bluuebunny/crossref_metadata_2025_split huggingface dataset:
Atmospheric pollution and the sensitivity of stomata on barley leaves to abscisic acid and carbon dioxide
Authors: ATKINSON C. J. , WOOKEY P. A. , MANSFIELD T. A. 
Published: April 2006

summarySpring barley (Hordeum vulgare L. cv. Klaxon) plants were exposed to mixtures of SO2+ NO2 (at concentrations of 24–35 nl l−1of each gas, depending upon fumigation system), or to charcoal‐filtered, or unfiltered ambient air during the period in which the second, and subsequent, leaves were emerging. The ability of individual detached leaves to regulate water loss was then examined after terminating the pollutant treatment.Observations of diurnal changes in stomatal resistance of well‐watered plants, using a viscous flow porometer, failed to indicate any major alterations which could be attributed to prior exposure to SO2+ NO2. By contrast, when an ABA solution (10−1mol m−3) was applied to detached leaves, the stomata of polluted plants were less responsive than plants previously exposed to control air. The dynamics of the observed responses strongly implicated impaired physiology of the guard cells rather than mechanical changes in the epidermis that might, for example, result from damage to the cuticle. Stomatal closure was considerably slower in polluted leaves compared with the controls. This decline in responsiveness to ABA was observed using leaves excised from well‐watered plants and in the absence of any externally visible injury.The ability of stomata to respond to a range of CO2 concentrations from 195–735 μmol mol−1was also examined using individual leaves, attached to the plant, in an environmentally controlled cuvette. Here the stomata of leaves which had been fumigated with SO2+ NO2 behaved in a similar manner to the non‐fumigated leaves, both showing closure in elevated CO2 concentrations.
A comparison of foliar wettability of red spruce and balsam fir* growing at high elevation
Authors: BOYCE RICHARD L. , McCUNE DELBERT C. , BERLYN GRAEME P. 
Published: April 2006

summaryThe contact angle method was used to determine the wettability of red spruce (Picea rubens Sarg.) and balsam fir [Abies balsamea (L.) Mill.] foliage in subalpine sites (1010–1400 m above sea level) at three locations in northern New England, USA (Camels Hump in Vermont and Mt. Moosilauke and Mt. Washington in New Hampshire).The dependence of contact angle (θ) on foliage age (t, in months) could be expressed in the form θ=θ1+θ2 e−kt. The value of the decay constant (k) ranged from 0.02 to 0.12 (month−1), depending upon location, but was independent of elevation, canopy position, and, in most cases, species. The asymptotic value of the contact angle (θ1) i.e. that approached by very old foliage, did not differ between species at some sites but was greater in fir than in spruce at others. The value of θ1 decreased with elevation in both species and tended to increase with an increase in height within the canopy. The value of the component which affected contact angle variation with age (θ2) was always greater in fir than in spruce, but was unaffected by elevation; in fir, it appeared to increase with height in the canopy. Thus, the estimated value of the initial (t= 0) contact angle (θ1+θ2) was greater in fir, increased with height in the canopy, and decreased with elevation. The overall pattern found was that (1) young foliage of spruce is more wettable than young foliage of fir, but the difference becomes smaller in older age classes; (2) young foliage near the bottom of the canopy is more wettable than near the top; and (3) foliage from a given age class and species is more wettable at higher elevations.The treatment of foliage with xylene to remove epicuticular wax decreased contact angles of fir but increased them in spruce. Scanning electron microscopy revealed that wax removal by xylene did not mimic natural wax removal. Contact angles obtained with acidified water did not vary significantly from those obtained with deionized water.
Absorption of atmospheric NO2 by spruce (Picea abies L. Karst.) trees
Authors: THOENE BARBARA , SCHRÖDER PETER , PAPEN HANS , EGGER ALFRED , RENNENBERG HEINZ 
Published: April 2006

