bluuebunny/crossref_metadata_2025_split huggingface dataset:
UPTAKE AND ASSIMILATION OF NITRATE AND AMMONIUM BY AN EVERGREEN FYNBOS SHRUB SPECIESPROTEA REPENSL. (PROTEACEAE)
Authors: STOCK W. D. , LEWIS O. A. M. 
Published: May 2006

SummaryThe uptake and assimilation of15N supplied either as NO3−or NH4+has been studied over a 9‐d period inProtea repens, a member of the Fynbos (South African Mediterranean‐type vegetation) to establish the preferred N source for plant growth and development. Low uptake and assimilation rates were found for both NO3−and NH4+feeding (4.8 and 5.9/μg15N g−1fresh mass d−1, respectively) and total15N absorbed over 9 d was greater in the NH4+‐fed plants than in NO3+‐fed ones. The form of N supplied did not cause significant changes in the total N content of the plants over the feeding period and no alteration in total N distribution patterns was evident, the shoot to root nitrogen ratio being 7:3.Distribution of15N between the soluble N fraction and the bound fraction within root and shoot was similar for both NO3+and NH4+‐fed plants. In both treatments approximately 70 % of the15N was found in the root, mainly in the bound fraction.Protea repensappears to have adapted to the conditions prevalent in the later stages of Fynbos succession, not by showing an absolute requirement for a particular inorganic N form, but by an ability to absorb and assimilate small quantities of both NO3−and NH4+, which satisfy the low N demand of this slow growing, evergreen species.
NITROGEN SOURCES AND ‘A’ VALUES FOR VESICULAR–ARBUSCULAR AND NON‐MYCORRHIZAL SORGHUM GROWN AT THREE RATES OF 15N‐AMMONIUM SULPHATE*†
Authors: AMES R. N. , PORTER LYNN K. , ST. JOHN T. V. , REID C. P. PATRICK 
Published: May 2006

SummaryMycorrhizal and non‐mycorrhizal sorghum [Sorghum bicolor (L.) Moench] plants were grown in soil treated with one of three rates of (15NH4)2SO4, fertilizer. Mycorrhizal plants did not significantly differ from non‐mycorrhizal plants in total plant dry weight, total plant N, or percent utilization of the applied N by the whole plant at any fertilizer rate. However, the atom percent 15N excess in shoots, roots and the whole plant, and percent N derived from fertilizer were significantly higher for non‐mycorrhizal plants at the intermediate level of fertilizer N. The percent N derived from native soil sources, and ‘A’ values were significantly higher for mycorrhizal plants, compared to non‐mycorrhizal plants, at the intermediate but not low or high fertilizer rates. The results suggest that, at the intermediate fertilizer rate, where plants produced the most growth, mycorrhizal sorghum plants derived N from a source that was less available to non‐mycorrhizal plants.
THE RELATIONSHIP BETWEEN CADMIUM UPTAKE AND HEAVY METAL TOLERANCE IN THE LICHEN GENUSPELTIGERA
Authors: BECKETT R. P. , BROWN D. H. 
Published: May 2006

SummaryIntra‐ and extra‐cellular Cd uptake were investigated in members of the lichen genusPeltigerasampled from sites with contrasting metal status.Peltigera membranacea(Ach.) Nyl. from a disused Zn mine, previously shown to be tolerant to Zn‐induced inhibitions of photosynthesis, displayed a reduced rate of Cd uptake into the cell compared withPeltigeraspp. from unpolluted sites, suggesting metal exclusion was a tolerance mechanism. Although some differences in extracellular Cd uptake were found, these appeared to be a reflection of inter‐specific variation rather than environmentally‐induced alterations in Cd‐binding capacity. Exposure to a mixture of Cd and Mg showed that intracellular Cd uptake was less inhibited by Mg when lichens originated from the Zn mine, also implying that mine‐site plants had modified uptake systems. Although intracellular Cd uptake is normally light‐stimulated inPeltigera, lichens from the Zn mine lacked this response, suggesting that algal uptake was reduced more than fungal uptake. Photosynthetically Zn‐tolerantP. hymenina(Ach.) Delise from a disused Pb mine, more moderately polluted than the Zn mine, had intracellular Cd uptake rates comparable to those found in lichens from background localities. In addition, treatment of lichens for 1 week with low concentrations of Zn, previously shown to induce photosynthetic Zn and Cd tolerance, had no effect on intracellular Cd uptake. Tolerance in these instances must have been achieved by some other means. It is suggested that a severe metal stress may be required before metal tolerance by exclusion occurs.
THE EFFECTS OF ELEVATED CO2 ON PLANTS
Authors: GARBUTT K. , BAZZAZ F. A. 
Published: May 2006

