bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on infraspecific variation in Cyperus longus L. from Europe
Authors: COLLINS ROSEMARY P. , McNALLY SHEILA F. , SIMPSON D. A. , JONES M. B. 
Published: April 2006

SUMMARYClonal material of the temperate C4 species Cyperus longus L. (Cyperaceae) sampled from Cornwall, S. W. Great Britain and Mt Pilion, central Greece was grown under the same environmental conditions. Comparisons were made of the pattern of leaf growth, net photosynthesis (Pn) and the characteristics of the isoenzymes of glutamine synthetase (GS). In addition, we studied the morphological characteristics of these clones and 95 herbarium specimens collected from a range of localities throughout Europe.Principal‐components analysis of the morphological characteristics suggested that European material falls into two distinct morphological groups, typical C. longus and ssp. badius (Desf.) Murb. The clonal material from Cornwall corresponded morphologically with ssp. longus and that from Mt Pilion with ssp. badius. Physiological and biochemical measurements of the two clones indicated distinct differences in the phenology, Pn and stomatal conductance at high light levels, their complements of GS1 and GS2 isoforms and associated temperature stability. It appears, therefore, that ssp. badius represents a distinct ecotype of ssp. longus. However, the apparent taxonomic distinction between the groups requires further investigation of population variation, as our studies were performed on a limited amount of clonal material.
The effects of root cooling and excision treatments on the growth of primary leaves of Phaseolus vulgar is L.
Authors: SMITH P. G. , DALE J. E. 
Published: April 2006

SUMMARYSeedlings of Phaseolus vulgaris L. were grown in nutrient solution at two temperatures and the free abscisic acid (ABA) content of primary leaves measured by radioimmunoassay with a monoclonal antibody (MAC‐62). Transfer of 7‐day‐old seedlings from solutions at 22.5 °C to 10 °C doubled the ABA content per g fresh weight after 6 h and led to a S‐fold increase by 24 h. Shorter incubations led to a 2.5‐fold rise 2 h after the start of cooling. Root‐cooling restricted leaf expansion rate but both the inhibition of leaf growth and the rise in ABA content were reversed when root temperature was returned to 22.5 °C. 2 h after transfer to control conditions half of the extra free ABA induced per leaf by root‐cooling was no longer present. Excision of seedling lateral roots impeded leaf expansion and led to enhanced ABA content after 24 h. Petiole ringing experiments showed that the rapid rise in ABA was not due to blockage of export from the leaves of root‐cooled plants, although export may have contributed to the fall in ABA when cooled seedlings were returned to 22.5 °C.
Ozone accelerates structural degradation of epicuticular wax on Norway spruce needles
Authors: BARNES J. D. , DAVISON A. W. , BOOTH T. A. 
Published: April 2006

SUMMARYScanning electron microscopy was used to investigate the effects of O., fumigation (70 d of 240 μg O3m−3for 6 h d−1during a 12 h photoperiod) on the condition of the epicuticular wax that fills and surrounds the stomatal antechamber of the needles of seven clones of Norway spruce(Picea abies(L.) Karst.). The rate of change of the physical structure of the wax differed between clones, but in all eases O., accelerated the process on current and previous year's needles. The change consisted of a transition from a crystalline array of fine tubes to an amorphous, ‘melted’ layer with no visible structure. This resulted in a higher frequency of stomata occluded by an apparently continuous plug. In four clones, O3, fumigation resulted in 70–80 %, of the stomata on previous year's needles being occluded, in contrast to 7–28 % in charcoal‐filtered air. Five of the clones showed a greater effect of O3, on the wax of the previous year's needles than on current needles. The physiological consequences of such O.,‐induced effects are discussed. Premature wax degradation induced by O3, and/or acid mist may have contributed to the decline of spruce in high‐altitude forests of continental Europe.
Regulation of gene expression in ectomycorrhizas
Authors: HILBERT J. L. , MARTIN F. 
Published: April 2006

