bluuebunny/crossref_metadata_2025_split huggingface dataset:
Localization of β (1–3) glucan in walls of the endomycorrhizal fungi Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe and Acaulospora laevis Gerd. & Trappe during colonization of host roots
Authors: LEMOINE M. C. , GOLLOTTE A. , GIANINAZZI‐PEARSON V. 
Published: April 2006

summaryPrevious studies showed that cell walls of endomycorrhizal fungi belonging to the Acaulosporaceae and Glomaceae contain β (1–3) glucan polymers as well as chitin. Indirect immunolabelling with monoclonal and polyclonal antibodies has been used to investigate the distribution of these structural polysaccharides in cell walls of Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe and Acaulospora laevis Gerd. & Trappe as they interact with pea and tobacco roots, respectively. The (l‐3) glucans were detected in the walls of external hyphae, and of hyphal coils and intercellular hyphae developing in outer root tissues. The glucan component was alkali‐insoluble but treatment with chitinase resulted in solubilization of most of the β(1–3) glucans from the fungal wall. A decrease in immunolabelling was associated with thinning out of the hyphal wall as the fungi colonized deeper in the host root, and β(1–3) glucans could not be detected in walls of intercellular hyphae or arbuscules in the parenchyma cortical tissue. The molecular configuration of cell walls of G. mosseae and A. laevis is discussed in relation to fungal morphogenesis and the symbiotic state in endomycorrhiza.
Soil phosphate status modifies response of mycorrhizal and non‐mycorrhizal Senecio vulgaris L. to infection by the rust, Puccinia lagenophorae Cooke
Authors: WEST H. M. 
Published: April 2006

summaryThe impact of rust infection (Puccinia lagenophorae Cooke) on growth of mycorrhizal and non‐mycorrhizal Senecio vulgaris L. was examined under three levels of phosphorus fertilization. Seeds were then collected from infected and control plants and germination, seed chemistry and offspring vigour were examined. Rust infection did not become established on plants which were phosphorus limited, but on hosts fed with medium or high levels of P, the proportion of total leaf number exhibiting infection was a function of leaf production. Capitula production was decreased by rust infection and increased by mycorrhizal colonization in plants fed with a medium concentration of P. In plants fed with a high P concentration, leaf number was reduced by rust infection of mycorrhizal plants, whilst rust was deleterious to both mycorrhizal and non‐mycorrhizal plants grown with a medium P supply. However, the effects of the rust were less marked in the mycorrhizal plants. Seed production and weight were unaffected by fungal treatments, although percentage germination of the resultant seeds was reduced by maternal mycorrhizal colonization and enhanced in seed from rusted, mycorrhizal plants grown at high soil P. The amount of total C, N and P was also reduced by maternal mycorrhizal infection at high soil P and increased in seeds from rusted, mycorrhizal mothers. Vigour of offspring produced from treated mother plants was influenced by mycorrhizal × phosphorus and rust × phosphorus interactions with respect to bud and leaf numbers. Mycorrhizal infection of mother plants grown with a medium P supply benefited the offspring as increased leaf and bud production was observed, but rusted mothers at the same P level produced offspring with reduced leaf number and potential fecundity.
Comparison of hydraulic architecture of woody plants of differing phylogeny and growth form with special reference to freestanding and hemi‐epiphytic Ficus species from Panama
Authors: PATIÑO SANDRA , TYREE MELVIN T. , HERRE E. ALLEN 
Published: April 2006

summaryHydraulic parameters were measured in seven species of Fiats (three free‐standing and four hemi‐epiphytic) on stem segments of 3–35 mm in wood diameter. Parameters measured included Kh (water flux per unit pressure gradient), Kh (leaf specific conductivity =Kh per unit leaf area), Ks (specific conductivity =Hh per unit wood cross section), and Hv (Huber value = wood cross section per unit leaf area).The hemi‐epiphytes tended to have less conductive stems per unit leaf area (lower Ki and invested less wood cross section per unit leaf area (lower Hv) than free‐standing species. Hydraulic parameters of Ficus are compared to 21 other temperate and tropical species to see if there is any discernible pattern in hydraulic architecture that correlates with phylogeny, growth form or habitat occupied by diverse species. Figs, as a group, had relatively high hV. and relatively low hv compared to other tropical trees.A possible correlation between KL and transpiration and growth form is discussed.
Growth and dry matter partitioning in loblolly and ponderosa pine seedlings in response to carbon and nitrogen availability
Authors: GRIFFIN KEVIN L. , WINNER WILLIAM E. , STRAIN BOYD R. 
Published: April 2006

