bluuebunny/crossref_metadata_2025_split huggingface dataset:
Purification and characterization of invertases from leaves of Lolium temulentum
Authors: WALKER R. P. , WINTERS A. L. , POLLOCK C. J. 
Published: March 2003

SUMMARYLeaves of Lolium temulentum L. contain both low and high pI acid invertases. Immunoblot analysis of a highly purified preparation of these forms suggested that they both possess a subunit molecular weight of 68 kDa. Protoplasts and their derived vacuoles were isolated from leaf blades and contained sufficient acid invertase activity to account for all the activity found in the soluble fraction of crude homogenates of leaf blades. Alkaline invertase was present in the basal region of leaves and, unlike acid invertase, did not bind to Con A‐Sepharose, suggesting that the acid invertase was a glycoprotein and that the alkaline invertase was not. Fructose inhibited both acid and alkaline invertases. The hypothesis is discussed that activity in vivo could be modulated by the concentration of free fructose.
Seasonal variation of fructan‐β‐fructosidase (FEH) activity and characterization of a β‐(2‐1)‐linkage specific FEH from tubers of Jerusalem artichoke (Helianthus tuberosus)
Authors: MARX STEFAN P. , NÖSBERGER JOSEF , FREHNER MARCO 
Published: March 2003

SUMMARYThe fructan‐β‐fructosidase activity (1‐FEH; EC 3.2.1.80) that degrades inulin in tubers of Helianthus tuberosus L. appears to be developmentally regulated; it was low in growing tubers but increased during dormancy and sprouting. In spite of relatively high 1‐FEH activity in vitro, fructose concentration was very low in developing and dormant tubers and increased markedly only during sprouting. A fructan‐β‐fructosidase from such sprouting tubers was purified 41‐fold to a single protein band on one‐dimensional sodium dodecylsulphate‐polyacrylamide gels. The purification procedure included ammonium sulphate precipitation, lectin‐affinity chromatography on concanavalin A, anion‐exchange and cation‐exchange chromatography. The enzyme had an apparent molecular mass of 75000 measured by size‐exclusion chromatography, and 79000 measured by one‐dimensional sodium dodecylsulphate‐polyacrylamide gel electrophoresis. It exhibited a high substrate specificity, hydrolysing terminal β‐(2‐1)‐fructosyl‐fructose‐linkages in linear and branched fructan oligomers; β‐(2‐6)‐linkages were hardly hydrolysed. Hydrolysis of inulin oligomers followed normal saturation kinetics: Km values for 1,1‐kestotetraose and 1,1,1‐kestopentaose were 8‐3 mM and 12 mM, respectively. Fructosyl residues were hydrolysed from inulin oligomers by a multi‐chain mechanism. The fructan‐β‐fructosidase showed optimal enzyme activity at pH 5–2, and it retained its full activity after pre‐incubation for 1 h at up to 40°C. The release of fructose from 5 mm 1,1‐kestotetraose was reduced by 25 % when 1‐FEH was assayed in the presence of 10 mM sucrose. It is proposed that the inhibition of 1‐FEH activity by sucrose is a mechanism for controlling fructan degradation in planta.
Copper and nickel uptake, accumulation and tolerance in Typha latifolia with and without iron plaque on the root surface
Authors: YE Z. H. , BAKER A. J. M. , WONG M. H. , WILLIS A. J. 
Published: March 2003

summaryThe effects of iron plaque on the growth of Typha latifolia L. and accumulation of copper and nickel in T. latifolia were investigated under laboratory conditions in nutrient solution cultures. Seedlings with and without iron plaque on their roots were exposed to 0.05 μg ml−1 Cu and 0.10 μg ml−1 Ni solutions for 72 d. The results showed no differences in root and shoot d. wt and leaf elongation when Cu or Ni were added to the solution and in the presence or absence of plaque. However, root length was reduced by Cu and Ni, and the reduction in root length was greater in the presence of plaque. Some Cu and Ni was adsorbed on root surfaces; roots with plaque took up more Cu, but less Ni than those without. The presence of plaque did not alter Cu uptake and translocation but increased Ni uptake and translocation. Most of the Cu and Ni taken up was retained in the roots, suggesting that the root tissue rather than the root surface or plaque is the main barrier for Cu and Ni transport. The results differ from those reported for other species.
Effects of the spatial arrangement of aerial stems and current‐year shoots on the demography and growth ofHydrangea hirtain a light‐limited environment
Authors: ISHII HIROAKI , TAKEDA HIROSHI 
Published: March 2003

