bluuebunny/crossref_metadata_2025_split huggingface dataset:
Genecological studies of groundsel (Senecio vulgar is L.)
Authors: THEAKER A. J. , BRIGGS D. 
Published: April 2006

summaryIn order to investigate population variation and its maintenance in groundsel (Senecio vulgaris L.) growing in the Cambridge University Botanic Garden, experiments have been carried out to study heritable differences in the rate of development of progenies of seed‐parents from sites of different history and land use in and round the Garden. There were significant differences between progenies of seed‐parents and between samples from different flowerbeds but the oldest beds did not have the quickest developing plants. Such a pattern of behaviour may be related to the fact that all the beds have been well maintained since the 1950s.Since its establishment, two distinctive genetic variants have entered the Garden. On average, progenies from radiate and from simazine‐resistant seed‐parents in the study area were significantly slower to develop than non‐radiate simazine‐sensitive plants but, in both cases, we also found plants of intermediate rate of development, which might be the result of hybridization between the ‘immigrants’ and the precociously developing non‐radiate, herbicide‐sensitive plants. Progenies from seed‐parents collected at two sites just outside the boundaries of the Botanic Garden were slower in their rate of development than those from the intensively hand‐weeded flowerbeds of the Garden. Samples collected from the same area in different seasons, and grown at the same time, did not differ overall in rate of development, but there were significant differences within flowerbeds.Subsets of progenies of a set of seed‐parents were grown both in summer and winter. The rank order of maturity was not the same in the two parts of the experiment, indicating that the progeny of different seed‐parents have different relative fitness in different times of year. This behaviour, in a species which is capable of reproducing at all seasons of the year, could be a major factor in the maintenance of population variation in the Garden proper.
A pollen diagram, radiocarbon ages and evidence of agriculture on Extwistle Moor, Lancashire
Authors: BARTLEY D. D. , CHAMBERS C. 
Published: April 2006

summaryA pollen diagram is presented from an upland area (about 360 m a.s.l.) on the western slope of the Pennines above Burnley. Radiocarbon assays from the peat suggest that the diagram covers about the last 3000 yr. The recent practice of dating both the ‘humin’ and ‘humic’ fractions of a peat sample leads to problems of assigning dates, especially calibrated dates, to particular events. The evidence from the pollen curves is compared with known climatic, archaeological and historical evidence in an attempt to see whether a chronology based on the humin dates or one based on the ‘weighted mean dates’ is more reliable. The evidence suggests that for this site the humin dates are more realistic and indicate that although the site has been covered by peat from about 1000 BC there were clearance phases in the area in the Iron Age, the Roman Period and from the sixteenth century on.
Fructosyl transferase activity in the tissue‐macerating preparation, pectolyase Y‐23*: physiological role of fructosyl transfer in Aspergillus and significance for studies of fructan synthesis in grasses
Authors: WINTERS ANA. L. , SMEEKENS SJEF C. M. , CAIRNS ANDREW J. 
Published: April 2006

summaryPectolyase Y‐23 is a commercially available plant tissue‐macerating preparation derived from culture filtrates of Aspergillus japonicus. When incubated with 600 mol m−3 sucrose at pH 5.5 and 30 °C, pectolyase catalyzed the rapid synthesis of oligofructans. During a 5 h incubation, 53 % of the original mass of substrate was converted to oligofructan. Thin layer chromatography (TLC) indicated that the predominant products were the trisaccharide isokestose and the tetrasaccharide nystose, though fructans of up to degree of polymerization (DP) 6 were also detected. The synthesis of oligofructan was accompanied by the release of large amounts of free glucose, but free fructose was a minor product of the reaction, indicating a low activity of invertase in the preparation. The fructan products were stable during incubation periods of up to 24 h showing the absence of fructan hydrolase in the pectolyase preparation. The pectolyase fructosyl transferase reaction was similar to reactions catalyzed by enzymes from other Aspergillus spp. In particular, the reaction strongly resembled the industrial synthesis of the commercial sugar product, Neosugar.The substrate concentration kinetics of glucose release from sucrose by pectolyase were determined and the parameters Vmax and Km for fructosyl transfer were calculated as 218 nkat mg−1 of pectolyase and 67 mol m−3 sucrose respectively. The fructosyl transferase was partially purified by quaternary‐amine ion exchange chromatography.Pectolyase Y‐23 has previously been used in the preparation of a fructosyl transferase derived from barley leaf protoplasts. The pectolyase fructosyl transferase exhibited similar properties to those reported for the barley enzyme.
The effect of infection by Erysiphe pisi DC on acid and alkaline invertase activities and aspects of starch biochemistry in leaves of Pisum sativum L.
Authors: STORR TREVOR , HALL J. L. 
Published: April 2006

