bluuebunny/crossref_metadata_2025_split huggingface dataset:
A comparison of the extracellular enzyme activities of two ectomycorrhizal and a leaf‐saprotrophic basidiomycete colonizing beech leaf litter
Authors: COLPAERT JAN V. , VAN LAERE ANDRÉ 
Published: April 2006

summaryActivities of extracellular enzymes were determined in beech (Fagus sylvatica L.) leaf litter colonized by the litter decomposer Lepista nuda (Bull.: Fr.) Cooke or by vegetative mycelium from the mycorrhizal fungi Thelephora terrestris Ehrh.: Fr. or Suillus bovinus (L.: Fr.) O. Kuntze. Organic matter (OM) was buried for up to 6 months in plant containers in which mycorrhizal or non‐mycorrhizal Pinus sylvestris L. seedlings were cultivated at a low rate of nutrient addition. After different periods of colonization the activities of phosphomonoesterase and protease, two enzymes involved in nitrogen and phosphorus mobilization, were determined in colonized and uncolonized litter. The activities of cellulase, β‐xylosidase, β‐glucosidase and polyphenol oxidase were investigated as indicators of the decomposition capacity of the fungi in the litter. Low activities of all enzymes tested were found in the uncolonized beech leaves. Phosphomonoesterase activity was high in litter colonized with L. nuda or S. bovinus, and was intermediate in the T. terrestris treatment. For all other enzymes the activities in the OM inoculated with the white‐rot litter decomposer were considerably larger than those detected in litter colonized by ectomycorrhizal basidiomycetes. Cellulase activity was low in the control as well as in the mycorrhizal treatments. β‐Xylosidase and β‐glucosidase were detected in the litter with mycorrhizal mycelium, whereas polyphenol oxidase activity was only clearly increased in the S. bovinus treatment. These results demonstrate the low lignocellulase activity of both mycorrhizal fungi. This feature reduces the capacity of the mycorrhizal fungi to exploit fresh beech leaf litter, whose endogenous nitrogen is associated with or shielded by refractory compounds. The results are discussed in relation to the role of ectomycorrhizal fungi in nutrient cycling processes m temperate forest ecosystems.
Sulphite and pH effects on CO2 evolution by fungi growing on decomposing coniferous needles
Authors: DURSUN S. , FRANKLAND JULIET C. , BODDY LYNNE , INESON P. 
Published: April 2006

summaryThe relative sensitivities of Mycena galopus (Pers.) Kummer, Phoma exigua (Desm.), Cladosporium clodosporioides (Fres.) de Vries and Aureobasidium pullulans (de Bary) Arnaud to low concentrations (12.5–100.0 μM) of sulphite (SO2−3) when growing on decomposing needles of Picea sitchensis (Bongard) Carrière (Sitka spruce) and Pinus sylvestris L. (Scots pine) were assessed. Carbon dioxide evolution from the decomposing needles was strongly inhibited by SO32− at pH 3.0–4.5 P. exigua was the most sensitive of the species tested in the mycelial state, and C. cladosporioides was the most sensitive species tested as spores. Mycelium was consistently less sensitive than spores. The inhibitory effect of SO32− on CO2, evolution was increased by increasing the SO32− concentration or decreasing the pH. The concentrations shown to exert toxicity were similar to those which have been measured in rainfall in the UK, and the results provide evidence that SO32− can be toxic to litter fungi at environmentally realistic concentrations.
Effect of phosphorus deficiency on growth angle of basal roots in Phaseolus vulgaris
Authors: BONSER AMY M. , LYNCH JONATHAN , SNAPP SIEGLINDE 
Published: April 2006