summaryThis study investigates the effects of the spatial arrangement of aerial stems and current‐year shoots on patterns of herbivory, competition and on the requirements for mechanical support inHydrangea hirtaSieb. et Zucc. growing in a light‐limited environment. Stem demography was followed for three consecutive growing seasons. Stem mortality rates decreased with increasing stem age. Age‐specific mortality rate was highest for new stems owing to the high incidence of herbivory. Mortality due to herbivory was low in older stems and was attributed to the dispersion of the risk of herbivore attack as a result of the increase in number of current‐year shoots per stem. Clumping of stems led to intense intra‐clonal competition as inferred from size‐dependent mortality and density‐dependent turnover of stems, and higher maximum stem length in clumps with higher stem density. Analysis of the spatial distribution of current‐year shoots within the stem crown revealed a uniform, mono‐layered crown architecture. The horizontal distribution of buds within the mono‐layer was aggregated as a result of their opposite position, but as current‐year shoots grew, their apices became uniformly distributed, resulting in efficient leaf display for light capture and shading out competing stems. However, limits on stem growth were observed in crown expansion, shoot production rate and current‐year shoot size. Crown width increased with increasing basal diameter to reach a maximum. Both shoot production rate and current‐year shoot size decreased with stem growth and a minimum current‐year shoot size was defined. These limits on stem growth were attributed to suppression from intra‐clonal competition and to the requirements for mechanical support of the mono‐layered crown.
Relationships between ozone resistance and climate in European populations of Plantago major
Authors: LYONS TOM M. , BARNES JEREMY D. , DAVISON ALAN W. 
Published: March 2003

summaryThe relative ozone resistance of 20 European and two American populations of Plant ago major was examined, and relationships with climatic factors at the source of the plant material were explored using data provided by participants in the ICP‐Crops initiative (International Co‐operative Programme to Investigate the Effects of Air Pollutants and Other Stresses on Agricultural and Semi‐Natural Vegetation). Plants grown from seed were exposed to either charcoal/Purafil® filtered air (CF < 5 nmol mol−1 O3) or CF + ozone (70 nmol mol−1 O3 7 h d−1) over a 2‐wk period in controlled environment chambers, and effects on mean plant relative growth rate (R) and allometric root/shoot growth (K) determined. Ozone resistance (R%) was calculated from (R03/RCF) × 100.Populations exhibited contrasting sensitivities to ozone, without the development of typical visible symptoms of injury. A positive relationship was found between relative ozone resistance and descriptors of the ozone‐climate at the site of seed collection for the year of, and the 2 yr before, seed collection. The best predictors of inherent ozone resistance were shown to be cumulative ozone exposure indices calculated according to current United Nations Economic Commission for Europe (UN‐ECE) critical level guidelines for the pollutant (i.e. the accumulated hourly average ozone exposure over a threshold level of 40 nmol mol−1 (AOT40) or 30 nmol mol−1 (AOT30) calculated during daylight hours for the consecutive 3‐month period of the year experiencing the highest ozone concentrations). No relationships were found between ozone resistance and climatic factors (temperature, precipitation, sunshine hours, humidity) or the concentrations of other air pollutants (SO2, NO2, NO).These findings support the view that current ambient levels of ozone in many regions of Europe are high enough to promote evolution of resistance to the pollutant in native plant populations. The significance of these findings to the debate over the establishment of separate critical levels for the protection of natural and semi‐natural vegetation is discussed.
Water uptake by safflower and wheat roots infected with arbuscular mycorrhizal fungi
Authors: BRYLA D. R. , DUNIWAY J. M. 
Published: March 2003