summaryThe acid and alkaline invertases of mature leaves of Pisum sativum were partially purified and characterized prior to determining the effects of powdery mildew (Erysiphe pisi) infection on their activities. Seven days after inoculation, infection resulted in significant increases in the activities of both acid and alkaline invertases in whole leaves of cv. Onward, but a significant increase in the activity of only alkaline invertase in isolated mesophyll of cv. Argenteum. Activity of α‐glucosidase was determined in leaves and it was concluded that this enzyme could not be responsible for the increased sucrose hydrolase activity observed in host tissues. Seven days after inoculation, infection caused a significant decrease in leaf starch content, a decrease in the activity of ADP‐glucose pyrophosphorylase, and no significant change in the activity of α‐glucan phosphorylase or content of inorganic phosphate. It was proposed that the decreased content of starch is a result of decreased starch synthesis.
Leaf adaptations of some Shorea species to sun and shade
Authors: ASHTON P. M. S. , BERLYN G. P. 
Published: April 2006

summarySeedlings of four species of the genus Shorea section Doona were examined. All co‐exist in the moist evergreen rain forest of southwestern Sri Lanka. Experiments were designed to investigate some physiological and anatomical attributes of leaves under different light conditions. The attributes considered were net photosynthesis, transpiration, stomatal conductivity, blade and cuticle thickness, stomatal frequency, thickness of upper epidermis and palisade mesophyll, and number of palisade layers. Results demonstrate the close association between anatomical adaptation and efficiency in physiological processes. Results also elucidate some of the relationships between distribution patterns of species across the forest topography and their differences in light and drought tolerance. This indicates that an important period determining site specialization of a species occurs during regeneration establishment. These relationships are not as simple or as ecologically noticeable though as for those relationships documented in many previous studies between tree species of markedly different successional stages or taxonomy.
Leaf fracture toughness and sclerophylly: their correlations and ecological implications
Authors: CHOONG M. F. , LUCAS P. W. , ONG J. S. Y. , PEREIRA B. , TAN H. T. W. , TURNER I. M. 
Published: April 2006

summaryThe fracture toughness of sun‐leaves of 42 tropical tree species growing in Singapore was measured along a ‘least tough’ path using an instrumented cutting technique. Punch‐and‐die (penetrometer) tests were also conducted. Intercostal material was analyzed for crude fibre and crude protein (total nitrogen concentration × 6.25) and the ratio of the two, the index of sclerophylly, calculated for each species. Leaf anatomy was examined and specific leaf area was calculated. Thirty‐seven of the species were from three definable plant communities, namely mangroves, trema belukar (secondary forest on undegraded sites) and adinandra belukar (secondary forest on highly degraded soils).There was a highly significant positive correlation between fracture toughness and index of sclerophylly for the 42 species (R2= 0.43, P < 0.001) brought about largely by a high correlation between toughness and crude fibre content. Fracture toughness was not correlated with lamina tissue dorsi‐ventral thickness but high toughness was clearly associated with the presence of sclerenchyma bundle sheaths and sheath extensions. Analysis of the fracture path for 26 leaves of ten mangrove species showed a high correlation between the area fraction occupied by veins and fracture toughness if one species, Avicennia rumphiana, was excluded. The regression equation for the other nine species gave estimates of the fracture toughness of vein tissue and lamina matrix of 6053 and 327 J m−2 respectively. Punch‐and‐die test results only correlated well with the cutting tests when values were divided by lamina thickness.The ratio of protein to fibre in a leaf (the reciprocal of the index of sclerophylly) has been established as a good predictor of leaf palatability and digestibility to generalist chewing folivores. The high correlation between fracture toughness and the index of sclerophylly for a large sample suggests that leaf toughness could be the factor used as a proximate cue for determining food quality in herbivore foraging strategies.
Effects of a short ozone exposure given at different stages in the development of Plantago major L.
Authors: REILING K. , DAVISON A. W. 
Published: April 2006

