bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lichen physiology and air pollution
Authors: VON ARB CHRISTOPH , MUELLER CHRISTINE , AMMANN KLAUS , BRUNOLD CHRISTIAN 
Published: April 2006

SUMMARYSamples of the lichen Parmelia sulcata Taylor were collected in the vicinity of 17 air pollution monitoring stations in the northern part of Switzerland and its bordering area. Net photosynthesis, dark respiration, and the content of [35S]‐sulphate and [35S]‐protein after cultivation with 35SO42−, as well as the chlorophyll and protein contents were measured. Mean values of dark respiration and protein content were not significantly different in the plant material from the various locations. Most of the mean values of net photosynthesis differed less than the average standard deviation. The rates of sulphate uptake and protein synthesis were lowest and chlorophyll content was highest at the most polluted sites. The values differed by a factor of 3.5‐7 between the various locations. Multiple regression analysis gave a linear correlation between the three physiological parameters [35S]‐sulphate, [35S]‐protein and chlorophyll content and a combination of the annual mean concentrations of the air pollutants NO, NO2, SO2 and O3. The highest multiple correlation coefficient (R2) was estimated for chlorophyll (0‐84). Its linear correlation coefficient (r) with NO2 alone was 0.91, and with SO2 alone 0.85.
Response of radish to multiple stresses
Authors: PELL E. J. , WINNER W. E. , VINTEN‐JOHANSEN C. , MOONEY H. A. 
Published: April 2006

SUMMARYExperiments were conducted to determine the impact of nitrogen and ozone (O3) stress on the growth of domestic radish Raphanus sativus L. cv. Cherry Belle. Plants were grown in field chambers with sub‐, optimal and supra‐optimal levels of nitrogenous fertilizer. Chamber air was either charcoal‐filtered, or supplemented with one of two levels of O3. The highest O3 treatment resulted in significant reduction in weight of hypocotyls and roots while elevated nitrogen treatments resulted in increased weight of all plant parts. Ozone did not affect the weight of plant foliage at any nitrogen level. Plants grown with lower levels of nitrogen had less leaf biomass but the tissue accounted for a greater percentage total weight than did the foliage of higher nitrogen treatments. Relative growth rate of whole plants was not affected by O3 or nitrogen treatments reflecting compensation in response to both stresses. Ozone‐induced depression in biomass was observed in O3‐treated plants grown with higher nitrogen supply but not in those grown with limiting nitrogen. This observation could reflect compensation at the lower levels of nitrogen supply or inability to detect changes in biomass due to reduced weights of plants grown at the lowest nitrogen supply. The dry weight ratio of sink organs (hypocotyl plus root)/shoot was significantly correlated with the total non‐structural carbohydrate (TNC) content of these organs, regardless of treatment. Initially, O3 induced a significant decrease and nitrogen an increase in percent TNC of sink organs. At later sampling times, plants adjusted to stress as effects on percent TNC were no longer evident.
A new method which gives an objective measure of colonization of roots by vesicular—arbuscular mycorrhizal fungi
Authors: McGONIGLE T. P. , MILLER M. H. , EVANS D. G. , FAIRCHILD G. L. , SWAN J. A. 
Published: April 2006

SUMMARYPreviously described methods to quantify the proportion of root length colonized by vesicular‐arbuscular (VA) mycorrhizal fungi are reviewed. It is argued that these methods give observer‐dependent measures of colonization which cannot be used to compare, quantitatively, roots examined by different researchers. A modified method is described here to estimate VA mycorrhizal colonization on an objective scale of measurement, involving inspection of intersections between the microscope eyepiece crosshair and roots at magnification × 200; it is referred to as the magnified intersections method. Whether the vertical eyepiece crosshair crosses one or more arbuscules is noted at each intersection. The estimate of colonization is the proportion of root length containing arbuscules, called the arbuscular colonization (AC). The magnified intersections method also determines the proportion of root length containing vesicles, the vesicular colonization (VC), and the proportion of root length containing hyphae, the hyphal colonization (HC). However, VC and HC should be interpreted with caution because vesicles and hyphae, unlike arbuscules, can be produced in roots by non‐mycorrhizal fungi.
The effect of soil water potential on seed germination of some British plants
Authors: EVANS CERI E. , ETHERINGTON JOHN R. 
Published: April 2006