summaryWe grew loblolly pine (Pinus taeda L.) and ponderosa pine (Pinus ponderosa Dougl. ex Laws.) seedlings in a factorial experiment with two CO2 partial pressures (35 and 70 Pa) and two nitrogen treatments (1‐0 and 3–5 mM NH4+) for one growing season in a ‘common garden’ experiment designed to examine the extent that dry matter and nitrogen accumulation and partitioning are environmentally controlled. Ponderosa pine seedlings grown in 35 Pa CO2 and 3.5 mM NH4+ showed symptoms of nitrogen toxicity, characterized by greatly reduced growth, and moderately reduced total plant N. With the exception of this treatment combination, there were no significant differences between species in total plant dry matter or total plant nitrogen, suggesting that responses of growth to environmental conditions were stronger than heritable responses. There were however large differences in dry matter and N partitioning between the two species. Increases in leaf mass were largest in loblolly pine, whilst ponderosa pine tended to have higher root: shoot (R:S) ratios. R:S ratio of loblolly increased in response to C availability and decreased in response to N availability, whilst R: S ratio of ponderosa pine was much less responsive to resource availability. Total plant N varied with N supply, and N partitioning was related to plant growth and carbon partitioning. Carbon and N were interactive, such that an increase in the accumulation of either resource was always accompanied by an increase in the other. Over several seasons the different patterns of resource acquisition and biomass allocation that we observed in a uniform environment could potentially result in different growth rates at most resource levels. In the first season, contrary to our expectations, heritable differences in growth rate did not appear.
The combined effect of arbuscular mycorrhizas and short‐term cold exposure on wheat
Authors: PARADIS R. , DALPÉ Y. , CHAREST C. 
Published: April 2006

summaryIn order to investigate the effect of arbuscular mycorrhizal colonization and short‐term cold exposure on Triticum aestivum L., 7‐wk‐old seedlings of spring and winter cultivars (Glenlea and AC Ron) were submitted to a 1‐wk cold treatment when inoculated with Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe. The combined effect of arbuscular mycorrhizas and low temperature on the two cultivars was determined for several physiological parameters including biomass and chlorophyll, protein, and sugar contents. The dry biomass was higher in Glenlea than AC Ron at week five and did not significantly change at week eight in both cultivars with either the mycorrhizal or the cold treatment. The chlorophyll content was higher in mycorrhizal (M +) than non‐mycorrhizal (M‐) Glenlea at 5 °C but was unaltered in AC Ron or in either cultivar at 25 °C. The reducing and total sugar contents were higher in AC Ron than Glenlea. The non‐reducing sugar level at 5 °C was higher in M + AC Ron than M+ Glenlea and higher in M‐ than M+ Glenlea. The protein content was higher in Glenlea than AC Ron at 25 °C but remained constant regardless of the mycorrhizal or cold treatment. This study shows that the spring wheat seems to benefit more than the winter wheat from AM association after a short‐term exposure to low temperature.
Arbuscular mycorrhizas and water relations in maize under drought stress at tasselling
Authors: SUBRAMANIAN K. S. , CHAREST C. , DWYER L. M. , HAMILTON R. I. 
Published: April 2006

summaryA greenhouse experiment was conducted to investigate the influence of an arbuscular mycorrhizal (AM) fungus (Glomus intraradices Schenck & Smith) on drought tolerance in tropical maize. Freshly regenerated seeds of selection cycles 0 (cv. C0, drought‐sensitive) and 8 (cv. C8, drought‐resistant) of the lowland tropical population ‘Tuxpeño sequia’ were used for this study. Maize plants were subjected to drought stress for three weeks following tasselling (75–95 days after sowing). During the drought stress period, midday leaf water potential (LWP), stomatal resistance (SR) and transpiration rate (TR) were monitored daily, and green leaf area (GLA) determined at alternate days to assess the effects of mycorrhizal inoculation. Mycorrhizal plants of the cultivars CO and C8 had higher (less negative) LWP and TR, and lower SR throughout the experiment. The GLA was 27.5 % higher in mycorrhizal than non‐mycorrhizal CO plants under drought conditions. Results indicate that mycorrhizal significantly improve tolerance to moderate drought stress imposed at tasselling, especially for the sensitive CO maize cultivar.
The role of plant‐parasitic nematodes and soil‐borne fungi in the decline of Ammophila arenaria (L.) Link
Authors: DE ROOIJ‐VAN DER GOES P. C. E. M. 
Published: April 2006