summaryThis paper reports a comparison of the effects of the same ozone exposure given at different stages of growth on a population of Plantago major L., which is as sensitive to ozone as Bel‐W3 tobacco. Plants were grown from seed for eight weeks in controlled environment chambers and exposed to 70 μl O3 1−1 7 h d−1 for the whole period or for 2‐wk episodes during weeks 1 + 2, 3 + 4, 5 + 6 or 7 + 8. Controls had charcoal filtered air. Effects on leaf, flower, seed and dry matter production, and on relative growth rate of shoot and root are given.At whatever time the ozone was given, it altered relative growth rate, dry matter partitioning and seed output. The experiment supports the view that assessment of the sensitivity of a herbaceous species can be indicated by a short‐term exposure of young plants, even though the nature of the response may change with development.Comparison of the effect of ozone on dry matter partitioning at different stages of growth suggested that at each stage in development, ozone relatively strengthened the currently dominant sink, therefore reducing allocation to subsidiary sinks. As a plant develops, the relative strengths of sources and sinks change so the effects of an ozone episode on allocation will depend upon the timing. It is concluded that the commonly held view that ozone tends to reduce root growth more than shoot may be an over‐simplification. For native plants growing in the field, the timing of episodes in relation to development may be crucial to understanding ozone impact. On the ecosystem level we need knowledge of response and source‐sink relationships at times of the year when episodes occur.
Modern pollen rain studies of the Nile Delta, Egypt
Authors: AYYAD S. M. , MOORE P. D. , ZAHRAN M. A. 
Published: April 2006

summaryModern pollen studies are proving increasingly valuable in the interpretation of fossil pollen assemblages, but relatively little work has been conducted in the arid and semi‐arid parts of the world. In this study, surface samples from a range of vegetation types along the Mediterranean coastal lands of the north of Egypt were collected. The sites were arranged along three representative sea–landward transects at different points along the Nile Delta coast. Samples have been analyzed for their pollen content and the resulting data ordinated using multivariate techniques (detrended correspondence analysis – DECORANA). The groupings that emerge from this analysis are generally closely related to the vegetation from which they were derived, although it proved impossible to separate saline barren areas from salt marsh sites on the basis of their pollen rain.In order to test the results against fossil material, two short profiles of alluvial sediment were excavated from two of the study areas, and the profiles analyzed for pollen. Ordination of the data from these soil sections provided information on the past history of the sites, mainly related to local successional processes in these maritime environments. The results illustrate the potential of surface studies as a basis for environmental reconstruction in the coastal region of the Nile delta.
A reconsideration of fructan biosynthesis in storage roots of Asparagus officinalis L.*
Authors: CAIRNS ANDREW JOHN 
Published: April 2006

