bluuebunny/crossref_metadata_2025_split huggingface dataset:
METAL UPTAKE IN TERRICOLOUS LICHENS
Authors: GOYAL R. , SEAWARD M. R. D. 
Published: May 2006

SummaryThe observed modifications of the morphology and histology of Peltigera canina and Peltigera rufescens in metal‐polluted environments are: reduction in thallial size and rhizinal length, and dense rhizinal growth, profusely‐branched veins and hypertrophy of the medulla. The value of terricolous lichens as bioindicators of metal‐enriched substrata is related to the biologically‐available metal concentrations in the associated soils and the nature of the substratum.
THE EFFECT OF TEMPERATURE ON THE SURVIVAL OF DRY BRYOPHYTES
Authors: HEARNSHAW G. F. , PROCTOR M. C. F. 
Published: May 2006

SummaryLoss of viability by seven species of bryophyte (Anomodon viticulosus, Racomitrium aquaticum, R. lanuginosum, Tortula intermedia, Andreaea rothii, Frullania tamarisci and Porella platyphylla) kept dry at temperatures between 20 and 100 °C was followed by estimating chlorophyll content after a moist recovery period. Behaviour at different temperatures was qualitatively similar, differing in time‐scale. This ranged from a few minutes or less for 50% loss of chlorophyll at 100 °C to weeks or months for the more resistant species at 37 and 20 °C.For most of the species investigated, the logarithms of the half‐viability times gave straight lines when plotted against the reciprocal of absolute temperature, with little variation of slope between species. The relation is similar to that shown by dry seeds and extrapolation suggests half‐viability times of many years for the more desiccation‐tolerant bryophytes at 0 °C or below. The two Racomitrium species showed curvilinear relationships, with notably great tolerance at temperatures in the middle part of the range investigated.
ESTABLISHMENT OF AN EFFECTIVE ENDOMYCORRHIZAL ASSOCIATION ON CASSAVA IN FLOWING SOLUTION CULTURE AND ITS EFFECTS ON PHOSPHORUS NUTRITION
Authors: HOWELER R. H. , ASHER C. J. , EDWARDS D. G. 
Published: May 2006

SummaryEight cassava (Manihot esculenta) cultivars were grown with or without mycorrhizal inoculation in flowing solution cultures containing approximately 0.1, 1, 10 or 100 μM phosphate. Rice (Oryza sativa), maize (Zea mays), cowpea (Vigna unguiculata) and French bean (Phaseolus vulgaris) were included in the experiment for comparative purposes.Cassava required a higher external phosphorus concentration for maximum yield (≥ 10 μM) than the other species (≥ 1 μM) regardless of the inoculation treatments. Roots of inoculated cassava plants were heavily infected with VA endophytes at 0.1 and 1 μM phosphate, but not at 10 or 100 μM. Non‐inoculated cassava plants were free of infection, and no infections were observed in any treatment on the other species.At 1 μM phosphate, infection of cassava roots was associated with large increases in whole plant dry wt, concentration of phosphorous in tops and roots, and total phosphorus uptake. At 0.1 μM phosphate there were also substantial increases in phosphorus concentration in tops and roots but the infected cassava plants were still severely phosphorus deficient and growth was not improved.The results are discussed in relation to the present state of knowledge about the phosphorus nutrition of cassava.
THE ROLE OF EXCHANGEABLE CALCIUM IN SAXICOLOUS CALCICOLE AND CALCIFUGE MOSSES
Authors: BATES J. W. 
Published: May 2006