summaryRoot architectural plasticity might be an important factor in the acquisition by plants of immobile nutrients such as phosphorus (P). In this study, we examined the effect of P availability on the orientation of basal roots with respect to gravity, and thereby on the growth angle of these roots of common bean (Phaseolus vulgaris L.). In one set of studies the growth angle of basal roots of bean seedlings was measured over time. Sixteen bean genotypes were examined; six showed a decrease in root orientation with respect to gravity m low P media, one increased orientation, and nine showed no difference within 5 d of basal root emergenece. Bean taproots also showed decreased root orientation with respect to gravity in law P. Growth angle after 5 d was correlated with field performance of contrasting genotypes to low P tropical soils. Mineral deficiencies other than P did not cause changes in root angle. In a. split pouch system that provided high or low P solution to different parts of the root system, the decrease in root angle in low P was found to be a response to globat P availability, and not local to the portion of the root system in low P, Effects of P availability on root angle were associated with reduced shoot P concentration, but preceded effects on plant biomass accumulation and leaf area expansion. Results from growth pouches for genotype G 19833 were confirmed using a solid‐phase buffered sand‐culture system supplying P at three levels. Pea (Pisum sativum), soybean (Glycine max Williams), chickpea Cicer arietinum), lima bean (Phaseolus lunatus), and lentil (Lens culinaris) were grown with and without P; soybean and pea also showed decreased basal rout angles m low P.
Nitrite assimilation by the yeast Candida nitratophila
Authors: AL KUBISI ADNAN , ALI ABID H. , HIPKIN CHARLES R. 
Published: April 2006

summaryNitrite uptake in the nitrate‐assimilating yeast, Candida nitratophila, was inhibited completely by addition of nitrate or ammonium to cultures at pH 8.0). Nitrite assimilation in these cultures was also completely dependent on the availability of a suitable carbon source (glucose), In cultures at pH 5.0, neither nitrate nor ammonium inhibited nitrite uptake completely. In these cultures, some nitrite was assimilated in the absence of a carbon source. Carbon‐deficient cultures at pH 5.0 were able to reduce nitrite to ammonium but excreted this ammonium without further assimilation, Evidence for the uptake of nitrite by passive diffusion and by active transport via the nitrate uptake system is discussed.
Effects of elevated CO2, nitrogen form and concentration on growth and photosynthesis of a fast‐ and slow‐growing grass
Authors: BOWLER JOHN M. , PRESS MALCOLM C. 
Published: April 2006

summaryGrowth and photosynthesis of Agrostis capillaris L. and Nardus stricta L. were measured for plants grown under ambient and elevated concentrations of CO2(340 and 550 μl CO2 l−1 respectively) and a range of nitrogen concentrations (0.01, 0.1, 1 and 5 mg N l−1) supplied as either ammonium sulphate or sodium nitrate. After 42 d of growth for A. capillaris and 49 d of growth for N. stricta, the higher nitrogen concentrations resulted in stimulation of growth. The form of nitrogen did not affect the total dry weight attained by A. capillaris. However, ammonium‐grown N. stricta attained a greater total dry weight than did nitrate‐grown plants. Nitrogen form influenced leaf area ratio, which was greater in nitrate‐grown A. capillaris and in ammonium‐grown N. stricta. At the two lowest nitrogen concentrations there was no effect of elevated CO2 on total dry weight in either species, whilst at the two highest nitrogen concentrations positive growth responses to elevated C02 were observed. Photosynthetic capacity and carboxylation efficiency were lower in plants grown in elevated CO2 at the two lowest nitrogen concentrations, and were associated with greater leaf soluble carbohydrate content and lower foliar nitrogen concentrations. By contrast, the CO2 treatment did not affect these parameters at the two highest nitrogen concentrations employed.
Regional and local patterns in the spatial distribution of the flower‐infecting smut fungus Sporisorium amphilophis in natural populations of its host Bothriochloa macra
Authors: GARCÍA‐GUZMÁN GRACIELA , BURDON JEREMY J. , ASH JULIAN E. , CUNNINGHAM ROSS B. 
Published: April 2006

summaryRegional variation in the incidence of the systemic floral‐smut fungus Sparisorium amphilophis (Syd.) Langdon & Fullerton an the perennial grass Bothriochloa macra (Steud.) S. T. Blake was investigated through three surveys over a 12 yr period (1981–93). In all three surveys a marked north‐south trend in percentage of infection was detected with a greater proportion of plants in northerly populations being infected than in populations located to the south. The incidence of disease in populations was negatively correlated with the frequency of days with temperatures <0°C in winter. Detailed exploration of local variation in a subset of five populations showed that the incidence of S. amphilophis was density‐dependent and was greater in the edge areas of host populations than in the less disturbed core areas. Smut prevented seed production and negatively affected different aspects of the morphology of the plants, such as the height and basal diameter. Infection also significantly increased the number of inflorescences per plant. These field results were complemented by glasshouse‐based competition experiments which indicated that, despite causing reductions in size, S. amphilophis only affected the competitive ability of infected plants grown under sub‐optimal conditions. The results of this study indicate that an interplay between physical and biotic aspects of the environment determines regional and local levels of disease.
Influence of xylem vascular architecture on the translocation of phosphorus from nodal roots in a genotype of Trifolium repens during undisturbed growth
Authors: HAY M. J. M. , HAMILTON N. R. SACKVILLE 
Published: April 2006

