bluuebunny/crossref_metadata_2025_split huggingface dataset:
THE ROLE OF ELECTRICITY IN PLANT MOVEMENTS
Authors: SIMONS P.J. 
Published: May 2006

SUMMARYA survey has been made of the different types of reversible movements in the plant kingdom (including those of carnivorous traps, leaves, floral parts, root tips, cytoplasmic streaming, cilia and flagella) and it is suggested that many are mediated by changes in electrical potential. Many touch‐sensitive movements in higher plants are regulated by propagating electrical signals (action potentials), which relay excitation from the site of stimulation to the motor organ(s), where collapse of sensitive motor cells is brought about. The resulting change in volume of the motor cells causes movement of the entire motor organ. In some cases additional localized changes in electrical potential (receptor potentials) can be induced by external stimuli, which convert specific characteristics of the stimulus into an electrical analogue before triggering an action potential.The role of electrical activity in other plant movements is more speculative. Action potentials do not arise in light‐ or endogenous rhythm‐regulated movements, but changes in the membrane potential of motor cells concerned with these movements may also help to drive the ionic transport which leads to their turgor‐mediated motion. The significance of electrical activity associated with intracellular movements is less certain, but may become the focus of increasing attention as the regulation of actin‐directed cellular movements is further investigated. Electrical impulses comparable to those in higher plants may, however, regulate ciliar and flagellar activity in the motile gametes and spores of lower plants. Thus, it is clear that electrophysiology is an important aspect of many plant movements, and bears a remarkable similarity to excitation in animal nervous systems.
ISOLATION OF POLYSOMES AND POLY(A)‐CONTAINING RNA FROM CHLORELLA FUSCA VAR. VACUOLATA
Authors: LEONARD J. C. , DUNHAM S.M. , THURSTON C. F. 
Published: May 2006

SUMMARYRibonuclease activity in 120000 g supernatant extracts of Chlorella fusca var. vacuolata showed maximal activity at pH 5 and minimal activity at about pH 7·5 in the range 5 to 8·6. Dithiothreitol, high salt concentration and 100 mM tris significantly inhibited ribonuclease activity although the extent of inhibition was not uniform at all pH values. Heparin, poly‐vinylsulphate and sodium dodecylsulphate were largely ineffective as ribonuclease inhibitors under the same conditions.Polysomes were isolated using the method of Jackson and Larkins (1976) without the addition of heparin but including 10 mM dithiothreitol. Sucrose density gradient centrifugation analysis revealed profiles of polysomes consisting mainly of SOS ribosomes and containing a high proportion of large polysomes when cells were treated with 2·5μgml‐l cycloheximide before harvesting. The yield of polysomal material was about 50 A250 units per 1010C. fusca cells. Total RNA extracted from C. fusca was analyzed by acrylamide gel electrophoresis in 98 % formalide. Cells broken by liquid nitrogen grinding gave RNA preparations which were much less degraded than when the French pressure cell was used for cell disruption. Of three methods tested for isolation and deproteinization of RNA, phenol‐cresol deproteinization of extracts in trisbuffered triisopropylnaphthalene sulphonate/p‐amino salicylate gave the highest yield of RNA and was consistent with the conditions established for minimizing ribonuclease activity. Re‐extraction of the phenol phase was necessary to obtain a high yield particularly of poly(A)‐containing RNA. C. fusca cells growing exponentially in the light gave a greater proportion of poly(A)‐containing RNA than light‐limited cells.Poly(A)‐containing RNA was separated from total RNA and from polysomes on a column of oligo(dT)‐cellulose. This fraction, isolated from total RNA consisted mostly of molecules between 2 × 106 and 0·5 × 106 daltons, but a significant proportion of smaller molecules was present when polysomes were first isolated as the starting material. Poly(A)‐tracts obtained by oligo(dT)‐cellulose chromatography of 14C‐labelled poly(A)‐containing RNA were up to about 450 nucleotides in length with tracts 300 nucleotides long apparently most abundant. When the data were corrected for the increase in radioactivity with tract length and the logarithmic distribution of tract sizes on polyacrylamide gels, smaller tracts were shown to be predominant.
QUANTIFYING VESICULAR‐ARBUSCULAR MYCORRHIZAE: A PROPOSED METHOD TOWARDS STANDARDIZATION *
Authors: BIERMANN BRENDA , LINDERMAN R. G. 
Published: May 2006

