authors: McNALLY SHEILA F. , HIREL B. , STEWART G. R.
Published: May 2006

Summary

Ion‐exchange chromatography was used to examine the occurrence of glutamine synthetase (GS) isoforms in leaf tissue of 18 species of coastal plants. Two groups of species were recognizable on the basis of their complement of GS isoforms. One group comprised those species which exhibited two forms of GS, the properties of which were consistent with their being cytoplasmic and chloroplastic isoforms. In the second group were species which had only a single isoform, and exhibited properties similar to those of the chloroplastic isoform. Immunoprecipitation studies with antibody raised to the cytoplasmic isoenzyme of barley were carried out to identify the isoform present in species having only one peak of activity on ion‐exchange chromatography. No relationship was evident between either total GS activity or the occurrence of the cytoplasmic isoform and the photo respiratory capacity of different species.
EFFECT OF GLUCOSE AND ACTIVE CHARCOAL ON IN VITRO SYNTHESIS OF ERICOID MYCORRHIZA WITH VACCINIUM SPP.
Authors: DUCLOS J.L. , FORTIN J. A.
Published: May 2006

Summary

The addition of a small quantity of glucose (0.5 g 1−1) to the culture medium enhanced mycorrhiza formation on Vaccinium angustifolium Ait. and V. corymbosum L. with Pezizella ericae Read in vitro. Under these conditions, 15 isolates of ericoid mycorrhizal fungi obtained from diverse hosts and habitats demonstrated different abilities to colonize the root system of the two species of Vaccinium. Moreover, the addition of activated charcoal especially in presence of glucose or pectin greatly stimulated ericoid mycorrhiza formation by P. ericae on V. angustifolium. The possibility that active charcoal adsorbs toxic compounds from the rhizosphere is discussed.
PURIFIED PHYTOLECTIN FROM THE LICHEN PELTIGERACANINA VAR CANINA WHICH BINDS TO THE PHYCOBIONT CELL WALLS AND ITS USE AS CYTOCHEMICAL MARKER IN SITU
Authors: PETIT PATRICE , LALLEMANT R. , SAVOYE DOMINIQUE
Published: May 2006

Summary

A purified phytolectin was isolated from the nitrogen‐fixing lichen Peltigera canina var canina. This lectin was thermostable, truly non‐specific and may have a molecular weight in its native form of the order of 80000 to 90000. It binds to the appropriate phycobiont cell walls and may be involved in some way in the recognition of, or interactions between, compatible lichen symbionts; it may be used in situ as a cytochemical marker of the free receptor sites in the lichen thalli. We advance a hypothesis that within the lichen the morphological and physiological state of the phycobiont is different in the various parts of the thallus; the capacity of the phycobiont to bind to lectins varies with fluctuations in the symbiotic relationship between partners.
TRANSLOCATION FROM LEAVES OF BARLEY INFECTED WITH BROWN RUST
Authors: OWERA S. A. P. , FARRAR J. F. , WHITBREAD R.
Published: May 2006

Summary

Translocation of14C from first leaves of barley is reduced by rust infection. Infection of the leaf base alone results in enhanced loss of14C from the leaf tip, whilst infected leaf tips show greatly reduced loss. Concentrations of soluble sugar are lower and those of storage polysaccharide higher in rusted leaves. Their amounts and the kinetics of flux of14C through them are used to validate a compartmental model of translocatory carbon flux derived from the pattern of14C‐effiux from the leaf. This model suggests that the major consequences of infection are reduced size of the sucrose transport pool and elimination of a phase of efflux with a half‐life of 2h.
THE STRUCTURE OF THE CUTICLE IN RELATION TO CUTICULAR TRANSPIRATION IN LEAVES OF THE HALOPHYTE SUAEDA MARITIMA (L.) DUM.
Authors: Hajibagheri M. A. , Hall J. L. , Flowers T. J.
Published: May 2006

Summary

Both cuticle and cell wall of the epidermal cells of leaves of Suaeda maritima showed a considerable increase in thickness (Cedeximately 1.8 times) in plants grown in the presence of 0.34 M sodium chloride when compared with plants grown without added sodium chloride. Differences in the structure of the cuticle were also observed. The rate of transpiration in the dark was markedly reduced with increasing concentrations of salt in the external medium. Cuticular transpiration appears to be related to cuticular thickness and to fall with increasing salinity.
ISOPOLLEN MAPS FOR POLAND: 0–11000 YEARS B.P.
Authors: RALSKA‐JASIEWICZOWA MAGDALENA
Published: May 2006