SummaryFour populations of Phlox drummondii and one population each of Datura stramonium and Abutilon theophrasti were grown in six growth chambers at 300, 600 and 900 μ l l−1CO2, all other environmental variables remaining constant. Changes in timing and numbers of flowers produced were species‐ and population‐dependent. In general, P. drummondii and D. stramonium flowered earlier under high CO2 while A. theophrasti was not affected. Significant population × CO2 interactions were found for several flower production characters in P. drummondii, indicating differential response to elevated CO2 levels even within a species. In D. stramonium, increased biomass in high CO2 caused significantly larger fruits to be formed, but there was no significant increase in seed number.In A. theophrasti, individual seed weight increased with increasing CO2, but total seed weight per plant remained constant.These results are discussed in relation to their possible implications to plant community structure, and the effects on higher trophic levels (e.g. pollinators and plant predators). Qualitative as well as quantitative changes in plants in response to high CO2 must be studied with care to ensure correct predictions of the effects of the global rise in CO2.
LIGHT AFFECTS THE DEPOSITION OF NO2 TO THE FLACCA MUTANT OF TOMATO WITHOUT AFFECTING THE RATE OF TRANSPIRATION
Authors: MURRAY A. J. S. 
Published: May 2006

SummaryThe flacca mutant of Lycopersicon esculentum Mill., in which stomata remain open in darkness, was used to deomonstrate an effect of light on the inward flux of NO2. This effect was not associated with a change in stomatal conductance. However, a flux was still measurable in the dark and the nature of this is discussed. The normal mechanism of ion transport in leaves is suggested as one factor in the determination of the net flux of NO2 onto this mutant tomato.
SAMPLING STRATEGIES FOR MYCORRHIZAL RESEARCH
Authors: REICH LEE , BARNARD J. 
Published: May 2006

SummaryVariance components were determined for the percentage of mycorrhiza formation in roots of apple trees (Malus) and the numbers of mycorrhizal spores extracted from the soil environment of trees growing in the field. For spore counts and root infection, variability was least from tree to tree. With both of the commonly used methods of rating percentage infection, variability was greatest between samples. For counting soil‐extracted spores, the greatest variation was at the subsample level.
GROWTH OF EXPERIMENTALLY RECONSTRUCTED THALLI OF THE LICHEN PARMELIA CONSPERSA
Authors: ARMSTRONG R. A. 
Published: May 2006

SummaryThe centres of thalli of Parmelia conspersa (Ehrh. ex Ach.) Ach. were removed, the major lobes were separated from each other and from the substratum, and then the lobes were glued back together in their original configuration. The mean radial growth, the pattern of seasonal growth, and the degree of variation in growth between lobes of the reconstructed thalli, were similar to those of control thalli. When lobes were removed from thalli and glued apart from one another, the pattern of seasonal growth and the degree of variation in lobe growth were unaffected, but annual growth rates were reduced compared with lobes reconstructed into a thallus. Glueing the lobes together in a different configuration and constructing thalli in which each lobe came from a different ‘donor’ thallus did not influence the mean radial growth of the lobes or the degree of variation in lobe growth. These results suggest that although major lobes of P. conspersa are influenced by the proximity of their neighbours there is little chemical exchange between them. In addition, some thalli may form as a result of the fusion of lobes or propagules derived from different individuals.
DIFFERENCES BETWEEN SEXES IN FLORAL MORPHOLOGY, NECTAR PRODUCTION AND INSECT VISITS IN A DIOECIOUS SPECIES,SILENE DIOICA
Authors: Kay Q. O. N. , Lack A. J. , Bamber F. C. , Davies C. R. 
Published: May 2006