SUMMARYIn an effort to investigate the presence of any ‘symbiosis‐specific’ genes that are expressed specifically during the development of ectomycorrhizas, the polypeptide content of Eucalyptus‐Pisolithus mycorrhizas, uninfected Eucalyptus globulus (Maid et al.) Kirkp. short roots, and free‐living Pisolithus tinctorius Coker & Couch mycelia have been compared. Analysis of the soluble proteins by two dimensional polyacrylamide gel electrophoresis showed that most of the polypeptides observed in mycorrhizas were already synthesized in free‐living mycelia. The effects of mycorrhizal infection on polypeptide accumulation fell into three distinct categories: (i) decreased amounts of a large number of polypeptides, (ii) increased accumulation of a comparatively few polypeptides and, (iii) appearance of ectomycorrhizins (mycorrhiza‐specific polypeptides). Approximately 50% of the fungal polypeptides and more than 80 % of the plant polypeptides resolved on gels disappeared during the development of ectomycorrhizas. Among 520 polypeptides, 10 polypeptides, called ectomycorrhizins, were ectomycorrhiza‐specific in that they were present in ectomycorrhizas, but not in free living mycelia nor in non‐infected roots. The results showed differential accumulation of ectomycorrhizins during mycorrhiza development. These findings demonstrate that protein synthesis is drastically altered in response to the morphological and physiological changes resulting from the establishment of ectomycorrhiza.
Root and mycorrhizal endophyte development in a chronosequence of restored tallgrass prairie
Authors: COOK B. D. , JASTROW J. D. , MILLER R. M. 
Published: April 2006

SUMMARYThe relationships between root and mycorrhizal development were investigated at the community level for a chronosequence consisting of restored tallgrass prairie (including plots in the second, fifth, eighth and eleventh growing season) and a virgin prairie remnant. Fibrous ( 1 mm diameter) root length increased across the chronosequence, with the greatest length occurring in the prairie remnant. After an initial increase between the second and fifth growing seasons, the percentage of fibrous roots colonized by vesicular‐arbuscular mycorrhizal fungi declined. However, this decline did not truly reflect the mycorrhizal association in this system because the length of fibrous roots colonized by mycorrhizal fungi did not decrease after the fifth growing season but instead remained essentially constant throughout the remainder of the chronosequence. Evaluation of the data by fibrous root size classes indicated that increases in root length and colonized root length occurred largely in the smaller size class (< 0.2mm diameter); in contrast, percentage colonization and the density of intraradical fungal structures was greater in the larger size class (0.2–1 mm diameter). The importance of thoroughly evaluating responses of mycorrhizal fungi relative to host responses was demonstrated in a field situation.
A comparative study of Geum rivale L. and G. urbanum L. to determine those factors controlling their altitudinal distribution
Authors: Graves J. D. , Taylor K. 
Published: April 2006

SUMMARYThe control of germination by temperature was compared in Geum urbanum L. and G. rivale L., two closely related species with contrasting altitudinal and latitudinal distributions. Under constant temperatures only slight differences were observed in the response of germination to temperature in the two species. A model was formulated to predict germination in field temperature conditions on the basis of rates of germination observed at constant temperatures. Comparison of observed and predicted germination under field temperature conditions revealed that the rate of germination was considerably higher than expected in G. urbanum at low temperatures. Calculations indicate that at altitudes above the altitudinal limit of G. urbanum this feature results in the germination of G. urbanum during the frost period of the year whilst seed of G. rivale remains dormant until the advent of milder climatic conditions.
Response of Armeria maritima (Mill.) Willd. and Plantago maritima L. from an Irish salt marsh to nitrogen and salinity
Authors: SHEEHY SKEFFINGTON M. J. , JEFFREY D. W. 
Published: April 2006

SUMMARYTwo experiments on the interaction between salinity and nitrogen supply were carried out on the halophytes Armeria maritima and Plantago maritima. Water potential values ranged from −0.16 MPa to – 5.0 MPa and nitrogen from 0.28 to 280 mg l−1 N. An increase in nitrogen above 2.8 mg l−1 N in the medium in all cases resulted in an increase in growth, though this was not so great at higher salinities. Armeria growth rate was optimal at a higher nitrogen concentration than Plantago and Armeria also accumulated nitrogen in shoots with increasing salinity. Plantago root nitrogen concentrations increased with increased nitrogen.Both species accumulated sodium in shoots, but in Armeria concentrations were lowest in the highest nitrogen treatments. Potassium was redistributed from shoots to roots with increasing salinity.Two populations of Plantago from the salt marsh were examined. Differences in growth response and flowering time were observed. A third, inland population of Plantago showed reduced vigour in water potentials lower than −2.5 MPa.
The Brière Marshlands: a palynological survey*
Authors: VISSET LIONEL 
Published: April 2006