SUMMARYThe objective of this study was to determine if infection by arbuscular mycorrhizal fungi alters water uptake by roots under well watered to severely droughted conditions. Safflower and wheat plants were grown with and without the mycorrhizal fungi, Glomus etunicatum or G. intraradices in nutrient‐amended soil under environmentally controlled conditions to yield mycorrhizal and non‐mycorrhizal plants with similar leaf areas, root length densities, d. wt, and adequate tissue phosphorus and nitrogen. Specific water uptake rates (cm3 of water cm−1 root length d−1) were estimated non‐destructively at various depths in the soil from changes in the soil water content measured using a gamma attenuation method. When soil water was severely depleted, changes in soil water potentials were also measured with soil psychrometers. Roots from both plant species extracted water at the fastest rate from the upper soil layers when the soil water content was high, and later, extracted water primarily from deeper depths as water in the upper soil layers was depleted. Mycorrhizal infection did not affect the rates at which roots extracted water from soil whether soil moisture conditions were at their wettest condition, at container capacity, or at the driest extreme when soil water potentials ranged from −1.5 to −2.0 MPa and the plants were completely wilted. Plant water relations were also largely unaffected by infection. Mycorrhizal infection did not alter the ability of plants to extract water from soil even during extreme drought.
A cytogenetic approach to the improvement of aluminium tolerance in wheat
Authors: MILLER T. E. , IQBAL N. , READER S. M. , MAHMOOD A. , CANT K. A. , KING I. P. 
Published: March 2003

summaryHigh levels of soil aluminium place serious constraints on wheat production on acidic soils, especially in the tropical areas of Africa and South America. Conventional plant breeding has improved the tolerance of the wheat crop, but available genetic variation is limited. The wild relatives of wheat provide a valuable gene pool for the introduction of further genetic variation. One wild species, Aegilops uniaristata Vis. (2n = 2x = 14,NN), is being utilized as a new source of tolerance. Of the addition lines of individual N genome chromosomes of A. uniaristata to wheat (Triticum aestivum L.) which have been established and characterized, chromosome 3N has been shown to confer tolerance to wheat. The three substitution lines in which 3N replaces the homoeologous wheat chromosomes, 3A, 3B or 3D, have also been produced. Growing plants to maturity in a low pH/high Al hydroponics system confirmed that chromosome 3N conferred tolerance to the substitution lines as well as to the addition line. By manipulating the genetic control of homoeologous chromosome pairing, chromosome 3N is being recombined with its wheat homoeologues in order to introduce a smaller alien segment which carries the gene(s) for tolerance but not the agronomically unacceptable brittle rachis gene also carried on chromosome 3N.
Markers and mapping: we are all geneticists now
Authors: JONES NEIL , OUGHAM HELEN , THOMAS HOWARD 
Published: March 2003

summaryThis is a review of genetic mapping with molecular markers aimed at the non‐specialist who wishes to use, or at least grasp the concepts behind, this powerful analytical tool. Restriction fragment length polymorphisms (RFLPs) are defined and used to illustrate the different aspects of mapping. The principles of segregation, recombination and linkage are considered and related to the idea of a molecular marker map. A description of a typical mapping population and how it is analysed follows. Traits to be mapped are divided into those controlled by ‘major’ genes and those governed by quantitative trait loci (QTLs). Exploitation of the map for marker‐assisted selection, gene cloning and synteny comparisons is discussed, as are some of the limitations to the usefulness of molecular marker maps. Finally other marker systems are introduced, namely minisatellites or variable number tandem repeats (VNTRs); randomly amplified polymorphic DNA (RAPDs); microsatellites or simple sequence repeats (SSRs); and amplified fragment length polymorphisms (AFLPs).
The plant cell wall is altered by inhibition of polyamine biosynthesis
Authors: BERTA G. , ALTAMURA M. M. , FUSCONI A. , CERRUTI F. , CAPITANI F. , BAGNI N. 
Published: March 2003

summaryPolyamines (PAs) and the cell wall have important roles in plant morphogenesis. An interaction between cell wall components (pectic substances) and polyamines is known and inhibition of polyamine biosynthesis induces inhibition of some morphogenic processes. This is the case of rhizogenesis in tobacco (Nicotiana tabacum L.) thin layers. This paper investigates whether inhibition of polyamine biosynthesis induces modifications in the structure, shape and size of the primary cell walls in tobacco thin layers cultured on a rhizogenic medium, and whether polyamines (putrescine and spermidine) administered in combination with their corresponding inhibitors dl‐α‐difluoromethylomithine +dl‐α‐difluoromethylarginine (DFMO + DFMA), cyclohexylamine (CHA), methylglyoxal‐bis(guanylhydrazone) (MGBG) restore cell wall characteristics. In treatments with polyamine inhibitors, cell hypertrophy occurred in the lowermost layer of the explant in contact with the medium. Many unusual features were observed in the walls of the hypertrophic cells: an amorphous structure, loosening of the fibrillar component; detachment between contiguous cells, lysis of wall components and an uneven thickness often giving a wavy appearance (in transverse walls). The inhibitors reduced cell wall thickness, and caused a weak positive PATAg reaction for polysaccharides. Polyamines restored cell wall thickness and, in general, the other wall features. Our results show that polyamines are necessary for maintaining cell wall characteristics by strengthening the links between cell‐wall components.
Growth and survival of Azolla filiculoides in Britain I. Vegetative production
Authors: JANES RACHEL 
Published: March 2003