Summary

Isopollen maps were first constructed by Szafer (1935) to illustrate the post‐glacial history of Picea and Fagus in Poland. New more detailed isopollen maps for 1000‐ or 500‐year intervals based on 64 pollen diagrams, many with good radiocarbon‐dating control, are presented for Picea abtes, Ulmus, Corylus avellana, Quercus, Tilia, Alnus, Carpinus betulus, Fagus sylvatica, and Abies alba. These maps illustrate the changing relative importance of these pollen taxa over the last 11000 years and suggest the possible routes of migration of the tree taxa concerned. The complex and diverse migrational history of these major Polish forest trees is demonstrated. The major migration routes appear to have been from the south‐east, south, south‐west and across the middle European lowlands from the west, north‐west and north‐east.
ADAPTATION OF UNICELLULAR ALGAE TO IRRADIANCE: AN ANALYSIS OF STRATEGIES
Authors: RICHARDSON K. , BEARDALL J. , RAVEN J. A.
Published: May 2006

Analysis of data in the literature relating to microalgal adaptations to different photon flux densities indicates that different algal classes have significantly different light requirements for growth and photosynthesis. Although there is some variability within each class, dinoflagellates and blue‐green algae generally photosynthesize and grow best at low photon flux densities. Diatoms also tend to be able to grow at very low photon flux densities (growth for some species has been reported at less than 1 μE m−1 s−2). Comparison of the photon flux densities at which photoinhibition occurs in dainoflagellates and diatoms suggests that the former often experience photoinhibition at comparatively low irradiances. In contrast, diatoms often can tolerate relatively high light environments. This tolerance of a large absolute range of photon flux densities may, in part, explain why diatoms are often associated with spring blooms. Green algae
OSMOREGULATION IN HIGHER PLANTS: EFFECTS OF NaCl SALINITY ON NON‐NODULATED PHASEOLUS AUREUS L. I. GROWTH AND MINERAL CONTENT
Authors: IMAMUL HUQ S. M. , LARHER F.
Published: May 2006

The adaptation, growth and changes in mineral composition of Phaseolus aureus L. were studied at six levels of NaCl, ranging from 10 to 200 mM. Plants tolerated up to 150 mM NaCl in the growth medium although their growth and mineral composition were adversely affected. Accumulation of Na+ in plant tissue increased with increasing NaClext reaching toxic concentrations and inhibited transport of different inorganic ions. K+ constituted only about 10 % of the total mineral content of plants grown in 150 mM NaCl as against 55 % in the controls. The principal balancing anion to counter Na+ accumulation was Cl−. ‘Ion excess’ in the plant is suggested to be the cause of reduced growth. The behaviour of P. aureus under condition of salt stress is discussed.
INCREASED UPTAKE OF BROMIDE AND CHLORIDE BY PLANTS INFECTED WITH VESICULAR‐ARBUSCULAR MYCORRHIZAS
Authors: BUWALDA J. G. , STRIBLEY D. P. , TINKER P. B.
Published: May 2006

Concentrations of bromide in shoot tissue of field‐grown spring wheat and winter barley on sites both with and without methyl bromide fumigation were significantly higher in plants given mycorrhizal inoculum. In a pot experiment with spring wheat under controlled conditions, mycorrhizal inoculation increased bromide and chloride concentrations in plant tissue, but effects on iodide concentrations were small and inconsistent.

A specific ability of mycorrhizal plants for increased uptake of chloride and bromide through mycorrhizal hyphae seems unlikely because both ions are highly mobile in the soil and readily absorbed by roots. An analysis of the cation–anion balance of shoot tissue from a field trial of spring wheat showed that mycorrhizal inoculation increased concentrations of inorganic anions, whilst cation concentrations were little altered. A possible explanation of the increased uptake of halides by mycorrhizal plants may be that the production of organic anions is restricted by the drain of carbon from the host by mycorrhizal fungi.
PHYSIOLOGICAL–ENVIRONMENTAL INTERACTIONS IN LICHENS
Authors: BROWN D. , MACFARLANE J. D. , KERSHAW K. A.
Published: May 2006