SUMMARYA standard method for the quantification of root colonization by vesicular‐arbuscular (VA) mycorrhizal fungi is needed. From the examination of roots from three different host species, the estimation of the percentage of the length of root segments containing V A mycorrhizal fungal structures was found to be more accurate than the determination of the percentage of root segments with VA mycorrhizal fungal structures. It was no more time consuming, and was not influenced by segment size. Examination of a minimum of seven samples, each with 25 randomly selected 0‐5 to 10 cm root segments, was needed for confidence limits to be within 10% of the mean It is proposed that, for the sake of comparability between studies, this procedure be adopted as a standard method.
VARIATION IN THE INFECTION OF SILENE DIOICA (L.) CLAIRV. BY USTILAGO VIOLACEA (PERS.) FUCKEL IN NORTH WEST ENGLAND
Authors: LEE J. A. 
Published: May 2006

SUMMARYThe infection of populations of Silene dioica by Ustilago violacea was studied in four areas of north‐west England. Infection showed wide variation in each area but was not readily related to shade stress from trees or shrubs, nor was percentage infection simply related to shoot density. Infected male shoots predominated early in the season, but later, infection was greater in females. Overall, female plants had a higher percentage of infection than males and, in some populations, over a third of the reproductive capacity was lost. Infection reduced the growth of male plants but produced a large increase in the number of flowers on female plants. The results are discussed in relation to the spread of the disease and to the effects of the fungus on the population dynamics of S. dioica.
SUPPRESSION OF AXILLARY BUDS OF ITS HOST BY PARASITIZING CUSCUTA I. COMPETITION AMONG SINKS AND INDIRECT INHIBITION
Authors: TSIVION Y. 
Published: May 2006

SUMMARYThe drastic inhibition of elongation imposed by parasitizing Cuscuta on the lateral shoots of a decapitated pea plant was studied in order to gain further understanding of the relationship between this parasite and its host. Reduction in host‐bud length was caused by the parasite as well as by a growing, partially shaded, lateral shoot of the host. The results were interpreted as competition between sinks on a common pool of photosynthates produced by the host. In such competition, the less efficient sink is weakened.An influence of the parasite which is not directly related to competition for nutrients is effected through the xylem of the host. This was demonstrated by inhibition of lateral buds by a parasite attached below a girdle that separated the buds from the parasite.
THE PHYTOSOCIOLOGY AND ECOLOGY OF SCRAGH BOG, CO. WESTMEATH
Authors: O'CONNELL MICHAEL 
Published: May 2006

SUMMARYScragh Bog, a mire of some 23 ha, harbours plant communities representative of the more important stages in hydroseral succession. These communities are described, classified and mapped according to Zürich‐Montpellier methodology. Fen communities constitute the major part of the vegetation cover and that dominated by Schoenus nigricans forms the basis of a new subassociation within the Cirsio‐Schoenetum nigricantis Br.‐Bl. et Tx. 1952. Other new syntaxa proposed are the Erico‐Sphagnetum plumulosi, the Carici limosae‐Sphagnetum contort and the Salici‐Betuletum pubescentis pyroletosum. Environmental conditions, as assessed by water table, pH and Kcorr measurements and mineral analyses of surface waters, are considered in relation to the vegetation cover. Mineral analyses were performed on Sphagnum plumulosum and other bryophyte species which are important as initiators of the climax raised bog community. Growth measurements were also performed on 5. plumulosum. The significance of the vegetation cover as well as the factors influencing the future rate of succession are discussed.
THE PAST AND PRESENT VEGETATION OF THE CAENLOCHAN NATIONAL NATURE RESERVE, SCOTLAND II. PALAEOECOLOGICAL INVESTIGATIONS
Authors: HUNTLEY BRIAN 
Published: May 2006

SUMMARYThe existence within the Scottish Highlands of small areas of extreme floristic richness, especially with respect to taxa of northern and montane distribution patterns, is discussed. Possible hypotheses to account for the existence of such areas are considered and the importance of site history is stressed.palaeoecological studies made at two sites within the Caenlochan N.N.R. are described. On the basis of these studies the past flora, vegetation and probable land‐use are reconstructed for the Flandrian (post‐glacial) period. Six chronological units are recognized within this period.The inferred floristic and vegetational history is compared with that for other sites. The conclusion is reached that the present rich flora and diverse vegetation of the Caenlochan N.N.R. represents the joint survival from late‐glacial times of many montane taxa in a locality peculiarly‐suited to their needs and relatively undisturbed by man until the recent past.
FACTORS AFFECTING THE VESICULAR‐ARBUSCULAR INFECTION AND MYCORRHIZAL DEPENDENCY OF THIRTEEN WHEAT CULTIVARS
Authors: AZCÓN R. , OCAMPO J. A. 
Published: May 2006