SummarySilene dioica(L.) Clairv. was studied in several wild populations near Swansea and in an experimental population to determine the extent of differences between the sexes in floral morphology, nectar production, and insect visits to flowers, and the effects of these differences on seed set.Male flowers are larger than female flowers and are borne more densely over a longer period. Male flowers have longer and more frequently white corona scales which may mimic the projecting white styles of female flowers. Male and female flowers were observed to secrete similar quantities of nectar sugar on the first morning of opening, but female flowers secreted more than males subsequently, and the total volumes of nectar secreted by female flowers were considerably greater. Male plants varied more than females in the total quantity of nectar sugar secreted per flower. Nectar concentration was nearly always greater in male flowers than in female flowers.Bumblebees, particularlyBombus hortorum(L.),B. pascuorum(Scop.) andB. terrestris(L.), were the most important visitors to the. flowers ofS. dioicain the study sites, with some honeybees [Apis mellifera(L.)], butterflies (mainly Pieridae) and hoverflies (Syrphidae). Some visitors, including those that were most numerous at some sites, made most or all of their visits illegitimately. In the field in 1980 many visitors were observed to discriminate in favour of male flowers, which were much more numerous than female flowers. In the experimental population in 1981, many visitors discriminated in favour of female flowers, which were more numerous than in the field populations but were still substantially outnumbered by male flowers. Some individual bumblebees showed a change in preferences during the day, disciminating in favour of female flowers only during the afternoon, when the nectar resources available from female flowers were proportionately greater. The total numbers of visits that were observed to female and male flowers in the experimental population corresponded closely with the total quantities of nectar sugar available from each sex. The importance of the different insect visitors and of their discrimination between sexes in pollination is discussed. Seed set did not appear to be reduced by discrimination or insufficiency of pollinator visits in closely spaced plants, but was reduced in plants isolated by distances of 15 m or greater.
POLLEN DIAGRAMS FROM DUBH LOCHAN, NEAR LOCH LOMOND
Authors: Stewart Duncan A. , Walker Agnes , Dickson James H. 
Published: May 2006

SummaryThe main features of the vegetational history revealed by study of two sets of cores from Dubh Lochan, near Loch Lomond are as follows:

There was a brief pioneer phase during the end of the Younger Dryas period after the disappearance of the Loch Lomond glacier. Dwarf shrubs and herbs, including arctic‐alpines and pteridophytes, predominated.
There followed a brief phase of Empetrum and Juniperus in the earliest Flandrian.
Next came the expansion of tree Betula and then Corylus at 9350 years B.P. Together these dominated for up to 3000 years, with the arrival of Ulmus and Quercus and expansion of the latter, towards the end of the period.
There followed a temporary expansion of Pinus and the development of mixed Quercus forest with Alnus before 6000 years B.P. The Ulmus decline at 4900 years B.P. was well marked.
Major differences in the pollen spectra of the two cores in terms of the regional, extra local and local components occur during the last 4000 to 5000 years B.P. A hydroseral succession from open water through a Salix carr to a Myrica carr was noted only from the marginal core.
Though pollen indicative of human disturbance occurs from the Ulmus decline onwards and expands towards the top of the sequences, the area has stayed under Quercus forest with Alnus and Betula, there having been no substantial disforestation until the last 1000 years.
ABSCISIC ACID TRANSPORT AND METABOLISM IN GRAPEVINE (VITIS VINIFERA L.)
Authors: LOVEYS B. R. 
Published: May 2006

SummaryRadioactive abscisic acid (ABA) was applied to leaves of potted grapevines (Vitis vinifera L.). During a 24‐h experimental period, the ABA was extensively metabolized within the leaf to phaseic acid (PA), 4′‐dihydrophaseic acid (DPA) and abscisyl‐β‐D‐glucopyranoside (ABAGE), together with a number of unknown metabolites. ABA was transported out of the leaf to the roots. The major metabolite in roots was DPA and, 24 h after application of ABA to the leaves, only 5% of the radioactivity in the roots was present as ABA. Very little ABAGE was formed by roots. Xylem sap, expressed from canes or collected by root pressure exudation, also contained labelled material, a high proportion of which was unmetabolized ABA.It is suggested that export of ABA from leaves to roots and subsequent transport back to the leaves via the xylem occur naturally in unstressed grapevines and that this forms an integral part of the stomatal control mechanism.
THE RELATION BETWEEN THE BRITISH AND THE EUROPEAN FLORAS
Authors: WALTERS S. M. 
Published: May 2006

SUMMARYThe paper presents a brief and personal history of the main developments in British vascular plant taxonomy and distribution studies in a European setting since the Second World War. It assesses the importance of the‘European view', and considers recent and current work under two main heads: the factual information itself, and the presentation of the facts, especially in the form of dot distribution maps.
NEWFERRY AND THE BOREAL‐ATLANTIC TRANSITION
Authors: SMITH A. G. 
Published: May 2006