summaryIn coastal foredunes, Ammophila arenaria (L.) Link grows vigorously when it is buried regularly by windblown sand and degenerates at stabilized sites. Nematodes and soil‐borne fungi were found to be involved in its decline. In order to establish their role in the disease complex, seedlings of A. arenaria were inoculated with several groups of potentially harmful soil organisms that were isolated from its root zone. Inoculation of single species of fungi did not reduce the growth of the seedlings, but combining all fungi that were commonly found in the Dutch coastal foredunes significantly reduced growth to about 80% of that in sterilized soil. This indicates synergistic effects between commonly found plant pathogenic fungi. The addition of large numbers of the nematode Telotylenchus ventralis, the only species that could be successfully grown on A. arenaria in the laboratory, reduced plant growth to the same level as in non‐sterile soil, but numbers were 80 times greater than in the latter soil. Inoculation with relatively large numbers of T. ventralis in combination with the commonly occurring fungi reduced plant growth in sterilized soil to a level similar to that in non‐sterile soil. The involvement of other species of nematodes, such as Heterodera spp. or Meloidogyne maritima, in the decline of A. arenaria in non‐sterile soil could not be proven in inoculation experiments with sterile soil, but it is likely that these species may also be involved. It is concluded, therefore, that several different combinations of soil organisms can be harmful to A. arenaria, so that natural decline is not caused by one simple well defined pathosystem.
Stimulation and inhibition of pine root growth by osmotic stress
Authors: TRIBOULOT MARIE‐BÉATRICE , PRITCHARD JEREMY , TOMOS DERI 
Published: April 2006

summaryThe effect of osmotic stress on the regulation of extension of roots of pine seedlings (Pinus pinaster Ait.) was studied. Extension rate (r) was measured as increase in root length, and as local growth rate (LGR) along the growing region. Turgor pressure (P) was measured over the same profile using the cell pressure probe. Correlation of LGR and P allowed changes in cell wall mechanical properties to be followed.In unstressed plants, differences in LGR along the root apex were owing to variations in the mechanical properties of the cell walls since P remained constant at 0.5 MPa along the first 10 mm of the root tip. Contrary to expectation, a moderate water stress of 0.15 MPa stimulated root growth despite a small reduction in P to 0.4 MPa. The walls of the expanding cells became looser, allowing enhanced growth in spite of reduced turgor. Examination of LGR showed that these changes occurred uniformly over the whole elongation zone. The advantage to the plant of this is discussed. Higher stresses (0.45 and 0.66 MPa) decreased cell turgor to a greater degree (≤0.3 MPa) and decreased growth rate. At the highest stress (0.66 MPa), P was maximal in cells that were still elongating, resulting in a longitudinal gradient in turgor. In both treatments LGR remained unchanged at the apex of the growing zone. Wall loosening appeared to have occurred in this region. Pine root extension is therefore modulated by changes in cell wall properties, with cell wall loosening resulting in increased growth at moderate stress. It appears that growth under higher stresses is limited by inability to maintain turgor.
Microtubule arrays in maize root cells. Interplay between the cytoskeleton, nuclear organization and post‐mitotic cellular growth patterns
Authors: BALUŠKA F. , BARLOW P. W. , HAUSKRECHT M. , KUBICA Š. , PARKER J. S. , VOLKMANN D. 
Published: April 2006