SUMMARYWheat cultivars inoculated with Glomus mosseae show different degrees of mycorrhizal infection and mycorrhizal dependency. Mycorrhizal dependency was affected by root and root/shoot (R/S) ratio dry wts, but neither mycorrhizal dependency nor mycorrhizal infection levels were directly affected by N, P, K, Ca or Mg concentrations in plant tissues.Absence of mycorrhizal infection in some wheat varieties was associated with lack of sugar exudation from the roots rather than with the sugar content of the roots. VA infection led to a decrease in the reducing and total sugar content of root extracts, and this effect was correlated with the degree of mycorrhizal infection.
CHANGES IN THE LEAVES OF FINGER MILLET DUE TO VA MYCORRHIZAL INFECTION
Authors: KRISHNA K. R. , SURESH H. M. , SYAMSUNDER JOSHI , BAGYARAJ D. J. 
Published: May 2006

SUMMARYAnatomical and histochemical differences in the leaves of non‐mycorrhizal and mycorrhizal Eleusine coracana Gaertn. (finger millet) were studied. Striking increases in the thickness of leaves, size of midrib vein, major vein, minor vein, last vein, motor cells, mesophyll cells and number of plastids were noticed in the leaves of mycorrhizal plants. The leaves of mycorrhizal plants contained higher amounts of insoluble polysaccharides and insoluble proteins. These features are discussed from the view point of the effect of endomycorrhizas on the stimulation of plant growth.
BIOLOGICAL CONTROL OF ROOT‐INFECTING BASIDIOMYCETES BY SPECIES OF BACILLUS AND CLOSTRIDIUM
Authors: TAYLOR J. B. , GUY ESMÉ M. 
Published: May 2006

SUMMARYThe effect of flooding was studied on eight basidiomycete fungi growing on pieces of wood which were buried and flooded for 12 weeks. None of the fungi was re‐isolated from the flooded site, and the cause of the phenomenon was investigated, using a bioassay with Peniophora sacrata as the test fungus. When four Bacillus spp. and three Clostridium spp. from this site were added together to McCartney bottles containing soil and P. sacrata, and then flooded, the fungus was killed, but not when single bacterial species were used. This potential was present in 24 of 32 soils in the southwest Pacific.
VARIABILITY IN SEEDLING PROGENIES AND THE EFFECT OF LIGHT REGIMES DURING SEED PRODUCTION ON INTERSPECIFIC HYBRIDS OF POA
Authors: WILLIAMSON CYNTHIA J. 
Published: May 2006

SUMMARYVariability in seedling characters of 11 families derived from Poa ampla × P. pratensis and P. longifolia × P. pratensis hybrids was examined using univariate and multivariate methods.The determinants from within‐family dispersion matrices based on seedling characters enabled separation of the phenotypically very variable families from the more uniform ones. Comparable results were obtained from visual assessment of intra‐family variability on mature, spaced plants which suggested that it was possible at the seedling state to distinguish between families derived from predominantly amphimictic and predominantly apomictic seed respectively.Ramets from 11 plants lifted from the field were kept in three light regimes and in natural daylight during inflorescence and seed development. Inflorescences, seed and resulting seedling progenies all responded to an increase in length of photoperiod and total daily irradiance. Variability in seedling characters was also affected which indicated that the light regime during embryo sac and seed development may influence the proportion of apomictic seed which matures. There was no consistent trend in this response among the hybrids examined.
Studies ON THE TOLERANCE TO SULPHUR DIOXIDE OF GRASS POPULATIONS IN POLLUTED AREAS
Authors: AYAZLOO M. , BELL J. N. B. 
Published: May 2006

SUMMARY Dactylis glomerata, Festuca rubra, Holcus lanatus, Lolium perenne and Phleum bertolonii were collected from one or more of three sites with differing pollution characteristics in the north of England, and screened for tolerance to both acute and chronic sulphur dioxide injury in comparison with either bred cultivars or individuals of the same species collected from clean areas. Selection for tolerance was detected in all species and at all sites, suggesting that this is widespread in the field.Differential response to chronic injury was manifested as effects on senescence, dry matter production, and/or partition of assimilate between roots and shoots. No correlation was found between the degree of acute and chronic injury at either the intraspecific or interspecific levels, which may indicate independent physiological mechanisms for these. Tolerance may evolve within 17 to 25 years. The significance of the evolution of SO2 tolerance for grasslands at polluted sites is discussed.
BIOCHEMICAL EXPLANATIONS OF MORE THAN ADDITIVE INHIBITORY EFFECTS OF LOW ATMOSPHERIC LEVELS OF SULPHUR DIOXIDE PLUS NITROGEN DIOXIDE UPON PLANTS
Authors: WELLBURN A. R. , HIGGINSON CAROLYN , ROBINSON DEBORAH , WALMSLEY CHRISTINE 
Published: May 2006