summaryOur objective was to establish whether the xylem vascular connections (architecture) of a genotype of Trifolium repens L. had implications for the intraplant allocation of recently assimilated phosphorus (P). One nodal root of each plan! was isolated and fed 32P‐labelled nutrient solution for 24 h. The fed root was either on the parent axis (11–12 nodes proximal CO the apex) or on a branch at the third or fourth node along the branch when counting from the junction with the parent stolon. Allocation patterns were obtained by dissecting plants and assaying each dissected component for 32P.Under conditions of undisturbed growth in a controlled environment xylem architecture was found to have an important influence on the intraplant distribution of 32P from nodal roots. Allocation patterns of 32P were consistent with those predicted from knowledge of the xylem vascular architecture of the genotype and a predominantly acropetal direction of the transpiration stream. For instance, very little 32P (< 1 % of exported 32P from the fed root) was found in branches on the opposite side of the stolon to the fed root, and the strong acropetal direction of the transpiration stream resulted in little allocation of 32P to leaves that had traces that arose from axial bundles at positions proximal to that of the fed root (the leaf subtending the fed root and the next distal leaf had low 32P content), to all plant organs proximal to the fed root (< 6%) and to all other roots (<4%).The high allocation of 32P to the branch arising at the same node as the fed root (64%) reflects the numerous links that the‐ fed root has to vascular bundles in the branch (3–6, of which two are axial bundles) against the single connection it has to the adjacent lower axial bundle in the parent stolon. Allocation of 32P to the leaf and axillary bud at each node along the branch strongly favoured nodes on the adaxial side, a result consistent with the fact that the root connections are to the upper and lower axial bundles on the adaxial side of the branch. Allocation to a particular node along the branch was also influenced by its nodal position relative to the fed root and the sink strength of its tissues for the transpiration stream.
Monoclonal antibodies as tools to quantify mycelium of aquatic hyphomycetes
Authors: BERMINGHAM S. , MALTBY L. , DEWEY F. M. 
Published: April 2006

summaryQuantitative ELISAs have been developed to determine the biomass of two aquatic hyphomycetes in natural mixed assemblages. These assays employ a species specific rat monoclonal antibody (MAb) raised to Alatospora acuminata and a genus‐specific murine MAb raised to Tetracladium marchalianum. The respective antigens are produced constitutively and their production is not affected by a range‐ of culture conditions. The MAbs can also be used to study the spatial distribution of these fungi using Immunofluorescence. Both antibodies recognize carbohydrate epitopes and belong to the immunoglobulin class IgM. The potential applications of these immunoassays are discussed.
Development of water‐conducting cells in the antipodal liverwort Symphyogyna brasiliensis (Metzgeriales)
Authors: LIGRONE ROBERTO , DUCKETT JEFFREY G. 
Published: April 2006