SUMMARYThe work reported here allows the Holocene evolution of a large west French coastal marshland to be reconstructed and demonstrates the landscape changes associated both with the Flandrian transgression and the impact of human settlement from the Neolithic to the present. A sequence of markedly different stages is described, including estuary, schorre (salt marsh or zone of halophytic vegetation covered by the sea only at spring tides) and oak woodland, eventually yielding place to peat growth.
The palaeoecology of Alnus (alder) and the Postglacial history of floodplain vegetation. Pollen percentage and influx data from the West Midlands, United Kingdom
Authors: BROWN A. G. 
Published: April 2006

SUMMARYThe Postglacial history of Alnus is of particular relevance to the palaeoecology of wetlands and floodplains. The ecological histories of floodplain sites differ from those on dry‐land or from hydroseres. This paper uses pollen percentage and influx data to investigate floodplain succession and woodland development on floodplains in the West Midlands, the primary site being Wilden Marsh near Stourport, Worcestershire. The floodplain at Wilden probably underwent a three‐phase succession during the early Postglacial; Betula was replaced by Salix spp. which were out‐competed by Alnus. Alnus was present prior to its expansion, which is seen as the result of increasing soil stability, pedogenesis and decreased free drainage related to floodplain development and not necessarily to climatic change or anthropogenic disturbance. During the late Postglacial Alnus declines and Salix frequently increases again due to floodplain deforestation and utilisation, which was partly facilitated by altered soil conditions caused by hydrological change. The advantages of small floodplain sites for the differentiation of vegetation pattern is illustrated by the identification of a non‐floodplain pollen component dominated by Tilia.
Ascorbic acid‐induced progression of quiescent centre cells from G1 to S phase
Authors: LISO R. , INNOCENTI A. M. , BITONTI M. B. , ARRIGONI O. 
Published: April 2006

summaryQuiescent centre cells, which are known to have their cycle extended mostly in G, and to divide rarely, art‐stimulated to undergo DNA synthesis in root meristems of Allium cepa L. by treatment with ascorbic acid. The effect of ascorbic acid is dramatic: 21% of all the cells in the quiescent centre remain in the G, phase while 79% enter S phase. From a mean value of 2204 × 103μ3 in water‐grown roots, the volume of the quiescent centre drops to a mean value of 167 × 103μ3 following treatment with ascorbic acid. These results indicate that ascorbic‐acid stimulates not only the activity of the quiescent centre cells but also cell proliferation in the entire root meristem. The rate of cell progression through the cycle may be related to cellular ascorbic acid content.
Phenols and bud dormancy
Authors: CODIGNOLA ARNALDO , MAFFEI MASSIMO , FIESCHI MAURIZIO 
Published: April 2006

summaryQualitative analyses of the endogenous phenols of Fagus sylvatica L. were determined separately in leaf primordia and bud scales of dormant buds (apical, subapical and basal) of Fagus sylvatica L. until bud burst.Qualitative analyses in all leaf primordia showed the presence of phenols which are potential cofactors of IAA oxidase (vanillic acid, 2′4,4′‐trihydroxychalcone), uncoupling agents of oxidative phosphorylation (norwogonin, orobol 7‐O‐rhamnoglucoside, baicalin, 2′4,4′‐trihydroxychalcone and chlorogenic acid), a synergic stimulator of IAA (chlorogenic acid) and others. In all bud scales the qualitative phenol composition includes a mixture of potential IAA oxidase cofactors (vanillic acid and 2′,4,4′‐trihydroxychalcone), uncoupling agents (baicalin and 2′,4,4′‐trihydroxychalcone) and other compounds.In both leaf primordia and bud scales, the qualitative phenol composition does not change significantly during dormancy. These data do not indicate correlations between phenolic matabolism in bud scales and leaf primordia or between single phenolic compounds and the inception and maintenance of dormancy.
Phosphorus concentrations and chemical fractions in Eucalyptus seedlings grown for a prolonged period under nutrient‐deficient conditions
Authors: MULLIGAN D. R. 
Published: April 2006