summaryTotal soluble neutral carbohydrate (SNC) from storage roots of seven cultivars of Asparagus officinalis L. was analyzed by HPLC and TLC. Fructan accounted for roughly 90% of the total SNC and, of the fructan fraction, 81–98% was of degree of polymerization of five and larger (DP 5). Smaller oligosaccharides and sucrose represented a correspondingly small proportion of the total SNC. This observation differs from the generally accepted view of Asparagus fructan, which emphasizes the presence of small oligofructan in root tissue.On the basis of chromatographic mobility, neokestose and isokestose were identified as the two components of the trisaccharide fraction. Kestose did not accumulate in any of the cultivars studied.A crude enzyme extract of Asparagus roots was prepared using established methods involving dialysis for 5 d. Microbiological analysis of this preparation revealed heavy bacterial contamination. Oligofructan apparently persisted in this protein preparation despite the long period of dialysis. These observations have consequences for the interpretation of previous reports of in vitro fructosyl transferase data for Asparagus root enzymes. The validity of long‐term dialysis in the study of fructan enzymes is questioned.Crude protein extracts of roots were also desalted using a rapid gel‐exclusion method. When incubated with sucrose under conditions similar to established techniques, both invertase and fructosyl transferase activities were detected in this preparation. The trisaccharide products of the fructosyl transferase reaction were identified on TLC as neokestose, isokestose and kestose; the last did not accumulate in vivo. Oligofructans of DP > 3 were also synthesized by this preparation and the pattern of products revealed by TLC was similar to previous reports. These oligofructan products of enzyme reactions were compared directly with the complete range of fructan structures accumulating in the tissue, using TLC. The enzyme products bore little resemblance to the native fructan pattern. Such enzyme activities are of doubtful physiological relevance and may be the result of artifactual or ancillary activities of other enzymes such as invertase.These findings are discussed with respect to previous studies of Asparagus root carbohydrates and serve as a basis for a critical reassessment of the enzymology of fructan biosynthesis both in this and other plant tissues.
Use of nitrogen by the Nostoc—Gunnera tinctoria (Molina) Mirbel symbiosis
Authors: OSBORNE BRUCE A. , CULLEN ANN , JONES PETER W. , CAMPBELL GARRET J. 
Published: April 2006

summaryComparison of Gunnera tinctoria (Molina) Mirbel plants grown in the presence and absence of nitrogen showed that N2 fixed by the cyanobacterium (Nostoc punctiforme L.) can supply all of the requirements for vegetative growth. Estimates of the proportion of tissue occupied by Nostoc indicates that an actively‐fixing cyanobacterial component (the cyanobiont) of somewhat less than 1 % of the total (host + cyanobiont) biomass was sufficient to meet the demands of the host. On the basis of low nitrogen contents and high C: N ratios the cyanobiont was nitrogen‐limited. In situ nitrate assimilation was limited by nitrate uptake and/or transport. Whole plants did not accumulate nitrate and had little capacity to assimilate nitrate, although nitrate reductase activity could be induced in intact leaves or leaf segments supplied directly with aqueous nitrate solutions. The possible significance of these results is discussed. Growth of G. tinctoria on ammonium was depressed at high concentrations and this species may only be able to use low ammonium concentrations. These results indicate that G. tinctoria is almost entirely dependent on N2 fixed by the cyanobacterium to meet its nitrogen demands and has little capacity to use alternative forms of nitrogen.
Restriction of nodulation by the broad host range Rhizobium tropici strain CIAT899 in wild accessions of Phaseolus vulgaris L.
Authors: KIPE‐NOLT J. A. , MONTEALEGRE M. C. M. , TOHME J. 
Published: April 2006

summaryCommon bean (Phaseolus vulgaris L.) is nodulated by a heterogeneous group of Rhizobium strains. In a search for host plant restriction of nodulation by some of these strains, 50 wild and cultivated bean accessions were evaluated for the length of time taken to form effective nodules with three diverse bean strains. As bean genotypes vary substantially for this character, preference or restriction was defined as a relative parameter between the three Rhizobium strains for a given bean genotype. Many of the bean genotypes evaluated showed no preference for particular strains of Rhizobium though Rhizobium strain CIAT8002 was often slowest to nodulate. Amongst the wild and landrace bean accessions, there was a tendency for materials of Mesoamerican origin to form active nodules more rapidly with CIAT632 (a Rhizobium leguminosarum bv. phaseoli strain isolated from Guatemala) than with CIAT899 (a broad host‐range, R. tropici from Colombia). In contrast, in those cases in which some preference was observed, wild and landrace bean genotypes from Peru and Argentina (Andean origin) nodulated more rapidly with Rhizobium strain CIAT899. There were exceptions to this pattern among bred lines. Three wild bean accessions: G10002 from Mexico, G23418 from Costa Rica and G21117 from Colombia showed strong resistance to nodulation with CIAT899. Formation of effective nodules took more than 10 d longer with CIAT899 than with CIAT632. This strain preference was not altered by changing the time of inoculation between 0 and 8 d after sowing. Within an accession, plant to plant variation was observed in the time taken to nodulate with a given strain of Rhizobium. However this variation persisted in the progenies of contrasting individual plants of G21117.
Effects of excess nitrogen and phosphorus starvation on the extramatrical mycelium of ectomycorrhizas of Pinus sylvestris L.
Authors: WALLANDER H. , NYLUND J.‐E. 
Published: April 2006