summaryResults from studies with metabolic inhibitors suggest that, in growing cells of the maize root apex, nuclear metabolism is involved in the organization of the cortical microtubular arrays (CMTs) located at the cell periphery. Nucleus‐derived factors intrinsic to each individual cell are inferred as being responsible for the accomplishment of the MT‐dependent transition from the approximately isodiametric mode of cellular growth, characteristic of the immediate post‐mitotic root region, to the strictly directional cell lengthening in the elongation zone. These hypothetical factors seem to be related to RNA but not DNA synthesis, as indicated by our inhibitor studies. For instance 5‐fluorodeoxyuridine, an inhibitor of DNA synthesis, had little effect on orientation of CMTs, when these were present, and allowed the developmental switch from more or less isodiametric mode of cell growth into highly polarized cell elongation to occur. In contrast, actinomycin D, a specific inhibitor of nuclear metabolism which rapidly halts rRNA synthesis, affected both the polarity and efficacy of postmitotic cell growth and impaired the transversal arrangement of CMTs as well as inducing the appearance of prominent ‘holes’ in their bundled arrays. These latter effects of actinomycin D cannot be simply explained by its indirect effect on translation, through impairment of functional ribosome assembly, as they were visible after only 15 min. Moreover, inhibition of protein synthesis by cycloheximide resulted in a different response. There was rapid and complete loss of the preferred transverse orientation of CMTs and the individual CMTs failed to organize themselves into bundles. Endoplasmic microtubules (EMTs), located more internally between plasma membrane and nucleus, seem to be important for determining nuclear size and chromatin architecture, since whenever EMTs were caused to disintegrate (cold and anti‐MT drug treatments), meristematic nuclei swelled and their chromatin dispersed. By contrast, when EMTs were stabilized and increased in number by taxol, which specifically favours MT polymerization, the nuclei became smaller and the chromatin more condensed. Nevertheless, the mechanisms of these complex interplays between the MT cytoskeleton and the nuclear organization remain unclear.
Effects of elevated CO2, water and nutrients onPicea sitchensis(Bong.) Carr seedlings
Authors: TOWNEND JOHN 
Published: April 2006

summarySitka spruce (Picea sitchensis(Bong.) Carr.) seedlings were grown from seed for one year in naturally lit growth chambers with either ambient or ambient + 250 ppm concentrations of CO2. In the following year the plants were grown in the same CO2treatments for the whole growing season at two concentrations of nutrients and were either well‐watered or subjected to a long‐term, gradually increasing drought.Elevated CO2increased significantly growth in all treatments except the well‐watered, unfertilized treatment. The relative increases in end‐of‐year biomass in the elevated CO2treatment compared with the ambient treatment were: well‐watered, fertilized + 52%, well‐watered, unfertilized +19%, droughted, fertilized+ 44%, and droughted, unfertilized + 49%.Growth analysis revealed that treatment effects on both unit leaf rates and leaf area duration were important in determining the final masses of the plants. Plants growing in elevated CO2had increased relative growth rates in the first half of the growing season but only slightly increased or even slightly decreased relative growth rates in the later part of the growing season in all water × nutrient treatments.Overall there was a significant CO2× water × nutrient interaction on end‐of‐year biomass. A combination of small nutrient concentration and adequate water supply led to the smallest growth response to elevated CO2.
Ozone induction of extensin mRNA in Scots pine, Norway spruce and European beech
Authors: SCHNEIDERBAUER A. , BACK E. , SANDERMANN H. , ERNST D. 
Published: April 2006

summaryFumigation of tree seedlings and saplings with ozone increased the mRNA level of extensin, a hydroxyprolinerich cell wall glycoprotein. European beech (Fagus sylvatica L.), Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) seedlings and saplings of various ages were treated with ozone concentrations from 20 nl l−1 up to 200 nl l−1 for 1 h up to several weeks. A strong increase of extensin transcript levels was detected within a few hours of fumigation. The induction occurred in needles and hypocotyls of Scots pine, needles of Norway spruce and leaves of European beech. Hypocotyls and roots with high levels of constitutive lignification were not induced. The degree of lignification in hypocotyls of equally old pine and spruce seedlings correlated with the degree of ozone‐induced transcription of extensin genes.
Attempted isolation and success in the culturing of a broad spectrum of lichen‐forming and lichenicolous fungi
Authors: CRITTENDEN P. D. , DAVID J. C. , HAWKSWORTH D. L. , CAMPBELL F. S. 
Published: April 2006