summaryWhen spruce (Picea abies L., Karst.) branches were exposed to 5.2–18.7 nl NO2 l−1the flux to the shoots increased linearly with increasing NO2 concentrations. At NO2 concentrations below 2.6 nl l−1uptake of NO2 by the shoots was not observed. The measured flux of NO2 to the shoots was found to be lower than the NO2 flux predicted from the shoot conductance to diffusion of H2O. These results are consistent with the existence of internal resistances for NO2 influx, e.g. production and emission of NO2 by the leaves. However, emission of NO2 was not observed. When the NO2 flux to the shoots was plotted versus transpiration rate, a linear increase was found with an y‐axis intercept. The intercept may be interpreted as the NO2 flux to the cuticle and the bark; its value increased with increasing atmospheric NO2 concentrations.The flux of NO2 to the shoots showed diurnal variation with high levels in the light and low levels during darkness. NO2 flux to the branches was dependent on light intensity. This dependency can largely be explained by light dependent changes in shoot conductance. Daytime light intensity determined also the night‐time shoot conductance and, hence, the NO2 flux to the branches during the night. The ratio of NO2 flux to transpiration rate was higher in the dark than in the light. Whether this observation can be explained by a light dependency of internal resistances remains to be elucidated.The absorption of NO2 by the shoots enhanced the in vitro NR activity of the needles, while NiR and GS activities were not increased significantly. One day after exposure to NO2 concentrations of 60 nl l−1, nitrate reductase (NR) activity was three times higher than that of untreated controls. However, after three days of NO2 exposure the NR activity declined to the level of untreated controls. Apparently, the increased in vitro NR activity upon NO2 fumigation is a transient phenomenon in spruce needles. The regulatory events that may modulate NR activity of the needles, when exposed to atmospheric NO2, are discussed.
The role of nitrogen concentration in determining the outcome of the interaction between Dactylorhiza incarnata (L.) Soó and Rhizoctonia sp.
Authors: BEYRLE H. , PENNINGSFELD F. , HOCKF B. 
Published: April 2006

summaryProtocorms of Dactylorhiza incarnata (L.) Soó grown in shaking cultures were used for synthesis of mycorrhizas on agar plates in the presence of a Rhizoctonia strain. At low nitrogen (N) concentration [0.36 m++++m Ca (NO3)2.4H2O] normal mycorrhizas were formed, whereas the same concentration of carbon a higher concentration of N (3.6 mm) led to parasitism with low survival of protocorms. Carbon source did not influence the symbiotic interactions. Growth of mycorrhizal protocorms at low N concentrations increased with sucrose concentrations up to 58 mm, but in the absence of the fungus there was practically no growth.Increases in nitrogen concentration can thus lead to change from a mycorrhizal to a parasitic interaction. The effects of nitrogen on the interaction between fungus and orchid provided an experimental system which was subsequently used to investigate hormone production in the different types of symbiosis by enzyme immunoassays. Phytohormone levels remained low under asymbiotic conditions. The presence of the fungus led to a large increase in phytohormone concentration, which was correlated with a growth stimulation in mycorrhizal protocorms. In parasitized protocorms auxin and to a lesser extent cytokinins remained at higher concentrations for longer than in mycorrhizal protocorms. It is thought that the phytohormones are derived mainly from the mycorrhizal fungus.
In vitro synthesis of ectomycorrhizas on Casuarinaceae with a range of mycorrhizal fungi
Authors: THEODOROU COSTAS , REDDELL PAUL 
Published: April 2006