summaryThe effect of excess nitrogen alone, and in combination with phosphorus and magnesium starvation, on the production of extramatrical mycelium was studied in Scots pine seedlings ectomycorrhizal with Laccaria bicolor (R. Mre.) Orton, Hebeloma crustuliniforme (Bull, ex St‐Amans) Quel. and Suillus bovinus (L. ex Fr.) O. Kuntze. Seedlings were grown in a semi‐hydroponic cultivation system and the ergosterol assay was used to estimate fungal biomass. The mycelial biomass increased rapidly when N was kept low (10–20 mg l−1) and in balance with other nutrients, but no extramatrical mycelium was produced when the N concentration was raised to 200 mg l−1. The growth of the extramatrical mycelium resumed when the excess N treatment was terminated and the seedlings were returned to a low nutrient regime, Laccaria showing more complete resumption of growth than Suillus, while Hebeloma had a low production of extramatrical mycelium in all treatments. Compared with the external mycelium, the amount of fungal tissue on the mycorrhizal roots (mantle and Hartig net) was much less affected by the high N treatment. P starvation increased the production of extramatrical mycelium tenfold, with almost no difference between high and low N nutrient regimes, while Mg starvation had no effect on the fungal biomass. The high N treatment lowered P and particularly Mg concentration of the needles, regardless of the mycorrhizal status of the plant.It is suggested that nitrogen deposition from the atmosphere may damage the function of mycorrhiza even before root tip studies reveal any decline in the symbiotic state. On the other hand, moderate nitrogen fertilization of forest land unaffected by nitrogen pollution is likely to have only passing effects on mycorrhizal development.
Long‐term exposure of Norway spruce,Picea abies(L.) Karst., to ozone in opentop chambers
Authors: WALLIN G. , SKÄRBY L. , SELLDÉN G. 
Published: April 2006

SUMMARYRates of photosynthesis at different photosynthetic photon flux densities (PPFD; 0–1530 μmol m−2s−1) were measured on three shoot age classes of one clone of Norway spruce,Picea abies(L.) Karst. exposed to three different concentrations of ozone for three seasons (1985–7) in open‐top chambers. The treatments were charcoal‐filtered air (CF), non‐filtered air (NF) and non‐filtered air + ozone (NF +). The rate of net photosynthesis was determined using an infrared gas analyzer (IRGA) connected to a small cuvette, equipped with an artificial light source. In 1‐ and 2‐yr‐old shoots the apparent quantum yield decreased with increasing shoot age and ozone concentration, while no effect was found in the current‐year shoots. The decrease could probably partly be attributed to a lower efficiency of light capture due to a lower content of chlorophyll. No effect was observed on the Kok‐effect or on the convexity of the light response curve in any of the treatments or age classes. The significantly higher light compensation point found in current year shoots from the NF+ treatment compared to that of shoots from the CF and NF treatments was suggested to be attributed to an increase in dark respiration. The effect of ozone was larger on photosynthesis at light saturation than on the apparent quantum yield. It is therefore suggested that ozone has a greater influence on the photosynthetic efficiency at high light conditions than at low light conditions.
The physiological importance of accumulation of cyclitols inViscum albumL.*
Authors: RICHTER ANDREAS , POPP MARIANNE 
Published: April 2006

SUMMARYInvestigations ofViscum albumon 16 different host species revealed an endogenous cyclitol pattern with pinitol, 1‐O‐methyl‐muco‐inositol, quebrachitol,chiro‐inositol, an unidentifiedO‐methyl‐inositol and traces of ononitol. Host‐specific cyclitols including bornesitol, quercitol, viburnitol,scyllo‐inositol and the hexitol, sorbitol, were also stored in the mistletoe. The endogenous cyclitols were accumulated to such high concentrations that they made a large contribution to the osmotic potential. It was estimated that 22.6–43 % of mistletoe carbon is derived from the host.