SummarySpecies of bryophyte restricted to calcareous rocks in the British Isles consistently exhibit concentrations of calcium 16 to 17 times greater than in species found on non‐calcareous rocks. In both groups of plants, this calcium is predominantly in an exchangeable form. Experiments in which the exchange sites were saturated with Ca2+ ions indicate that the calcicoles have Ca2+ exchange capacities three or four times those of the calcifuges. Several possible explanations for this difference are discussed. One hypothesis, that a high affinity for Ca2+ ions corresponds with a high calcium requirement for permeability control, has been tested experimentally. The results, although far from conclusive, suggest that calcicole mosses may require enriched Ca2+ concentrations in their tissues to maintain the integrity of their cell membranes.
CATION COTOLERANCE IN A SALT‐TOLERANT CLONE OF AGROSTIS STOLONIFERA L.
Authors: HODSON M. J. , SMITH M. M. , WAINWRIGHT S. J. , ÖPIK H. 
Published: May 2006

SummaryThe tolerance of clones of Agrostis stolonifera from salt marsh and inland habitats to the chlorides of lithium, sodium, potassium, rubidium, caesium, magnesium and calcium was measured in water culture by a rooting index of tolerance technique. The salt marsh clone was always more tolerant than the inland clone. This was confirmed for LiCl, NaCl and KCl in separate experiments in which dry wt increments were measured. It is suggested that the evolution of tolerance to NaCl in the salt marsh clone has conferred cotolerance to the other alkali metal chlorides, and that the toxicity of LiCl, RbCl and CsCl at least, results from their cations and is not due to chloride ions nor to osmotic stress. Tolerance towards the two alkaline earth chlorides MgCl2 and CaCl2 was also examined. It is suggested that selection for MgCl2 tolerance may have taken place in the salt marsh clone, and that this tolerance has conferred tolerance to CaCl2.
THE INFLUENCE OF A SPRINGTAIL FOLSOMIA CANDIDA (INSECTA, COLLEMBOLA) ON THE MYCORRHIZAL ASSOCIATION OF LEEK ALLIUM PORRUM AND THE VESICULAR‐ARBUSCULAR MYCORRHIZAL ENDOPHYTE GLOMUS FASCICULATUS
Authors: WARNOCK A. J. , FITTER A. H. , USHER M. B. 
Published: May 2006

SummarySeedlings of leek were grown in a factorial experiment to examine the interactions between mycorrhizal infection with Glomus fasciculatus, soil teachings and the Collembola, Folsomia Candida. The growth of leek was increased by mycorrhizal infection and leachings, the latter having a lesser effect, and reduced by F. Candida. There was a strong interaction between the effects of mycorrhizal infection and the presence of F. Candida since infected plants in pots with the Collembola grew little better than uninfected plants. Evidence from root weight ratios, phosphate inflows and the gut contents of the Collembola all suggest that this is due to grazing of the external hyphae of G. fasciculatus, so rendering the infection ineffective.
THE BREEDING SYSTEM IN PRIMULA VERIS L.
Authors: RICHARDS A. J. , IBRAHIM HALIJAH BT. 
Published: May 2006

SummaryModern textbook accounts of within‐morph incompatibility in Primula usually assume that it is total, or nearly so. However, few published accounts can be traced concerning the efficiency of the incompatibility. These suggest that it is total in P. obconica, but rather weak in P. vulgaris, P. veris, P. auricula and P. sinensis.Our work in P. veris suggests that for one population, within‐morph incompatibility is nearly total at normal temperatures. The mechanism of incompatibility varies between the morphs. In within‐pin pollinations, pollen germination is good, and tubes short and broad, being apparently unable to penetrate stigma papillae for physical reasons.In within‐thrum pollinations, pollen germination is poor and the few tubes produced are broad and misshapen. These and the surrounding stigma papillae fluoresce strongly, and similar effects can be produced with pollen‐free water extracts.A tentative model of the control of incompatibility in Primula is based on an enzyme dimer mode of action.
THE POLLINATION ECOLOGY OF ORCHIS GALILAEA (BORNM. ET SCHULZE) SCHLTR. (ORCHIDACEAE)
Authors: BINO R. J. , DAFNI A. , MEEUSE A. D. J. 
Published: May 2006