The wetting burst, resaturation respiration and basal respiration in Peltigera polydactyla, P. praetextata and Nostoc commune has been examined using both infrared gas analysis and oxygen electrodes. The physical nature of the wetting burst is further confirmed by drying replicates in CO2‐free air, after which the burst is eliminated. The data also shows that resaturation respiration is very dependent on prior events in the field. A prior fast drying rate produces higher resaturation respiration rates than does slow drying. However the length of time a lichen remains fully saturated is largely responsible for the amplitude of resaturation respiration and induces a very evident seasonal component in P. polydactyla. The extent of carbon loss and its potential ecological impact is questioned.
THE INTERACTION BETWEEN CO2 DIFFUSION AND THE DEGREE OF THALLUS HYDRATION IN LICHENS: SOME FURTHER COMMENTS
Authors: COXSON D. S. , BROWN D. , KERSHAW K. A.
Published: May 2006

The pattern of gas exchange in response to changing levels of thallus hydration is presented for several lichen species, together with the effects of high or low CO2 levels on net photosynthesis. The data shows that there is no discernible generalized relationship. Some species achieve very high optimum rates of net photosynthesis at full thallus hydration, while other species have optimum rates at lower levels of thallus hydration with CO2 diffusive resistance either remaining high or decreasing to a minimum coincident with the photosynthetic optimum. Where the diffusive resistance remains high, the phycobiont appears to be continuously CO2 limited even at optimum levels of thallus hydration. There can also be a strong interaction between temperature and the pattern of the CO2 limitation curve due to the high rate of respiration at full thallus moisture and a high thallus temperature. It is concluded that the discrete infra red gas analyser sampling method will slightly underestimate net photosynthetic rates in some species, particularly at full thallus water content, but the same errors will also be equally inherent in flow systems. Accordingly the traditional flow system without the replication advantages of the discrete sampling system, has little to recommend it for comparative seasonal or ecological work. The traditional correlation between the mesic requirements of a lichen and its net photosynthetic response pattern to the degree of thallus hydration is also questioned.
DECOMPOSITION OF SUPPRESSED OAK TREES IN EVEN‐AGED PLANTATIONS
Authors: BODDY LYNNE , THOMPSON WENDY
Published: May 2006

Three oak stands in the Forest of Dean and one in Savernake Forest, planted between 1929 and 1957, were studied (as was a single beech stand in Savernake forest). On the basis of these surveys and other observations, a general pattern of death and decay of the aerial parts of suppressed trees is described. The major agents of decomposition of above ground parts consisted of both basidiomycetes capable of invading living wood and those which act solely saprophytically. Numerous non‐wood‐rotting fungi were also isolated. Most of the basidiomycetes were found to be those which characteristically colonize attached branches on mature oak trees that are not suppressed. These presumably colonize aerially as spores whereas the other basidiomycetes, which were generally found lower down in the trunk, colonized from below ground parts and often produced cords or rhizomorphs growing sub‐cortically.

The consequences of close planting are discussed and a brief comparison is made between beech and oak stands.
DECOMPOSITION OF SUPPRESSED OAK TREES IN EVEN‐AGED PLANTATIONS.
Authors: THOMPSON WENDY , BODDY LYNNE
Published: May 2006

Armillaria (=Armillariella) bulbosa, and several cord‐forming basidiomycetes were found to be the principal colonizers of suppressed oak tree roots on one site studied, whilst A. ostoyae and cord‐forming fungi prevailed on a second site. Interestingly A. mellea was not isolated at all. The rhizornorphic and cord‐forming fungi appeared to colonize peripherally at first but ultimately occupied large volumes of wood. Some cord‐forming fungi were able to replace others in culture whilst in other pairings deadlock was reached. There is some evidence that cord‐forming fungi can replace A. bulbosa and A. ostoyae but cultural experiments were difficult to interpret. A. bulbosa acts mostly saprophytically and probably occupies a similar ecological niche to cord‐forming fungi, e.g. Phanerochaete velutina, Hypholoma fasciculate and Phallus impudicus, which are also saprophytes. Whether A. ostoyae acts pathogenically or purely saprophytically is uncertain. Tricholomopsis platyphylla, another cord‐forming fungus, was prevalent on a third site studied in less detail and is suggested as being a later colonizer than the other cord‐forming and rhizomorphic fungi.

Individual mycelia of A. bulbosa, A. ostoyae and P. velutina are shown to colonize roots in large areas of the sites studied and it is suggested that these fungi may be of significance in nutrient translocation in deciduous woodland ecosystems.