SUMMARY‘Seeds’ of 15 species collected from a range of habitats contrasting in soil water status were germinated in soils of known matric potentials ranging from near field capacity to the permanent wilting potential (– 0.05, –0.5, –1.0 and –1.5 MPa). Germination was very sensitive to soil water potential and species responded in various ways. Some showed germination responses which correlated with the soil water status of their native habitat: none of the wetland species studied could germinate to any great extent at low soil water potentials; in contrast some species associated with drier habitats achieved high levels of germination in soils as dry as –1.0 MPa (and –1.5 MPa for one ruderal species). However, other species from drier habitats failed to germinate at low soil water potentials, and it is suggested that this may be a mechanism to avoid exposing the seedling to an unfavourable environment.
Occurrence of soluble carbohydrates on the phylloplane of maize (Zea mays L.): variations in relation to leaf heterogeneity and position on the plant
Authors: FIALA V. , GLAD C. , MARTIN M. , JOLIVET E. , DERRIDJ S. 
Published: April 2006

summaryTwo techniques for collection of water‐soluble substances, particularly carbohydrates, from the leaf surfaces (phylloplane) of maize (Zea mays L.) were compared in order to explain the oviposition preference of the European corn borer.By dipping the leaves in water, smaller amounts of substances were obtained than by spraying water. The total amounts of three sugars (glucose, fructose and sucrose) collected from maize phylloplane ranged from 0.6 to 3.6 mg m−2 of leaf surface.The quantities of these substances varied with the variety of maize, with leaf position, and with the part of the leaf. Sugar ratios on the phylloplane were quite different from those observed within the leaf.
Effects of liming on ectomycorrhizal fungi infecting Pinus sylvestris L.
Authors: ERLAND SUSANNE , SÖDERSTRÖM BENGT 
Published: April 2006

summary Pinus sylvestris L. seedlings were grown in the laboratory in a forest humus which had been treated with different levels of CaO to give a soil pH gradient from 4 to 7. After 12 and 15 wk the resulting ectomycorrhizal infection was classified according to macroscopical morphology. The uniformity of the infection types distinguished was evaluated by isolating the fungi from the root tips and infecting seedlings with the isolates obtained. The isolation method was improved by using a medium containing benomyl and chlortetracyclin and by isolating from very small particles. For some mycorrhizal types the fungus was successfully isolated from 80% of the plated root particles.The number of root tips that became mycorrhizal increased from 70% at pH 4 to nearly 100% around pH 5. Thereafter it decreased linearly to reach a minimum of slightly less than 40% at pH 7.5. Five different mycorrhizal types could be distinguished. They occurred with different abundance, distribution and pH optima. They were present throughout the entire pH range, except for a yellow type, identified as Piloderma croceum Erikss. & Hjortst., which was not found at values higher than 6–2. There was no great differences between infections on plants harvested after 12 and 15 wk. Seedling growth was constant to pH 5 then it increased up to about pH 7, at higher pH values growth declined.
Effect of nodulation, nitrogen fixation and CO2 enrichment on the physiology, growth and dry mass allocation of seedlings of Alnus rubra Bong.
Authors: ARNONE JOHN A. , GORDON JOHN C. 
Published: April 2006

SUMMARYInoculated and uninoculated Alnus rubra Bong, seedlings were grown for 47 days in atmospheres containing ambient (350 μ1 CO2 1−1) and elevated (650 μl CO2 1−1) levels of CO2, with and without combined nitrogen (20 mg 1−1) supplied as ammonium nitrate. Five plants from each treatment were harvested 15, 30, and 47 days after exposure to CO2 treatments began. Evidence for the presence of a positive feedback loop between nitrogen fixation and photosynthesis was observed in nodulated plants growing at elevated CO2. These plants had greater whole‐plant photosynthesis and nitrogenase activity, leaf area and nitrogen content, as well as nodule and plant dry mass, relative to nodulated plants grown at ambient CO2 and non‐nodulated plants grown at both CO2 levels. This feedback may be an important way in which the potential carbon drain of nitrogen fixation on the host plant could be compensated; increased nitrogen availability resulting in stimulated leaf area growth and whole‐plant photosynthesis. The relative amount of dry mass allocated below ground decreased for all seedlings over time, and the amount allocated above ground increased. This shift in allocation occurred slowly and at a constant rate in non‐nodulated plants and more rapidly and abruptly when plants were nodulated. The proportion of dry mass allocated below ground was consistently greater in non‐nodulated plants. Dry mass allocation to the stem was increased when combined nitrogen was applied and was greatest in nodulated plants grown at high CO2. Dry mass partitioning among other organs was not directly affected by nodulation, CO2 enrichment, or other treatment interactions.
Polyamine metabolism in ‘green‐islands’ on powdery mildew‐infected barley leaves: possible interactions with senescence
Authors: COGHLAN S. E. , WALTERS D. R. 
Published: April 2006