SummaryThe flower of Orchis galilaea (Bornm. et Schulze) Schltr. does not contain nectar. Only the males of Halictus marginatus are attracted and pollinate the orchid; females visit the flowers of other plant families. We suggest that O. galilaea has evolved a pollination mechanism based on a sexual attraction specific for the males of H. marginatus. This sexual attraction is the result of the strong, musk‐like scent.
TRACHEARY OCCLUSION IN FRONDS OF PTERIDIUM AQUILINUM (L.) KUHN SHOWING APOSPORY
Authors: SHEFFIELD E. , BELL P. R. , LAIRD S. 
Published: May 2006

SummaryThe occlusion of tracheids in aposporous fronds of Pteridium aquilinum attached to parent plants was found to account for the failure of dye to penetrate to the leaf extremities. The agent responsible for this blockage was seen as an electron‐opaque layer covering the walls and areas of overlap between tracheids. The aposporous behaviour of attached leaves is attributed to the discontinuation in supply of some influence from the parent plant which results from the tracheary occlusion observed.
POLLEN ANALYSIS OF AN INTERGLACIAL DEPOSIT AT WEST ANGLE, DYFED, WALES
Authors: STEVENSON A. C. , MOORE P. D. 
Published: May 2006

SummaryA series of clays and muds underlying head deposits, exposed in a cliff section at West Angle, Dyfed, has been subjected to pollen analysis. Four pollen assemblage zones are described, all being dominated by temperate forest taxa, but with Pinus, Picea and Abies all present in some quantity. Forest disturbances are evident within the profile, in which light‐demanding taxa such as Fraxinus, Juniperus and Corylus become more frequent, as do many herbaceous types. Possible causes of these disturbances are considered, the most likely being local flood catastrophes. It is not possible fully to correlate the pollen sequence with other British and Irish interglacials, but certain features compare closely to some Hoxnian diagrams of eastern England. These are: (i) the presence of Abies, (ii) the occurrence of Picea through the entire profile, (iii) the consistent presence of Tilia in the middle two zones and (iv) the lack of Carpinus maximum.
MID‐FLANDRIAN FOREST HISTORY OF ROUDSEA WOOD NATIONAL NATURE RESERVE, CUMBRIA
Authors: BIRKS H. J. B. 
Published: May 2006

SummaryA pollen‐stratigraphic record from a small (25 m diameter) hollow situated within the Carboniferous limestone area of Roudsea Wood is presented. The record extends from 6680 to 5150 years B.P. and shows that the canopy of the mid‐Flandrian forest around the hollow contained 10 to 30%Quercus, 5 to 15%Betula, 2 to 15%Ulmus cf. U. glabra, 5 to 25%Tilia cordata, 5 to 25%Fraxinus excelsior, 15 to 20%Alnus glutinosa, and 10 to 30%Corylus avellana. Minor trees and shrubs were also present, including Acer campestre, Euonymus europaeus, Rhamnus catharticus, Sorbus torminalis, and Thelycrania sanguinea, all of which grow today at or near their northern British limits near Roudsea Wood.
PHOTOMORPHOGENESIS IN IMPATIENS PARVIFLORA AND OTHER PLANT SPECIES UNDER SIMULATED NATURAL CANOPY RADIATIONS
Authors: WHITELAM G. C. , JOHNSON C. B. 
Published: May 2006

SummaryNitrate reductase activity in the leaves of Sinapis alba L. and Chenopodium album L. was found to be related to the photoequilibrium of phytochrome established under simulated natural canopy radiation (fluorescent white light with added far‐red light) of a relatively high photon fluence rate. Under simulated canopy radiation of low photon fluence rate, more characteristic of ‘shade’ light, the degree of responsiveness of S. alba nitrate reductase has been seen to be reduced. However, in the leaves of Impatiens parviflora L., a species frequently occurring in dense canopy shade, nitrate reductase activity showed a rapid and marked response to changes in phytochrome photoequilibrium with the low‐fluence rate sources. Under these same conditions the elongation growth of I. parviflora internodes also showed a marked and rapid response to changes in the phytochrome system, rather than displaying a reduced response as has been proposed for shade tolerating species.
THE EFFECT OF A MUTATION CAUSING ALCOHOL DEHYDROGENASE DEFICIENCY ON FLOODING TOLERANCE IN BARLEY
Authors: HARBERD N. P. , EDWARDS K. J. R. 
Published: May 2006