summarySeedlings of Eucalyptus grandis Hill ex Maiden, two provenances of E. pilularis Smith (Coffs Harbour (CH) and Myall Lakes (ML)), and E. gummifera (Sol. ex Gaertner) Hochr. were grown for 60 weeks in sand culture under two nutrient‐limiting regimes. Under both levels of nutrient deficiency, E. pilularis (ML) and E. gummifera, the two species from phosphorus‐deficient sites, produced more dry matter than the other two species which originated in more fertile soils. Phosphorus partitioning among different organs, concentrations of phosphorus (and hence efficiencies of phosphorus use) and pool sizes of lipid‐P, Pi, ester‐P, nucleic acid‐P and residue‐P (bound P) were assessed in each organ at harvest. Concentrations were expressed on a per unit protein‐N basis (reflecting the amount of cytoplasm) as well as on a dry weight basis.At the more extreme conditions of nutrient deficiency (Treatment A), there was little difference between the leaves of the species in terms of efficiency of phosphorus use, but under the less severe conditions (Treatment B) efficiency was in the order E. gummifera > E. pilularis > E. grandis. Most of the foliar phosphorus (up to 70%) was present in a nucleic acid and ester form, although E. gummifera (and E. grandis for Treatment B) had a substantial phospholipid pool (approx. 25% of total leaf phosphorus). In the former case at least, this difference in phosphorus distribution among the chemical fractions may be of ecological significance. The stems and roots showed no species differences but noteworthy findings included the high residue‐P pool in the roots of Treatment A seedlings (up to 41% of root phosphorus) and the high concentrations of Pi in the stems of Treatment B plants (67–87 % of stem phosphorus).The ecologically distinct provenances of E. pilularis differed neither in phosphorus utilization efficiency nor in distribution among the molecular fractions examined. Their differing productivities were thus related to differences in phosphorus acquisition. The comparatively lower productivity of E. grandis was due to a combination of less efficient acquisition and less efficient internal utilization. The success of E. gummifera could be attributed to increased uptake and possibly increased utilization efficiency that in turn may have been related to its different phosphorus allocation pattern among the major chemical fractions.
Phosphate and nitrate movement in the clonal plants Lycopodium annotinum L. and Diphasiastrum complanatum (L.) Holub
Authors: HEADLEY A. D. , CALLAGHAN T. V. , LEE J. A. 
Published: April 2006

summaryThe uptake and movement of phosphate by Lycopodium annotinum L. in the field was studied using 32P‐labelled orthophosphate. Although over 90% of the phosphate taken up was retained in the incubated roots, the phosphate transported to the aboveground tissues showed extensive movements both distally and proximally along the horizontal branch system. Root systems up to 12 years old could transport phosphate as far as the stolon apex over one metre distally along the horizontal branch. The movement of phosphate is preferentially to the main sinks for phosphorus, the current year's horizontal and vertical branch segments.Nitrate uptake and movement was studied in Diphasiastrum complanatum (L.) Holub by measuring the induction of in vivo nitrate reductase activity in current year's growth in different parts of the clone. There was equal induction of in vivo nitrate reductase activity in 1–4 year old root systems incubated in nitrate, but absorption by 3 and 4 year old root systems induced the highest activities in the vertical branches. Nitrate movement to the stolon apex was only detectable from root systems up to 3 years old. There was considerable induction of nitrate reductase activity in vertical branch apices proximal to the 3 and 4 year old root systems supplied with nitrate. L. annotinum and D. complanatum show considerable inter‐module integration for nitrate and phosphate supply. This means that the plant can adopt an effective ‘foraging’ strategy for nutrients. The movement of resources from sites of absorption to their sites of utilisation means that there is extensive recycling of nutrients spatially, as well as temporally, within the habitats colonised by these plants.
Water uptake and movement in the clonal plants, Lycopodium annotinum L. and Diphasiastrum complanatum (L.) Holub
Authors: HEADLEY A. D. , CALLAGHAN T. V. , LEE J. A. 
Published: April 2006