summaryIsolation into pure culture was attempted on 1183 species (2238 specimens) of lichen‐forming and lichenicolous fungi from diverse ecosystems and systematic groups (covering 14 ascomycete orders, 77 families and 280 genera), in 20 countries. Four hundred and ninety three species (42%) were successfully isolated either from ascospores (or basidiospores, or conidia) or photobiont‐free fragments from thallus macerates. Of the total number of isolation attempts from ascospores (1609) and thallus fragments (719), 30% and 32% respectively were successful. The reasons for failure to isolate from ascospores were: ascospores did not germinate (43%) > ascospores were not discharged (30%) > ascospores germinated but growth was not sustained (19%) > discharged spores were heavily contaminated (8%). 59% of isolation failures with fragments were due to lack of growth and 41% were due to contamination. The orders from which mycobionts were most readily isolated were the Ostropales (70% of species attempted were isolated), Dothideales (63%), Pertusariales (53%) and Lecanorales (45%); those orders least readily yielding isolates were Vemicariales (10%), Gyalectales (20%), Arthoniales (30%), Lichinales (29%) and Peltigerales (27%). Members of the Lecanorales comprised c. 60% of species collected of which Porpidiaceae (80% of species successfully isolated), Cladoniaceae (69%), Lecideaceae (67%), Rhizocarpaceae (62%), Umbilicartaceae (60%), Ramalinaceae (60%) and Lecanoraceae (54%) were comparatively successful families and Alectoriceae (18%), Catillariaceae (8%), Pannariaceae (8%) Collemataceae (7%), and Micareaceae (6%) were least successful.Of those species containing a cyanobacterium (either as the primary photobiont or in cephalodia), only 22% yielded isolates compared with 46%, and 43%, of lichens containing only a chlorococcoid photobiont or Trentepohlia, respectively. Success was even lower (17%) in species containing a cyanobacterium as the primary photobiont. Among non‐cyanobacterial lichens, isolation of mycobionts was achieved in 56% of fruticose species collected compared with 43% and 40% for crustose/squamulose and foliose taxa respectively. Mycobionts of fruticose lichens cultured particularly readily from fragments, with 56% of green algal species to which this method was applied coming into culture compared to 37% of non‐cyanobacterial foliose species. Lichenicolous fungi cultured less readily, with only 31% of species yielding isolates.In many species viability of ascospores varied between collections. Weather conditions at the time of collection, environmental conditions during transportation, and developmental stage of ascomata of pyrenocarpous lichens might partly explain this variation.
Physiological ecology of cyanobacteria in microbial mats and other communities
Authors: STAL LUCAS J. 
Published: April 2006

summaryIn this review some aspects of the physiological ecology of cyanobacteria are discussed by taking a microbial mat as an example. The majority of microbial mats are built and dominated by cyarsobacteria which are primary producers at the basis of the microbial foodweb in microbial mats. These micro‐scale ecosystems are characterized by steep and fluctuating physico‐chemical gradients of which those of light, oxygen and sulphide are the most conspicuous. Light is strongly attenuated in the sediment, and owing to constant sedimentation, the mat‐forming cyanobacteria have to move upwards towards the light. However, at the sediment surface, light intensity, particularly in the u.v. part of the spectrum, is often deleterious. The gliding movement of the cyanobacteria, with photo‐ and chemotaxis, allows the organism to position itself in a thin layer at optimal conditions. The organic matter produced by cyanobacterial photosynthesis is decomposed by the ruicrobial community. Sulphate‐reducing bacteria are important in the end‐oxidation of the organic matter. These organisms are obligate anaerobes and produce sulphide. Gradients of sulphide and oxygen move up and down in the sediment as a response to diurnal variations of light intensity. Cyanobacteria, therefore, are sometimes exposed to large concentrations of the extremely toxic sulphide. Some species are capable of sulphide‐dependent anoxygenic photosynthesis. Other cyanobacteria show increased rates of oxygenic photosynthesis in the presence of sulphide and have mechanisms to oxidize sulphide while avoiding sulphide toxicity. Iron might play an important role in this process. Under anoxic conditions in the dark, mat‐forming cyanobacteria switch to fermentative metabolism. Many species are also capable of fermentative reduction of elemental sulphur to sulphide. The gradients of sulphide and oxygen are of particular importance for nitrogen fixation. Very few microbial mats are formed by heterocystous cyanobacteria, which are best adapted to diazntrophic growth. However, these organisms probably cannot tolerate greater concentrations of sulphide or anoxic conditions or both. Under such conditions non‐heterocystous cyanobacteria become dominant as diazotrophs. These organisms avoid conditions of oxygen supersaturation. In the ecosystem, nitrogen fixation and photosynthesis might be separated temporally as well as spatially. In addition, non‐heterocystous diazotrophic cyanobacteria have mechanisms at the subcellular level to protect the oxygen‐sensitive nitrogenase from inaction.

CONTENTS

Summary
1

I.
Introduction
2

II.
Microbial mats
3

III.
Cyanobacteria in light gradients
7

IV.
Dark metabolism
10

V.
Interactions with sulphide
13

VI.
Nitrogen fixation
16

VII.
References
28