Summary Adh1‐M9 mutant barley plants lack a functional ADH1 gene product. The effect of this deficiency in alcohol dehydrogenase (ADH) activity on flooding tolerance is investigated by comparing the behaviour of mutant and wild‐type plants in flooded conditions. It is concluded that there is a specific requirement for a functional ADH1 polypeptide in the immersed seed but not at later stages of development. The significance of these findings is discussed with respect to current theories of flooding tolerance.
INTERACTION OF PHOTOPERIOD AND VESICULAR‐ARBUSCULAR MYCORRHIZAE ON GROWTH AND METABOLISM OF SWEET ORANGE
Authors: JOHNSON C. R. , MENGE J. A. , SCHWAB S. , TING I. P. 
Published: May 2006

SummaryVesicular‐arbuscular (VA) mycorrhizal infection and growth of Citrus sinensis were increased by longer photoperiods. Photosynthesis and stomatal conductances were greater for mycorrhizal plants, but were unaffected by daylength. Phosphorus levels in leaf tissue from mycorrhizal plants were threefold greater than those in non‐mycorrhizal plants and P levels were slightly greater in plants grown under long‐day photoperiods. Root exudation of reducing sugars was greatest for non‐mycorrhizal plants grown under long day photoperiods, but exudation of amino acids was variable. The results suggested that plants grown under long‐day photoperiods have greater basipetal transport of photosynthates resulting in improved mycorrhizal infection and plant growth response.
EFFECT OF FLOWER BUD DEVELOPMENT IN CHRYSANTHEMUM ON VESICULAR‐ARBUSCULAR MYCORRHIZA FORMATION
Authors: JOHNSON C. R. , GRAHAM J. H. , LEONARD R. T. , MENGE J. A. 
Published: May 2006

SummaryRoots of single stem Chrysanthemum morifolium plants were inoculated with the vesicular‐arbuscular mycorrhizal (VAM) fungus, Glomus fasciculatus, at several stages of flower bud development. Compared to vegetative control plants, VAM formation was reduced during early stages of flower bud development, but not during later bud expansion. A decrease of reducing sugars and amino acids in root extracts during early bud development coincided with a decrease in root exudation of these compounds. These results suggest that reduction of VAM formation during early flower bud development resulted from a decrease in the availability and net leakage of metabolites necessary to sustain the mycorrhizal fungus during pre‐ and post‐infection.
PHYSIOLOGICAL‐ENVIRONMENTAL INTERACTIONS IN LICHENS
Authors: KERSHAW K. A. , MACFARLANE J. D. 
Published: May 2006

SummaryThe seasonal response matrix of gas exchange and nitrogenase activity in Collema furfuraceum is presented for a number of factorial combinations of light, thallus temperature (5, 15, 25 and 30 to 35 °C) and thallus water content, throughout the year. The results indicate C. furfuraceum is adapted both to the relatively xeric environment of its cortieolous habitat as well as to the low temperatures experienced in its low‐arctic environment. Of particular interest is the absence of a summer thermal stress response, which eliminates or severely reduces nitrogenase activity during the summer months in some lichens growing in more southerly localities. Equally, ambient temperatures during the winter, which can drop to minus 41 °C, do not affect nitrogenase activity and confirm the resistance of the nitrogenase enzymes in the intact thallus, to low temperatures.There is a remarkable degree of uniformity in the net photosynthetic response matrix, at most light levels, at all experimental temperatures and at all times of the year. The total absence of seasonal photosynthetic acclimation as well as the seasonal constancy of photosynthetic capacity is discussed in terms of differential strategies in contrasting environments.
LIFE HISTORIES AND DEMOGRAPHY OF SHADE‐TOLERANT TEMPERATE FOREST HERBS: A REVIEW
Authors: BIERZYCHUDEK PAULETTE 
Published: May 2006