summaryThe thallus of the metzgerialean liverwort Symphyogyna brasiliensis Nets contains a strand of dead thick‐walled tells with helicoidally‐arranged pits that arc presumably involved in water transport. During the first phase of differentiation these cells undergo a 13–16‐fold elongation while remaining thin‐walled and almost unchanged in diameter. During subsequent maturation the walls become strongly thickened by deposition of highly electron‐opaque material on extraplasmodesmal areas and of transparent material forming collars around plasmodesmata. Whilst the growing wall shows an ordered microribrillar texture and is strongly reactive to PATAg staining for carbohydrates, the material associated with plasmodesmata is amorphous and PATAg‐negative. A dense cortical array of microtobules (MTs) overlies the growing wall except in proximity to plasmodesmata, which are closely associated with tubular endoplasmic reticulum (ER). During cellular maturation plasmodesmata undergo extensive secondary elongation by incorporation of cortical ER supposedly continuous with desmotubules. Quantitative analysis of plasmodesmal frequencies in relation to cellular elongation and wall thickness indicates that there is no de novo formation of plasmodesmata. Cortical MTs, wall microfibrils and secondarily‐modified plasmodesmata are consistently co‐aligned, all forming helices of about 45°. During maturation the Golgi apparatus proliferates and a vast number of vesicles containing PATAg‐positive material are produced from a membrane domain interpreted as trans Golgi network, whilst PATAg‐negative vesicles are formed along the fenestrated margins of C& and media) dictyosomal cisternae. Exocytosis of PATAg‐positive vesicles is confined to extraplasmodesmal areas. In ageing cells abundant fibrillar material, also positive to PATAg‐test, accumulates within pleomorphic membrane‐bounded tubules. Final cytoplasmic dissolution involves the lysis of all cellular membranes and the liberation of the membrane‐bounded fibrillar material, that is subsequently deposited onto the walls. The eventual dissolution of the plugs of amorphous electron‐transport material results in the formation of open pits. Similarities in the cytological mechanisms underlying pore development in water‐conducting cells of Symphyogyna and in the sieve elements of angiosperms are discussed.
Photosynthetic responses of a moss, Tortula ruralis, ssp. ruralis, and the lichens Cladonia convoluta and C. furcata to water deficit and short periods of desiccation, and their ecophysiological significance: a baseline study at present‐day CO2 concentration
Authors: TUBA ZOLTAN , CSINTALAN ZSOLT , PROCTOR MICHAEL C. F. 
Published: April 2006

summaryWe report the changes in CO2 assimilation, potential photochemical activity (as measured by slow fluorescence), photosynthetic pigment concentrations, and dark respiration of two desiccation‐tolerant (DT) lichens (Cladonia convoluta (Lam.) P. Cout. and C. furcata (Huds.) Schrad.), and a DT moss (Tortula ruralis (Hedw.) Gaertn. ssp. ruralis) during slow drying, and on rehydration following a 12 h period of desiccation. Initially there was a two to fourfold increase in net CO., assimilation due to reduction of CO2‐diffusion resistance by elimination of excess water. Optimum water content for photosynthesis was 100–150 % of dry mass (DM) in C. convoluta, c. 100 % DM in C. furcata, and 120–200 % DM in T. ruralis. The intensity of maximum and steady‐state slow fluorescence showed little change above water contents of 56%, DM in the lichens and 73 % DM in T. ruralis (corresponding to c. 30–40 % cell relative water content), but fell sharply at lower water content. The variable duorophyll‐fluorescence decrease ratio (Rfd) at 690 nm peaked at 56 % DM water content in the two lichens, and at 45% DM in T. ruralis. Photochemical activity ceased at the same point in the experiments as CO, assimilation; dark respiration ceased only when desiccation was complete. In all three species, the photosynthetic apparatus remained in a fully and quickly recoverable state. Chlorophyll and carotenoid concentrations remained substantially unaltered throughout. On rehydration, chlorophyll fluorescence parameters returned within 30 min to pre‐desiccation levels, and photosynthesis recovered fully and rapidly (< 1 h). All three species attained a positive carbon balance within 20 min of re‐moistening, in spite of high rates of dark respiration. The results confirm the significance of extracellularly‐stored water to poikilohydric DT lichens and bryophytes. The measurements, in conjunction with published data on the full‐turgor water content of similar mosses and lichens, show that the cell‐physiological response of photosynthesis to water deficit is not greatly different from that of either normal or DT vascular plants. Small plant size and small cell volume in DT lichens and mosses, together with rapid recovery of photosynthesis after desiccation, allow the plants to utilize the small amounts of intermittently available water from brief showers or dew.
Structure of fructan polymers from tuberous roots of Gomphrena macrocephala (Amaranthaceae) from the cerrado
Authors: SHIOMI NORIO , ONODERA SHUICHI , VIEIRA CANDIDA C. J. , FIGUEIREDO‐RIBEIRO RITA C. L. 
Published: April 2006