SummaryThe establishment and expansion of alder [Alnus glutinosa (L.) Gaertner] in Britain between approx. 8000 and 5000 years ago is discussed in relation to changes of climate and sea‐level, and to human influences.Detailed pollen analyses of Mesolithic layers at Newferry, Co. Antrim are presented. Evidence from this and other sites suggest widespread disturbance of forest cover which, by locally reducing competition, (cf. McVean, 1956) appears to have been one of the factors in the establishment of alder.Estuarine habitats are suggested as having importance in the spread of alder but the onset of climatic wetness was probably not a key factor (as bas often hitherto been supposed) other than in the sense of being permissive.
RELATIONSHIPS BETWEEN TOLERANCE TO HEAVY METALS IN AGROSTIS CAPILLARIS L. (A. TENUIS SIBTH.)
Authors: And M. O. HUMPHREYS , NICHOLLS M. K. 
Published: May 2006

SummaryHeavy‐metal tolerance was investigated in Agrostis capillaris L. (A. tenuis Sibth.) using a standard rooting test on plants originating from a copper‐contaminated site (Parys Mountain) and a lead‐contaminated site (Goginan). Six F1 families obtained by interpopulation hybridization and F2 and backcross generations derived from one of them were screened. Estimates of the genetic and environmental components of phenotypic correlation were obtained in terms of both root length and tolerance index. Results are discussed in relation to problems of interpretation of evidence for multiple‐ or co‐tolerance based on tolerance indices and phenotypic correlations.
POLLEN FLOW IN DIMORPHIC TURNER A SUBULATA (TURNERA CEAE)
Authors: And N. RAMA SWAMY , BAHADUR BIR 
Published: May 2006

Summary Turner a subulata J. E. Smith is heterostylous with pin and thrum flower forms and is self–incompatible but cross‐compatible. Pin and thrum flowers produce the same number of pollen grains. Only 3·07% of the pollen produced participates in the pollination. Pin stigmas receive an average of 425 pollen grains and thrums 327. Stigmas of pin flowers receive more thrum than pin pollen grains. Thus in compatible pollinations, pollen flow from the thrum to the pin form was greater than in the reverse direction.
CARBON FLUXES IN LEAF BLADES OF BARLEY
Authors: FARRAR S. C. , FARRAR J. F. 
Published: May 2006

SummaryGas exchange, mass of carbohydrates, and turnover of carbohydrates, have been followed diurnally in barley leaf blades. Mature second leaf blades store sucrose, which occurs in at least two types of pool which turn over at different rates. Over a light‐dark cycle, photosynthesis, sucrose synthesis and translocation all show appreciable changes in rate but are not obviously related; nor is the rate of translocation a function of the total concentration of sucrose in the leaf. In the dark, starch mobilization starts immediately and that of sucrose increases, maintaining the mean rate of translocation in the dark at 77 % of that in the light. Fructans are turned over but show little diurnal variability in mass.
CARBOHYDRATE ACCUMULATION IN OSMOTICALLY STRESSED CYANOBACTERIA (BLUE‐GREEN ALGAE): INTERACTIONS OF TEMPERATURE AND SALINITY
Authors: WARR S. R. C. , REED R. H. , STEWART W. D. P. 
Published: May 2006

SummaryThe effects of temperature and salinity on the carbohydrate accumulation profiles of a range of unicellular cyanobacteria (blue‐green algae) have been studied. Four isolates of Synechocystis sp. which usually accumulated glucosyl‐glycerol produced a second carbohydrate, sucrose, when grown in a seawater‐based medium at high temperature (35°C). In contrast, three sucrose‐accumulating isolates of Synechococcus, grown over a range of temperatures and salinities, did not produce a second detectable low molecular weight carbohydrate in any experimental treatment. The interaction of temperature and salinity was further examined in Synechocystis PCC 6714. Sucrose production was found to be favoured by high temperature and low salinity. The rate and extent of sucrose accumulation differed in cells grown at 20 and 37 °C reaching an upper asymptote 12 h after upshock at 37 °C and 24 h after upshock at 20 °C followed by a decrease to an approximately constant level after 96 h. This is the first demonstration of the accumulation of sucrose as a second osmotically active carbohydrate in cyanobacteria.
EFFECTS OF SOIL MOISTURE STRESS ON THE WATER RELATIONS AND WATER USE OF GROUNDNUT STANDS
Authors: BLACK C. R. , TANG D.‐Y. , ONG C. K. , SOLON A. , SIMMONDS L. P. 
Published: May 2006