SummaryInformation is reviewed on the life histories and demographic patterns of shade‐tolerant herbs of temperate deciduous forest. Most of the species that have been studied are deciduous perennials. These species generally have a juvenile (non‐flowering) period of several years followed by an extended period of flower and seed production. About half the species reviewed are self‐incompatible, the others are at least partially self‐compatible. Although vegetative reproduction is common, replacement does not always occur by vegetative spread; many species appear to be able to replace themselves by seed. Sexual reproductive effort ranges from 1–5 to 50 % among the species reviewed; seed weight averages 2–6 mg. Short dormancy periods (one season) are most common, with germination rates generally below 50%.Mortality rates of small plants are high, but decline as plant size increases. ‘Ageing’ does not appear to occur. No information exists on population growth rates of temperate deciduous forest herbs, or on the temporal stability of their population sizes or structures. The transition matrix model is suggested as a promising approach to future studies in plant demography.
PLANT‐INDUCED CHANGES IN THE RHIZOSPHERE OF RAPE (BRASSICA NAPUS VAR. EMERALD) SEEDLINGS
Authors: HEDLEY M. J. , NYE P. H. , WHITE R. E. 
Published: May 2006

SUMMARYChanges in the rhizosphere pH of rape plants (Brassica napus var. Emerald), grown at high root densities (> 90 cm cm−3) in a soil of low P status, were not associated with any detectable increase in the amount of extractable organic acids or their anions, or in the total amount of uronic acids in the soil. Microbial numbers in the rhizosphere soil and unplanted control soil were estimated by dilution plate counting, using an hydroxyapatite (HA) agar substrate, and those colonies capable of producing acid or of dissolving HA were identified. Neither the total number of colonies nor the number of acid‐producing colonies and P solubilizing colonies bore any obvious relationship to the pH of the soil from which they were isolated. However, analysis of the major cation and anion concentrations in the plant tissue showed that more cations than anions were taken up by the rape plants during the period when the rhizosphere pH decreased. The milliequivalents of H+ or OH− required to produce the observed pH changes were calculated from the soil's pH buffer curve and found to agree closely with the difference between the milliequivalents of cations and anions taken up by the plant. A steady decline in NO3− uptake and a small increase in Ca2+ uptake created the cation‐anion imbalance during the period of decreasing rhizosphere pH. H+ release from the roots must have occurred to maintain the charge balance across the root‐soil interface and was the most likely cause of decrease in rhizosphere pH.
CYTOKININ PRODUCTION BY ECTOMYCORRHIZAL FUNGI
Authors: NG P. P. , COLE A. L. J. , JAMESON P. E. , MCWHA J. A. 
Published: May 2006

SUMMARYThe mycorrhizal fungi Rhizopogon luteolus Fr. and Nordh, Boletus elegans Schum. ex. Fr. and Suillus tuteus L. ex Fr., were investigated for cytokinin production in vitro. Culture filtrates in which the fungi had been growing for at least 2 weeks showed cytokinin activity when purified and bioassayed using soybean callus tissues. The cytokinin activity in the culture filtrate increased with longer periods of incubation. A potent inhibitor of callus growth from Boletus elegans culture filtrate which masks cytokinin activity is discussed.
STRUCTURE AND PHYSIOLOGY OF ECTOMYCORRHIZAE
Authors: NYLUND JAN‐ERIK , UNESTAM TORGNY 
Published: May 2006