Azolla filiculoides Lam. causes serious weed problems in Britain, but its long‐term survival might be limited by winter death. The aim of this study was to establish the low temperature responses and limitations of A. filiculoides sporophytes.In the laboratory, normal vegetative growth was shown to continue at 5°C. Reddening of plants was a response to low temperature and high light conditions which could be prevented by shading. Adult plants died after short (18 h) exposure to −4°C but survived sub‐zero temperatures >−4°C. Evidence was found of seasonal changes in chill tolerance, but not in freeze tolerance.In outdoor culture, plants survived encasement in ice and air temperatures to −5°C. Additional evidence suggested that natural populations can readily survive air temperatures much lower than this. Microclimatic effects are likely to be responsible for this discrepancy between laboratory and outdoor culture results.Three phenotyes were identified; survival, colonizing and mat forms.
Sensitivity to and requirement for iron in Plantago species
Authors: SCHMIDT W. , FÜHNER C. 
Published: March 2003

The relative importance of some aspects of iron nutrition for the distribution of six Plantago species (P. maritima L., P. coronopus L., P. major ssp. major L., P. serpentina All., P. media L. and P. lanceolata L.) with different habitat requirements for soil pH and moisture was evaluated. Iron efficiency and Fe tolerance of hydroponically‐grown plants were assessed by determining the decrease in relative growth rates caused by suboptimal and supra‐optimal external Fe concentrations. Marked interspecific differences were observed in visual symptoms of Fe deficiency and Fe toxicity and in the external Fe concentrations leading to 50% inhibition of maximal relative growth rates (rgr50%). Whereas P. serpentina displayed a clear preference for low external Fe concentrations, growth rates of P. maritima and P. media were found to be increased at higher concentrations. Severe growth restriction at both low and high Fe concentrations was evident in P. lanceolata and P. major. A broad optimum was observed in P. coronopus exhibiting a low external Fe requirement and a high tolerance to supra‐optimal Fe concentrations. Iron efficiency and Fe tolerance differed in a way which was only partly correlated with the expected Fe availability at the natural habitat of the species, suggesting that Fe concentrations are of minor importance for their distribution, or that some of the mechanisms that render Fe oxides available for uptake in situ are masked in solution experiments.To gain insight into the impact of the physiological and morphological characteristics of the species on Fe efficiency, the effect of Fe status on shoot∶root ratio, relative root surface area, root Fe(III) reductase and proton extrusion capacity were investigated. Roots of all species showed increased Fe chelate reduction activity upon growth at suboptimal Fe concentrations; marked differences were observed with respect to the kinetic parameters of the reductase. Maximal velocity of the reduction was positively correlated with relative growth rate and was not related to the Fe efficiency of the species. By contrast, Km corresponded to Fe efficiency ranking and can therefore be regarded as an important parameter for the uptake of Fe at low availability. Enhanced ability to acidify the rhizosphere was only observed in P. major. From the morphological characteristics investigated, root surface area appears to be the most important parameter in the uptake of Fe at suboptimal external concentrations.
Nuclear ribosomal sequence analysis ofOidiodendron: towards a redefinition of ecologically relevant species
Authors: Lacourt Isabelle , Girlanda Mariangela , Perotto Silvia , Del Pero Massimiliano , Zuccon Dario , Luppi Anna Maria 
Published: March 2003

Summary• Nuclear ribosomal sequence analysis was performed to investigate delimitation of commonOidiodendronspecies comprising endomycorrhizal symbionts and close associates of ectomycorrhizal plants.• Neighbour‐joining, maximum likelihood and parsimony analyses were used to compare 35 ribosomal DNA (internal transcribed spacer (ITS) and 5.8S) sequences (including sequences available in databases) from 15 putative species.• Oidiodendron citrinumformed a monophyletic group nested withinO. maius, whereasO. tenuissimumandO. griseumdid not appear either as distinct groups or as a single complex. Pairwise nucleotide divergence values betweenO. citrinumandO. maiuswere very low and comparable to intraspecific values obtained for both species; values forO. griseumandO. tenuissimum, although higher, overlapped those observed at the intraspecific level for the two species.• Molecular data indicate thatO. maiusandO. citrinum, which were described as distinct, though related species, could be moved to a subspecific level; however, the delimitation ofO. griseumandO. tenuissimumis still open to question. Taxonomic rank assignment to groups determined from sequence data analysis is discussed.
Productivity of Trifolium subterraneum and Phalaris aquatica under warmer, high CO2 conditions
Authors: Lilley J. M. , Bolger T. P. , Gifford R. M. 
Published: March 2003