summary Lycopodium L, sensu stricto and Diphasiastrum complanatum (L.) Holub demonstrate a ‘guerilla’ growth strategy whereby the growth of the stolon apex is subsidized by resources from root systems several years old. In the dry sub‐arctic/sub‐alpine birch forests of Swedish Lapland where the soil cover is very heterogeneous and the annual precipitation is low, the subsidized water balance of the stolon apex is critical to the survival of the plant. Some aspects of water relations of L. annotinum L. and D. complanatum (L.) Holub were studied in the field.Water potentials were more negative towards the stolon apex, and water movement, traced using acid fuchsin dye, showed that the dye moved 14 times further from an isolated root system in a distal direction towards the stolon apex than in the proximal direction. A single root system initiated 8 years previously, and 65 cm from the stolon apex, was shown to be capable of supporting the growth of this apex. The excision of 3 and 4 year old root systems resulted in the greatest effect on depression of the water potential of the stolon apex, suggesting that these provided most of the water used by the stolon apex.The preferential allocation of water to the stolon apex was very effective, and the functional morphology of the plants seems to be related to harsh, patchy environments. However, when crossing large patches of inhospitable terrain, or under periods of drought, those stolon apices dependent on old, distant root systems for their water supply can experience lethal water stress. As the health of the stolon apex effects its degree of correlative inhibition of sub‐dominant stolons, the architecture and foraging ability of the clone is affected.
Non‐uniform stomatal closure induced by water stress causes putative non‐stomatal inhibition of photosynthesis
Authors: DOWNTON W. J. S. , LOVEYS B. R. , GRANT W. J. R. 
Published: April 2006

summaryThe partial pressure of intercellular CO2 derived from gas exchange data for water‐stressed grapevine (Vitis vinijera L.), oleander (Nerium oleander L.) and red‐flowering gum (Eucalyptus ficifolia F. Muell.) does not indicate the actual average intercellular CO2 of the leaf. This can be determined from chlorophyll fluorescence signals and modelled from conventional gas exchange information. Water stress increases endogenous levels of abscisic acid and the leaves respond in a similar manner to that observed when exogenous abscisic acid is applied. Autoradiograms show that water stress results in non‐uniform gas exchange over small areas of the leaf. Non‐uniform stomatal closure can account for the apparent non‐stomatal inhibition of photosynthesis in plants experiencing water stress.
Kinetics of inhibition of foliar gas exchange by exogenous ethylene: an ultrasensitive response*
Authors: GUNDERSON CARLA A. , TAYLOR GEORGE E. 
Published: April 2006

summaryThe objective of this study was to examine the inhibition of foliar gas exchange as a function of ethylene (C2H4) concentration in order to evaluate the potential role of stress C2H, in mediating changes in gas exchange in response to environmental stress. Net photosynthesis (PN) and stomatal conductance to H2O vapour (gs H2o) were measured in soybean (Glycine max (L.) Merr cv. Davis) seedings after a 4 h exposure to one of a range of exogenous C2H4 concentration (0–20μII−1)in a controlled environment system. Declines in both Ps and gs H2O shifted from first‐order (liner decline) to zero‐order (saturation response) with increasing C2H4 concentration. The response of gs H2O to C2H4, was more pronounced than the response of Ps, with maximal declines for gs H2O of 32–48%, and half‐maximal response at 0.15μII−1. Corresponding parameters for PN were 18–29%, inhibition and half‐maximal response at 0–35μII−1. Both response curves were similar to those documented for C2H4, binding and for hormonally mediated C2H4 actions. Kinetic analysis of the saturation patterns by the Hill equation showed both responses to be ultrasensitive, i.e. they provide a relatively large change in gas exchange for a small change in C2H4 concentration. Based on this ultrasensitivity, we propose that endogenous stress C2H4 mediates some of the responsiveness of gas exchange to environmental stresses of natural and anthropogenic origin.
Prediction of the probability of forest decline damage to Norway spruce using three simple site‐independent diagnostic parameters
Authors: MEHLHORN H. , FRANCIS B. J. , WELLBURN A. R. 
Published: April 2006

summarySurvey data for Norway spruce (Picea abies I.) trees at 12 different forest sites across Europe have been analysed. Three variables (dry weight/fresh weight ratio differences between current and two‐year‐old needles, ethylene emissions and violaxanthin/antheraxanthin ratios) were found which together show a significant relationship to tree damage in areas affected by forest decline and which are independent of site effects (P < 0.001). Results are also presented that support the contention that atmospheric pollution, especially tropospheric ozone, is the major cause of this problem. After a four‐year fumigation experiment, 12‐year‐old Norway spruce trees showed similar cellular changes as those found in the 30‐to 40‐year‐old trees of the survey affected by forest decline. In the fumigation experiment, these changes were most pronounced in those plants exposed to a combination of treatments including ozone, sulphur dioxide and acid rain. The pollutant concentrations used in the four‐year study were representative of those experienced by trees growing in affected areas.