SummaryThe work described here formed part of a detailed study of the effects of temperature and water stress on growth and development in groundnut(Arachis hypogaeaL.). Stands of plants were grown in controlled environment glasshouses at mean air temperatures of 25, 28 and 31 °C. Half of each stand was irrigated whenever soil water potential at 10 cm reached –20 kPa. The other half received no further irrigation after sowing, when the soil profile was at field capacity. The effects on plant water status, stomatal conductance and water use were investigated regularly during the growing season.Leaf water potential (Ψ1), turgor potential (Ψp) and stomatal conductance (g1) were already reduced in unirrigated plants by 29 d after sowing (DAS), when leaf area index (LAI) was still below 0.5; g1was more strongly affected than water status. These differences persisted throughout the season as stress increased, g1was poorly correlated with Ψ1and Ψpand of ten exceeded 2 cm s−1in wilted leaves. LAI was not affected before 40 to 45 DAS but was reduced by 20 to 25 % in unirrigated plants between 60 DAS and final harvest. The decreases in g1and LAI reduced canopy conductance by up to 40 %. The conservative influence of decreased g1in unirrigated plants was negated by increases in leaf‐to‐air vapour pressure difference caused by their higher leaf temperatures. Transpiration rates were therefore similar in both treatments and the lower total water use of the unirrigated stand resulted entirely from its smaller LAI. Unirrigated plants made less vegetative growth but produced more pegs and pods. However, impaired pod‐filling reduced pod yields by around 35 %.
ION CHROMATOGRAPHIC DETERMINATION OF LEVELS OF ANIONS IN PLASTIDS FROM FUMIGATED AND NON‐FUMIGATED BARLEY SEEDLINGS
Authors: WELLBURN A. R. 
Published: May 2006

SummaryA range of aqueous and non‐aqueous methods for chloroplast preparation were tested to establish suitable methodology for routine analysis of plastid anion content using high performance ion chromatography (HPIC). Aqueous methods of plastid isolation failed to provide a satisfactory procedure for analysis of anions (other than chloride) but three different non‐aqueous methods all gave satisfactory and effective procedures.The simplest non‐aqueous method was used to analyse the anions in chloroplasts from 9 d old barley seedlings which had been grown in clean air or fumigated for the last 1 to 3 d of growth with high, but not unrealistic, concentrations (0.28 ppm) of either SO2 or NO2. Amounts of chloride, phosphate, sulphate, sulphite, nitrate and nitrite were detected in plastid preparation from both clean air and polluted seedlings. NO2 fumigation had no effect on chloride, phosphate, sulphate or sulphite content but increased the levels of nitrite and decreased those of nitrate especially on the second day of treatment. Similar atmospheric concentrations of SO2 had no effect on chloride content but increased the levels of phosphate, sulphate and sulphite as well as having a similar influence as NO2 upon nitrate and nitrite content. Again all these effects of SO2 were greatest on the second day of fumigation.
MYCORRHIZAL FUNGI AT EIGHTEEN APPLE ROOTSTOCK PLANTINGS IN THE UNITED STATES
Authors: MILLER DIANE DOUD , DOMOTO PAUL A. , WALKER CHRISTOPHER 
Published: May 2006

SummaryVesicular‐arbuscular mycorrhizas of apple (Malus domestica Borkh.) from 18 sites in the USA were examined. Species of Endogonaceae were identified from soil, and their relative abundance determined from spore extractions. There were no evident patterns in geographic distribution of fungi. A range of three to eight species was found among sites, Glomus being more common in number of species and spores than Gigaspora, Acaulospora, or Sclerocystis. Pot cultures made with soil from some sites yielded species not recovered by sieving. Colonizing ability of all fungi isolated was assessed with apple and sorghum. Colonization potential of soils was determined by dilution techniques with apple as the host. Roots from all sites were endomycorrhizal, but not ectomycorrhizal. Proportion and intensity of colonization were negatively correlated with soil Zn and, at most sites, P levels. Colonization of rootstock clones varied among, but not within sites. Soil colonization potential was highly correlated with degree of root colonization in the field, and there was no evidence that any location lacked adequate inoculum potential for apple.