SUMMARYPolyamine metabolism, lipoxygenase and catalase activities and ethylene production were examined in green‐islands induced to form on detached barley leaves infected with the powdery mildew fungus, Erysiphe graminis f. sp. hordei Marchal. Several‐fold increases in free polyamines were detected in green‐islands, which could not be accounted for by changes in polyamine biosynthetic and degradative enzymes: a small increase in ornithine decarboxylase (ODC) activity, greatly decreased arginine decarboxylase (ADC) activity, virtually unchanged activity of S‐adenosylmethionine decarboxylase (AdoMetDC) and greatly increased polyamine oxidase (PAO) activity. Changes in conjugated forms of polyamines suggest that elevated free polyamine concentrations might result from reductions in this pool. Green‐island tissues displayed a reduced activity of lipoxygenase, unchanged catalase activity and a greatly lowered rate of ethylene production. Chlorophyll concentration and rates of photosynthesis and dark respiration were slightly increased in these tissues.In senescing regions of infected leaves, there was a small increase in free putrescine and spermine and a decrease in spermidine concentration, while concentrations of conjugated polyamines were substantially reduced. This was accompanied by an overall decrease in ODC and ADC activities and an increased activity of both AdoMetDC and PAO. These regions exhibited lowered lipoxygenase activity, greatly enhanced catalase activity and reduced rates of ethylene production. In addition, senescing regions exhibited a substantial reduction in chlorophyll concentration and the rate of photosynthesis, although dark respiration was similar to control values.These results support the view that green‐islands represent areas of the infected leaf where senescence is retarded, biosynthetic activity is retained and in which polyamines may play an important role. On the other hand, although polyamine concentrations were reduced in senescing areas, other changes occurring there suggest that some functional integrity is maintained in that tissue.
Nitrogenase in Frankia from root nodules of Alnus incana (L.) Moench: immunolocalization of the Fe‐ and MoFe‐proteins during vesicle differentiation
Authors: HUSS‐DANELL KERSTIN , BERGMAN BIRGITTA 
Published: April 2006

SUMMARYThe localization of nitrogenase was studied in root nodules of Alnus incana (L.) Moench in symbiosis with a local source of Frankia. Nodules were fixed in glutaraldehyde and embedded in Epon or LR White. Ultrathin sections were examined by TEM after incubation with antisera against nitrogenase and gold‐conjugated secondary antibodies. Antisera against dinitrogenase reductase (Fe‐protein) from Rhodospirillum rubrum and dinitrogenase (MoFe‐protein) from Azotobacter vinelandii were used. Immunogold label density in hyphae and in spores of Frankia was low and similar to that of plant tissue. Very young vesicles without septa showed a label density of Fe‐protein similar to that of hyphae, while young vesicles with a few, usually non‐transversing, septa had a significant but still low density of label. Mature vesicles, highly compartmentalised due to transversing septa, contained statistically significantly more Fe‐protein label than all other cell types. Old degenerating vesicles always contained nitrogenase, about half as much as that of mature vesicles but often more than young vesicles. Similarly, MoFe label was not detected in hyphae, appeared in young but was greatest in mature vesicles. It is apparent that differentiation of vesicles reaches a certain stage of development prior to the onset of nitrogenase synthesis.
The control of ozone uptake by Picea abies (L.) Karst. and P. sitchensis (Bong.) Carr. during drought and interacting effects on shoot water relations
Authors: DOBSON M. C. , TAYLOR GAIL , FREER‐SMITH P. H. 
Published: April 2006