summaryEleven species of mycorrhizal fungi, selected from stands of either Eucalyptus spp., Allocasuarina spp. or Pinus radiata D. Don were tested in an aseptic system for their abilities to initiate ectomycorrhiza with Allocasuarina littoralis (Salisb.) L. Johnson, Casuarina equisetifolia ssp. equiselifolia L. and C. cunninghamiana Miq. Elaphamyces sp., Hysterangium sp., Laccaria laccata (Scop ex Fr.) Bk. & Br., Pisolithus tinctorius (Pers.) Coker & Couch, Scleroderma sp. and Thelephora terrestris (Ehrh.) Fr. formed ectomycorrhizas on all three hosts. Amanita sp. formed ectomycorrhizas on A. littoralis and C. cunninghamiana but not on C. equisetifolia. Paxillus involutus (Batch ex Fr.) Fr. formed ectomycorrhizas on A. littoralis only. P. tinctorius also formed ectomycorrhizas with C. obesa Miq. Rhizapogon luteolus Fr. & Nord, Suillus granulatus (L. ex Fr.) Kuntze and S. piperatus (Bull ex Fr.) O. Kuntze colonized the rhizosphere of Casuarinaceae but did not form ectomycorrhizas.The comparative intensity of ectomycorrhizal infection by P. tinctorius and L. laccata was assessed on four host species. Infection intensity ranged from 13 to 70%, of laterals infected and decreased for both fungal species in the order: A. littoralis > Eucalyptus pilularis Smith > C. equisetifolia > C. cunninghamiana.An exogenous supply of glucose induced greater and sometimes earlier, ectomycorrhizal infection of A. littoralis, C. equisetifolia and C. cunninghamiana by P. tinctorius and L. laccata than that in the absence of glucose. The optimum glucose level for these fungi and hosts in this synthesis system was 750 μg glucose (g soil)−1.
Root factors stimulate 32P uptake and plasmalemma ATPase activity in vesicular‐arbuscular mycorrhizal fungus, Gigaspora margarita
Authors: LEI J. , BÉARD G. , CATFORD J. G. , PICHÉ Y. 
Published: April 2006

summaryRoot‐inducing (Ri) T‐DNA transformed roots of carrot were used as the plant partner in a study of 32P absorption and plasmalemma ATPase activity in the hyphae of the vesicular‐arbuscular mycorrhizal fungus Gigaspora margarita Becker & Hall. Hyphae from germinating spores were grown in the presence or absence of root exudates and volatiles. In the presence of these root factors, 32P isotope labelling occurred in hyphae, auxiliary cells and spores, while in the absence of these factors, the labelling only occurred in fungal spores. Similarly, ATPase activity appeared on the fungal plasmalemma only in the presence of root factors. The use of the ATPase inhibitor, diethylstilbestrol, demonstrated the importance of plasmalemma ATPase in the stimulation of hyphal growth of this obligately biotrophic fungus.
Application of the diffusion equation for modelling splash dispersal of point‐source pathogens
Authors: YANG XIUSHENG , MADDEN LAURENCE V. , BRAZEE ROSS D. 
Published: April 2006

summaryA model of splash dispersal of point‐source pathogens is developed and parameterized from experimental data of Colletotrichum acutatum, the cause of strawberry anthracnose. Starting with analysis on a probability density function of a sum of random displacement vectors, the model turned out to be the fundamental solution of the classic diffusion equation. Model parameters were determined for three ground covers (plastic, soil, and straw) and two rain intensities (15 and 30 mm h−1). The nonlinear coefficient of determination varied from 0.80 to 0.96, indicating that the application of the diffusion equation is promising in modelling of splash dispersal processes from a point source over a homogeneous ground cover.
The action spectrum of far‐red light in interaction with orange light on orientation of chloroplasts in Mougeotia
Authors: LECHOWSKI Z. , BIAŁCZYK J. 
Published: April 2006

summaryChloroplast rotation from profile to face position in Mougeotia can be controlled by an interaction of far‐red and orange light during dichromatic irradiation. In experiments to determine the action spectrum in the far‐red light range during dichromatic irradiation, light conditions prevented the formation of a gradient of the far‐red‐absorbing form of phytochrome in the cell. Linearly polarized monochromatic light of 620 nm vibrating parallel to the cell axis or unpolarized far‐red light (700 run to 900 nm) when given alone had no effect on chloroplast reorientation to the face position. Unpolarized far‐red light in the range from 700 nm to 775 nm was active in an interaction with 620 nm monochromatic light and had its maximum effect on face chloroplast orientation at 710 nm. Wavelengths above 775 nm were ineffective. In this kind of chloroplast photoorientation in Mougeotia, high irradiance of both kinds of light together with prolonged exposure were necessary to obtain the full response. The time‐course response showed three phases: lag, movement and steady‐state. At the saturating dose of both kinds of light there was a 10–15 min lag period between the first detectable change in chloroplast position. Then the response was linear (movement phase) until after approximately 30 min when all the chloroplasts had become reorientated. Simultaneous irradiation of Mougeotia cells with green and far‐red light did not change the maximum activity in far‐red light. The effect was similar when treatment with one kind of light e.g. orange or far‐red light, was followed by the other. The photo responses of Mougeotia chloroplasts are typical of the high irradiance reactions that control many photomorphogenetic processes.
Concurrent exposure to SO2 and/or NO2 alters growth and yield responses of wheat and barley to low concentrations of O3
Authors: ADAROS G. , WEIGEL H. J. , JÄGER H. J. 
Published: April 2006