SUMMARYThree clones of Lolium perenne L. known to show different sensitivities to SO2 pollution, together with other grasses (Dactylis glomerata L., Phleum pratense L. and Poa pratensis L.), were fumigated with low levels of SO2, NO2 and SO2+ NO2. Ratios of glutamate dehydrogenase activity (GDH) to that of glutamine synthetase (GS) were significantly raised by SO2 (6·8 parts 10‐8 for 11 weeks) or SO2+ NO2 in the SO2‐sensitive cloned cultivar S23 of L. perenne and by SO2+ NO2 in cloned Lolium perenne material which has high resistance to SO2 (S23 Bell resistant). In Lolium derived from Pennine upland (Helmshore clone) GDH/GS ratios were unchanged in the presence of SO2 or SO2+ NO2 but all three clones showed slight elevations in ratios in response to NO2 fumigation alone.Within a week after treatment with NO2, all grasses had significantly higher nitrite reductase activities than similar plants given clean air, SO2 or SO2+ NO2 treatments. The presence of SO2 appeared to destroy the ability of the plant to respond to NO2, and this inhibition of a potential detoxification mechanism of nitrite is believed to be one of the main reasons why the SO2+ NO2 combination exhibits more than additive effects upon the growth of grasses.All three clones of Lolium perenne and also Phleum pratense showed enhanced ATP formation in the presence of low (6·8 parts 10‐8 for 20 weeks) levels of NO2, but reduced cyclic photophos‐phorylation in the presence of either SO2 or SO2+ NO2. At higher levels of shorter duration (25 parts 10‐8 for 11 days), rates of ATP formation, ATP content and energy charge ratios were higher in NO2 fumigated tissue than in controls, but lower in SO2+ NO2 treated tissue, although basic electron transport systems were unaffected. It is believed that the principal effect of the pollutant combination is upon proton gradients within the photosynthetic membranes leading to general deficiency in ATP which is necessary both for growth and the repair of secondary pollutant damage elsewhere.Parts 10‐8 (parts per hundred million) = quantity in μ m‐3× (1/mol. wt × 106) × 0·0224 × 108 at s.t.p. * for 11 weeks) or SO2+ NO2 in the SO2‐sensitive cloned cultivar S23 of L. perenne and by SO2+ NO2 in cloned Lolium perenne material which has high resistance to SO2 (S23 Bell resistant). In Lolium derived from Pennine upland (Helmshore clone) GDH/GS ratios were unchanged in the presence of SO2 or SO2+ NO2 but all three clones showed slight elevations in ratios in response to NO2 fumigation alone.
CONTROL OF DEVELOPMENT IN CHENOPODIUM ALBUM L. BY SHADELIGHT: THE EFFECT OF LIGHT QUANTITY (TOTAL FLUENCE RATE) AND LIGHT QUALITY (RED.FAR‐RED RATIO)
Authors: MORGAN D. C. , SMITH HARRY 
Published: May 2006

SUMMARYIn nature, fluence rate and the red.far‐red ratio are reduced in shadelight beneath vegetation; both show similar exponential decays with increasing canopy density. An assessment of the degree to which each of these factors controls development in natural shade was made by comparing Chenopodium album plants grown under vegetational shade with those grown under the controlled environment light treatments of low fluence rate, and combined low fluence rate and low red: far‐red ratio. The observations of stem extension and specific leaf area from vegetational shade were entirely consistent with the effects of the controlled environment light treatments. The increase of specific leaf area in natural shade was probably due to the low fluence rate; the initial rapid stem extension in natural shade was probably due to the reduced red: far‐red ratio. There is good evidence to suggest that the latter is a phytochrome‐controlled phenomenon.
THE REPRODUCTIVE BIOLOGY OF ASCLEPIAS TUBEROSA
Authors: WYATT ROBERT 
Published: May 2006

SUMMARYIndividual flowers of the self‐incompatible milkweed Asclepias tuberosa are available to pollinators for 7 or 8 days; however, there is a large overlap in flowering time (4 to 5 weeks) within and among inflorescences on a single plant and therefore the possibility of high levels of self‐pollination. Pollinator activity closely follows availability of flowers, although the more rapid decline of the former may indicate switching of pollinators to other plant species flowering simultaneously. These observational data are combined with experimental crossing data to write probability functions for a simple multiplicative model incorporating both extrinsic and intrinsic factors determining fruit‐set. Fruit‐set predictions from the model are very close to the 033% observed in natural populations of A. tuberosa.
MEGASPORES WITH MULTIFURCATE AND BIFURCATE PROCESSES FROM OLD RED SANDSTONE FACIES OF TOURNASIAN AGE, FROM THE TAFF GORGE, SOUTH GLAMORGAN, WALES
Authors: ALLEN K. C. , ROBSON J. 
Published: May 2006