SUMMARYExposure to O3 alone has not yet been shown to reproduce the symptoms of the various types of spruce decline which have been identified in Europe. However, there is increasing evidence that this pollutant has physiological effects which interact with those of other environmental factors in ways which may be important in determining tree condition and growth. The effects of O3 episodes and drought on O3 uptake, gas exchange and water relations of Picea abies (L.) Karst. and P. sitchensis (Bong.) Carr. were investigated in two experiments. In the first a rapidly drying soil mixture was used, and seedlings of P. abies were exposed to short (2 h) daily episodes of O3 at 80 nl 1−1 on each day of a 5 d drought. Photosynthesis (A) and stomatal conductance (gs) were significantly decreased (P= 0.01) by water deficit and as a consequence, uptake of O3 by the plants was also significantly decreased. Exposure to O3 did not affect A or gs for this species. In the second experiment a soil mixture designed to give a slower development of water deficit was used and 1 + 1 transplants of P. sitchensis were exposed to a single O3 episode (up to 100 nl 1−1 for 3 h) after water had been withheld for 7 or 14 d. Hofler diagrams showed that mild water deficits did not affect shoot water relations. However, O3 significantly increased solute potential (Ψs) after 7 d of drought, an effect which was lost after 14 d of drought. Flux of O3 to the watered plants was greater than to the unwatered plants at all concentrations, the effect being more marked at higher concentrations. This effect was partly attributable to the greater stomatal conductances recorded for the well watered plants, but was also partly due to stomatal opening caused by O3, an effect which was diminished or reversed for unwatered plants.
A biophysical study of abscisic acid interaction with membrane phospholipid components
Authors: LESHEM YA'ACOV Y. , COJOCARU MIRIAM , MARGEL SHLOMO , EL‐ANI DALIA , LANDAU EHUD M. 
Published: April 2006

SUMMARYMolecular area/surface pressure Langmuir isotherms of amphiphilic dipalmitoylphosphatidylcholine (DPPC) monolayers indicated that abscisic acid (ABA) has a marked rigidifying effect, expressed as reduction of molecular area and increase of monolayer collapse point. Moreover, ABA markedly increased aqueous droplet hydrophobicity, as indicated by a concentration‐dependent increase of contact angle when placed on a hydrocarbon chain surface; no such effects were obtained on either amphiphilic or octadecyltrichlorosilane surfaces. A combination of TLC and mass spectometry revealed the presence of DPPC in Vicia faba and Commelina communis guard‐cell protoplast membranes. ABA also increased plasma membrane rigidity as evidenced by probing with lipid specific membrane probes, namely diphenylhexatriene and its trimethyl derivative. Regarded together the results suggest a specific site of ABA binding to DPPC. The linkage between senescence and stomatal closure is discussed in the light of the new data presented here. It is suggested that DPPC in guard‐cell membranes may have a physical role in preventing collapse and/or bursting. In this connection an analogy is drawn with pulmonary mechanisms.
Ionic control of intracellular and extracellular Cd uptake by the moss Rhytidiadelphus squarrosus (Hedw.) Warnst
Authors: WELLS J. M. , BROWN D. H. 
Published: April 2006

SUMMARYThe effects of K, Ca, Mg and H ions on the kinetics of Cd uptake by the moss Rhytidiadelphus squarrosus (Hedw.) Warnst were investigated. The affinity of extracellular exchange sites for these ions decreased in the order Cd, H > Ca > Mg ≫ K and there were competitive interactions between ions. The affinity of the intracellular Cd transport site for these ions decreased in the order Ca > Cd > Mg ≫ K. Calcium was shown to be competitive and Mg a non‐competitive inhibitor of intracellular Cd uptake. Intracellular Cd uptake, optimal at about pH 5.6, was highly sensitive to pH, which primarily affected the Vmax. Potassium, supplied at less than 1 mM, had no significant effect on Cd uptake. However, at concentrations greater than 1 mM, KNO3 caused both a stimulation in transport site activity and reduced affinity for Cd.Pretreatment with KNO3 removed potentially competing ions from the cell wall, altering the subsequent chemical equilibria established when moss shoots were incubated in Cd solutions. Reduced competition from ions removed by KNO3 pretreatment resulted in a higher affinity of both transport sites and extracellular exchange sites for Cd, Ca and Mg. The results demonstrate quantitatively the regulatory effects on intracellular metal uptake of the extracellular ionic environment provided by the cell wall.
The role of free radicals and radical processing systems in loss of desiccation tolerance in germinating maize (Zea mays L.)
Authors: LEPRINCE OLIVIER , DELTOUR ROGER , THORPE P. CHRIS , ATHERTON NEIL M. , HENDRY GEORGE A. F. 
Published: April 2006