Summary

Despite the importance of grass‐legume pastoral ecosystems worldwide, there is little known about the impacts of concurrent increase in temperature and atmospheric CO2 concentration on their productivity.
Pure and mixed swards of subterranean clover (Trifolium subterraneum) and phalaris (Phalaris aquatica) were established under ambient and warmed (+3.4°C) air temperatures, at ambient and 690 µmol mol−1 CO2 concentrations in field tunnels in temperate south‐eastern Australia.
Over one year, elevated CO2 increased clover foliage growth in the monoculture by 19%, and by 31% in the mixture. Warming reduced clover monoculture herbage production at ambient CO2 by 28% and reduced the growth enhancement by elevated CO2 to +8%. Forage growth of phalaris monoculture was not affected significantly by either factor. Forage growth of the mixture was increased by 34% in response to higher CO2, but unaffected by warming. Elevated CO2 combined with warming increased forage growth of the mixed sward by 23%.
Concurrent rise in atmospheric CO2 concentration and temperature increased productivity of subterranean clover‐phalaris swards. However, longer term effects on species competition and persistence may modify this conclusion.
Differential expression of the hexose‐regulated fungal genes AmPAL and AmMst1 within Amanita/Populus ectomycorrhizas
Authors: Nehls Uwe , Bock Andrea , Ecke Margret , Hampp Rüdiger 
Published: March 2003

Summary

At least three fungal ‘networks’ are formed in ectomycorrhizal symbiosis: the Hartig net, the sheath and extramatrical hyphae. Since these structures have different functions regarding uptake, storage and partitioning of carbohydrates and nutrients, regulation and coordination of metabolic fluxes are of special interest for ectomycorrhizal functioning.
To get some insight into structure‐specific functions, the Amanita fungal sheath was separated by microdissection from the remaining Populus roots that still contained the Hartig net. Expression of the genes coding for phenylalanine ammonium lyase (AmPAL) and hexose transporter (AmMst1) was investigated separately for both structures by RT‐PCR.
When constitutively expressed fungal genes were used as a control, the expression of AmMst1 was enhanced about six‐fold in hyphae of the Hartig net compared with those of the fungal sheath. By contrast, AmPAL was only barely detectable in the Hartig net, but highly expressed in the fungal sheath.
Since in pure fungal culture both genes are regulated by monosaccharides, it is supposed that an apoplastic hexose gradient, between hyphae of the Hartig net and those of the fungal sheath, might regulate fungal gene expression and thus hyphal physiology within ectomycorrhizas.
Isolation and phylogenetic identification of a dark‐septate fungus associated with the alpine plantRanunculus adoneus
Authors: Schadt Christopher W. , Mullen Renée B. , Schmidt Steven K. 
Published: March 2003

Summary Dark‐septate endophytic (DSE) fungi are ubiquitous in the roots of Arctic and alpine plants, yet very little is known about their phylogenetic identities or effects on their host plants. Several such fungi were isolated from the alpine snowbed plantRanunculus adoneusin the Front Range of Colorado, USA; one isolate was chosen for detailed study. The ability of this isolate to re‐colonize plant roots in pot cultures was assessed, and phylogenetic analyses were performed using small‐subunit (SSU), 5.8S and internal transcribed spacer (ITS) 2 ribosomal DNA sequences. This isolate had the ability to produce root endophytic structures in pot cultures similar to those reported from other sources and observed inR. adoneusroots. SSU phylogenetic analyses showed this isolate to be related to a clade within the Euascomycetes containing the Leotiales and Erysiphales. In addition, SSU and 5.8S–ITS2 sequences showed high phylogenetic similarity to a variety of isolates reported from other plants of diverse geographical origins. Although most of these isolates remain unidentified, one closely related isolate was the anamorphic taxonPhialophora gregata. The results suggest that this DSE isolate might belong to the fairly closely related group of plant endophytes that have varied effects on the plants that they inhabit.