SUMMARYSeven megaspore species referable to the genera Hystricosporites and Ancyrospora are described from rocks of lowest Tournasian age in South Wales. Three species, Hystricosporitespyramidalis, Hystrictosporites proximo‐tuberculatus, and Ancyrospora cambrica are new, and Hystricosporites bedfordi is a recombination. Further information is added to previously described species, particularly on the exinal layers. The problems of separating the two genera are discussed.
NITROGEN ASSIMILATION, ROOT GROWTH AND WHOLE PLANT RESPONSES OF SOYBEAN TO ROOT TEMPERATURE, AND TO CARBON DIOXIDE AND LIGHT IN THE AERIAL ENVIRONMENT *
Authors: Jr RUFTY THOMAS W. , Jr RAPER C. DAVID , JACKSON WILLIAM A. 
Published: May 2006

SUMMARYVegetative soybean plants were exposed to root temperatures of 18, 24, and 30 °C in each of three aerial environments varying in light and CO2. Under high light (700 mUE m‐2 s‐1) at ambient CO2 (400 mUl l‐1) nitrate absorption and root growth were less at 18 and 30°C than 24°C. Both nitrate absorption and root growth were more sensitive to increasing root temperature under low light (325 μE m‐2 s‐1) and less sensitive under enriched CO2 (1000 μl l‐1). As indicated by dry matter accumulation, net flux of photosynthate to the roots was correlated with the changes in aerial environment. It was concluded from these relationships that the variation in root growth and nitrate uptake resulted from altered utilization of carbohydrates in the roots and that altered utilization of carbohydrates with increasing root temperature resulted from disproportionate partitioning of carbohydrate among root functions.Although differences occurred in the amount of nitrogen translocated out of the root, nitrogen accumulation in the shoot was primarily a function of nitrate absorbed. Restrictions in dry matter accumulation in the shoot were similar to restrictions observed in the root. A decrease in emergence of new leaves was often the first response observed, with decreases in leaf area and dry wt occurring later. The integrated plant response to moderate root temperature stress is interpreted as evidence for an interdependent plant system, predominantly regulated by carbohydrate flux to the root and nitrogen flux to the shoot.
THE STRUCTURE OF THE SPORES OF GIGASPORA MARGARITA
Authors: SWARD R. J. 
Published: May 2006

SUMMARYLight and electron microscopy have been used to study the changes that accompany germination in the spores of Gigaspora margarita. Regular germination is achieved following surface sterilization of the spores and the possible role played by sodium hypochlorite in spore activation is discussed. Following spore activation there is considerable redistribution of cytoplasm with a subsequent accumulation of cytoplasmic and wall material in the region of the bulbous‐shaped attachment. Germ‐tube development occurs in this region without the production of peripheral compartments that have been described for other spore types. The possible significance of this feature and the mode of germ‐tube wall development are discussed.
COMPARATIVE WATER RELATIONS AND PHOTOSYNTHESIS OF MYCORRHIZAL AND NON‐MYCORRHIZAL BOUTELOUA GRACILIS H.B.K. LAG EX STEUD.
Authors: ALLEN MICHAEL F. , SMITH WILLIAM K. , Jr MOORE THOMAS S. , CHRISTENSEN MARTHA 
Published: May 2006

SUMMARYThe rangeland grass, Bouteloua gracilis was inoculated with its mycorrhizal symbiont, Glomus fasciculatus, to determine the influence of vesicular‐arbuscular mycorrhizae on water status, stomatal behaviour and photosynthesis as well as gross plant morphology, biomass and phosphorus content. Mycorrhizal infection increased transpiration rates by over 100% with 50 to 70% lower leaf resistances to water vapour diffusion. Leaf xylem pressure was not different between mycorrhizal and non‐mycorrhizal plants indicating that whole‐plant resistance to water transport was reduced by more than 50%. Photosynthetic rates under saturating light conditions increased 68% with infection as a consequence of a 33% reduction in stomatal resistance and a 67% reduction in mesophyll resistance to CO2 uptake. Mycorrhizal infection did not affect biomass or gross plant morphology after 30 weeks of growth, but increased chlorophyll and phosphate concentrations by 28% and 70% respectively. These physiological changes indicate that mycorrhizae may substantially alter survival ability of Bouteloua gracilis.