SUMMARYOn germination, maize seeds rapidly become intolerant of desiccation. Germinating seeds exposed to dehydrating conditions for 24 h show a significant rise in lipid peroxidation and the accumulation of an electron paramagnetic resonance‐detectable organic radical, in parallel with the development of desiccation intolerance. Throughout the 5‐d‐long germination phase and the period of loss of desiccation tolerance, the radical scavengers α‐ and γ‐tocopherol and glutathione accumulate in response to episodes of dehydration. However dehydration suppresses, or delays, increases in activity of superoxide dismutase, peroxidase and glutathione reductase, major components in the protection against activated forms of oxygen. We present evidence of a sequence of events in which activated oxygen plays an early and probably causative role in loss of tolerance of desiccation in these seeds.
Some effects of nitrogen, phosphorus, potassium and carbon dioxide concentration on the morphology and vegetative reproduction of Sphagnum cuspidatum Ehrh.
Authors: BAKER R. G. E. , BOATMAN D. J. 
Published: April 2006

SUMMARYFive experiments are described which were designed to investigate the effects of varying the concentrations of nitrate, phosphate, potassium and carbon dioxide in the culture solution on the morphology and vegetative reproduction of Sphagnum cuspidatum Ehrh. The plants were grown axenically from spores sown on agar containing inorganic salts and then transferred to aqueous culture solutions through which air containing enhanced concentrations of carbon dioxide was passed.In three of the experiments the plants were grown in a balanced inorganic salt solution at various dilutions and in two of these the concentration of carbon dioxide in the gas bubbled through the solution was varied. The concentrations of nitrogen, phosphorus and potassium were varied independently and in combination in the remaining experiments while the concentration of carbon dioxide was kept constant.In some of the experiments the minimum concentrations of nitrogen and potassium supplied were considerably below the minimum average concentrations recorded in rain but the minimum concentration of phosphorus supplied was within the upper part of the range recorded in rain. Within the ranges supplied the concentrations of all three elements and of carbon dioxide affected interfascicle length and vegetative reproduction (innovation formation) but it was concluded that the element limiting innovation formation in natural conditions is phosphorus.
Kinetics of phosphorus uptake by the germ‐tubes of the vesicular–arbuscular mycorrhizal fungus, Gigaspora margarita
Authors: THOMSON B. D. , CLARKSON D. T. , BRAIN P. 
Published: April 2006

SUMMARYWe characterized kinetically the phosphorus (P) transport systems present in the germ‐tubes of the vesicular‐arbuscular (VA) mycorrhizal fungus, Gigaspora margarita Becker & Hall. Germinated spores of G. margarita were grown without P or with 1000 μM P for 10 d. The rate of P uptake by these spores and their associated germ‐tubes was measured at external P concentrations ranging from 1 to 10000 μM and in the presence or absence of an uncoupler of oxidative phosphorylation.Two transport systems for P were identified in the germ‐tubes of G. margarita grown without P. System I, an active high affinity system with a Km of 1.8–3.1 μM and a Vmax of 3.1–3.6 nmol mg protein−1h−1and System II, a passive low affinity system with a Km of 10200–11 300 μM and a Vmax of 445–895 nmol mg protein−1h−1. These two systems operated simultaneously at concentrations of P ranging from 1 to 10000 μM. Two transport systems for P were also identified in the germ‐tubes of G. margarita grown with 1000 μM P. The Km of System I in these germ‐tubes (13.4 μM) was increased relative to the Km of System I in germ‐tubes grown without P. There was also evidence to suggest that the Km of System II was increased in germ‐tubes grown with 1000 μM P.The values of Km and Vmax for the P transport systems in the germ‐tubes of G. margarita are similar to those observed in the hyphae of other fungi and in plant roots.
Aluminium polyphosphate in the ectomycorrhizal fungus Suillus variegatus (Fr.) O. Kunze as revealed by energy dispersive spectrometry
Authors: VÄRE H. 
Published: April 2006

SUMMARYThe aluminium detoxification mechanism of an ectomycorrhizal fungus, Suillus variegatus (Fr.) O. Kunze, grown on Petri dishes was studied using an atomic absorption spectrometer (AAS) and scanning transmission electronmicroscope with an electron dispersion photometer (STEM‐EDS). Higher concentrations of soluble Al in the growth medium resulted in abundant formation of aluminium polyphosphate granules in the hyphae, which have not been noted earlier in ectomycorrhizal fungi or in their mycorrhizas. EDTA washing and STEM‐EDS demonstrated that the granules were mainly located in the cell walls. The results suggest that growth of the fungal mycelium decreased as a result of higher Al and lower P concentrations inside the cells, as measured by AAS. The aluminium polyphosphate granules also contained varying amounts of other elements such as Ca, Cl, K, S, and Si.