SUMMARYThe process of mycorrhiza formation in previously uninfected roots was studied in vitro, using the fungus Piloderma croceum Erikss. & Hjortst, and the Norway spruce, Picea abies (L.) Karst, as model organisms. The process could be divided into the following phases: fungal growth stimulation by root metabolites; formation of a hyphal envelope on the root; intercellular penetration by single hyphae, change in fungal morphology into labyrinthic tissue formation leading to Hartig net formation, and extension of labyrinthic tissue to form a mantle. P. croceum, growing in dead tissue, showed saprophytic growth in vitro, a capacity suppressed in living tissue. The way of fungal penetration appeared to be mechanical. A hypothetical model for host‐fungus interactions regulating the mycorrhiza infection process is also discussed.
THE ENZYMES OF POLYPHOSPHATE METABOLISM IN VESICULAR‐ARBUSCULAR MYCORRHIZAS
Authors: CAPACCIO L. C. M. , CALLOW J. A. 
Published: May 2006

SUMMARYThe presence and distribution of enzymes of polyphosphate (polyP) synthesis and degrActation was examined in mycorrhizal and non‐mycorrhizal onion roots, and both external and internal hyphae of the endophyte, Glomus mosseae. PolyP kinase activity was detected in extracts of external hyphae and mycorrhizal roots. Activity was dependent on exogenous polyP and Mg2+, the reaction product being a long chain polyP. Exopolyphosphatase activity was detected in both mycorrhizal and non‐mycorrhizal roots but activity was 134°O greater in the former. Endopolyphosphatase activity was also greater in mycorrhizal roots. Polyphosphatases were detected in extracts of internal hyphae, but not external hyphae. Polyphosphate glucokinase activity was demonstrated in extracts of external hyphae and mycorrhizal roots, the immediate reaction product being glucose‐6‐phosphate. These results are discussed in relation to potential mechanisms of P translocation and transfer in vesicular‐arbuscular (VA) mycorrhizas. A novel technique for isolating the internal hyphae and associated vesicles and arbuscules from mycorrhizal onion roots is described.
ORIGIN AND EARLY GROWTH OF CELERY EMBRYOIDS
Authors: DUNSTAN D. I. , SHORT K. C. , MERRICK M. A. , COLLIN H. A. 
Published: May 2006

SUMMARYSuspension cultures of celery embryoids were initiated by transferring portions of differentiating callus to liquid medium. Light microscope studies of the cells and embryogenic aggregates in the suspensions suggested that the embryoids arose from either single cells within the embryogenic aggregates, when the developing embryoid remained attached to the clump until the globular stage, or from free floating small groups of cells. Both types of development showed the celery embryoids to be of single cell origin. When the embryoid suspension was filtered to remove the larger embryoids and the small embryogenic aggregates and free floating embryoids were mixed with agar and plated, the development of the embryoids depended on the initial inoculum density. At low density further embryoid development was delayed while at the high inoculum density the embryoids became green and grew rapidly into torpedo embryoids with cotyledon leaves and roots. At this stage they could be transferred to a simple inorganic medium to develop into plantlets. The effect of inoculum density was thought to be due to a conditioning effect of the environment. It is suggested that the differentiating units in the embryoid suspension could be used in a cell selection procedure.
THE GROWTH FRACTION OF THE QUIESCENT CENTRE
Authors: CLOWES F. A. L. 
Published: May 2006

SUMMARYEvidence used to support a view that the quiescent centre of roots of Avena sativa, unlike those of other species, has a growth fraction of unity, i.e. all its cells are cycling, has been examined in the light of further investigations. Measurement of potential cell‐doubling times before and during a period of DNA labelling by tritiated thymidine in the quiescent centre and in the surrounding meristem show that there is no reason to reject the notion that many cells of the quiescent centre are out of cycle. Observations on planes of division in the proximal tier of the root cap, which were also used to support belief in a fundamental difference in cell kinetics between Avena and other species are also interpreted differently as a result of additional work.