summaryTwo fructo‐polysaccharides, FP‐I and FP‐II, were separated from a soluble extract from tuberous roots of Gomphrena macrocephala St.‐Hil. by gel permeation chromatography on Toyopearl HW‐40S. FP‐I and FP‐II were mixtures of saccharides with a wide‐ranging degree of polymerization; their acid hydrolysis products were fructose and glucose. The ratios of fructose to glucose in the hydrolysates of FP‐I and FP‐II were 38 and 60, respectively. The average molecular weights of FP‐I and FP‐II were estimated to be 5500 and 10000 respectively, by gel permeation HPLC. The structural confirmation of FP‐I and FP‐II was made by 13C‐NMR analysis. Intense signals corresponding to carbon‐1 (C1), C2, C3, C4, C5 and C6 of fructose residues in FP‐I and FP‐II were observed at δ 60.60, 104.93, 76.99, 75.91, 81.02 and 64.11, respectively. These chemical shifts coincided with those of timothy and bacterial levans. The less intense resonances were tentatively assigned to carbons of terminal fructosyl residues and a fructosyl residue linked to a glucose residue by a β‐2,1 bond in FP‐I and FP‐II. Also, weak signals attributed to carbons of the glucose residue in both polysaccharides were separated from those of other glycosyl residues. These findings were supported by GLC analysis of methanolysate from permethylated FP‐I and FP‐II. Thus FP‐I and FP‐II comprise fructose residues with β‐2,6 linkages, and a terminal glucose bound with fructose residues at position C1, although both polysaccharides possibly contained a non‐terminal glucose residue in the molecule.
Microcystin‐LR inhibits photosynthesis ofPhaseolus vulgarisprimary leaves: implications for current spray irrigation practice
Authors: ABE TOSHIHIKO , LAWSON TRACY , WEYERS JONATHAN D. B. , CODD GEOFFREY A. 
Published: April 2006

summaryPhotosynthesis ofPhaseolus vulgarisL. leaves was measured after treatment with microcystin‐LR (MC‐LR), a potent cyanobacterial toxin and inhibitor of protein phosphatases 1 and 2A. The net photosynthetic rate fell by over 50% within 8 h of dipping leaves in MC‐LR solution. This inhibitory effect was observed when leaves were treated once with concentrations above 10−2mol m−3. At 10−2mol m−3, the inhibition caused by MC‐LR was transient, and net photosynthesis rates essentially recovered after 5 d, whereas at 10−1mol m−3, the net photosynthesis rate in treated leaves was still 42% of controls after 8 d. Necrosis was observed at the higher concentration, but not usually below 10−2mol m−3. Analysis of net photosynthetic rate as a function of internal CO2concentration and photosynthetically active photon flux density indicated that both the CO2‐saturated rate of photosynthesis and the carboxylation efficiency were lowered when MC‐LR‐treated leaves were exposed to photosynthetically‐saturating light. When the leaves were exposed to 2.0 × 10−5mol m−3MC‐LR solution repeatedly, the photosynthetic rate was significantly reduced after 7 d, suggesting that intermittent exposure ofP. vulgarisleaves to low concentrations of MC‐LR brings about an effect on photosynthesis more inhibitory than that of a single exposure to high concentrations of MC‐LR. These results indicate that relatively low concentrations of MC‐LR cause damage to the photosynthetic apparatus ofP. vulgaris in situ.We discuss the significance of these findings in relation to current spray irrigation practice for crop plants involving the use 6f water containing cyanobacterial blooms and microcystins.
Ultrastructure of the interaction between Fusarium oxysporum f. sp. lycopersici and cultured tomato mutant cells selected for altered response to the pathogen
Authors: MORASSI BONZI LAURA , ADELE PANCANI MARIA , PAOLETTI CINZIA , GABBRIELLI ROBERTO , STORTI EMANUELA , BUIATTI MARCELLO 
Published: April 2006

summaryTomato cell clones selected for high and low (F+ and F−) response to heat‐released cell wall components from Fusarium oxysporum f. sp. lycopersici were analysed ultrastructurally with particular regard to cell wall and membrane modifications in a synchronous dual culture in vitro system which avoided direct contact between the two partners of the interaction. Constitutive differences in cell shape were observed between F+, F− and parental cultivar cells by TEM and SEM. Quantitative morphological analyses, and biochemical determinations showed differences in cell wall thickness and polysaccharide content between cells of the F+ and F− clones. A temporal study revealed differences between the cell clones in (1) the rate of resistance to degradation by fungal polysaccharide hydrolytic enzymes, (2) protoplast destruction, (3) formation of paramural bodies, (4) cell wall appositions (papillae), and (5) mitochondrial alterations. The data are discussed with respect to a possible correlation between cell wall structure and the course of events during the host‐parasite interaction on the one hand and, on the other, active responses to the pathogen as suggested by the literature.