summaryDuring 1988 and 1989, single and interactive effects of low concentrations of O3, SOS and NO2 (6–44, 9–63 and 10–43 μm−a as 24 h daily means) on two varieties of spring barley (Hordeum vulgare L., ‘Arena’ and ‘Alexis’) and spring wheat (Triticum aestivum L., ‘Turbo’ and ‘Star’) were investigated in factorial experiments using open‐top chambers. Potted plants were exposed during the whole growing season to either charcoal‐filtered air (CF; control) or CF supplemented with one (SO2, NO2) or two (O3) concentrations of the pollutants. While SO2 was applied continuously, fumigation with O3 and NO2 occurred every day sequentially from 8.00 to 16.00 and from 16.00 to 8.00 h, respectively. Analysis of variance indicated that from the main treatments O3 caused the most detrimental effects on growth and yield parameters. Depending on season and on variety, yield of wheat was reduced by O3 between 20% and 40% compared with the control treatment; a significant reduction of yield of barley (−15%) was only registered for ‘Arena’ (1988), while ‘Alexis’ appeared to be insensitive towards this gas. SO2 did not affect yield of barley significantly, while yield of wheat was either decreased (−7% for ‘Turbo’ in 1988) or increased (+11% for ‘Star’). NO2 did not alter yield of wheat significantly but it increased yield of barley (‘Arena’) by 15% in 1988. Significant interactive effects between the pollutants were observed only for a few parameters. Among these the most sensitive ones were the length of ears, the 1000‐grain weight and the weight of straw. The interaction between the pollutants was mostly antagonistic, i.e. positive or negative effects of a single gas were cancelled or mitigated by the presence of other pollutants. However, a clear tendency towards a synergism was found for wheat in 1988: detrimental effects of O3 on yield (e.g, –26%;‘Turbo’) were aggravated by the addition of either SO2 (−38%) or, partially, NO3 (−31%) or both pollutants together (−44%). Before the plants were fully mature, visible symptoms were only observed on wheat after exposure to the highest O3 concentrations. The results showed that although effects of O3 dominated, these responses were strongly modified by the presence of one or both of the other gases. It is evident that yield losses of O3‐sensitive crop species may be enhanced under certain circumstances by low concentrations of other pollutants. Therefore, estimations of yield losses from open‐top chamber experiments should consider interactive effects between those pollutants which are relevant to ambient air.
Unusual patterns in the distribution of calcium oxalate in spruce needles and their possible relationships to the impact of pollutants
Authors: FINK SIEGFRIED 
Published: April 2006

summaryThe patterns of distribution of calcium oxalate crystals in spruce needles have been investigated in healthy needles and those subjected to either acid precipitation (ph 2.5) or various ozone fumigations. In the acid treatment, deposits of Ca oxalate were lacking in the outer walls of the epidermal cells. Under the impact of ozone, unusual complexes of Ca oxalate crystals embedded in a matrix of callose and cellulose projected from the walls inwards into the cells, filling the lumina of epidermal and hypodermal cells completely. In mesophyll cells, the complexes projected more or less from the walls into the vacuoles. In other cases, crystals appeared within the vacuoles of mesophyll cells. In dead cells, precipitates of Ca oxalate or phosphate apparently indicate destruction of the cytoplasm after a major influx of Ca2+. It is speculated, that the physiological significance of enhanced calcium leaching has been overestimated. With regard to ozone impact, it seems that the major problem of thereby enhanced membrane permeabilities may not be an increased efflux of mineral elements, but rather an increased influx of Ca into the symplast and subsequent disturbances in metabolism.
Uptake of NOxby mycorrhizal and non‐mycorrhizal Scots pine seedlings: quantities and effects on amino acid and protein concentrations
Authors: NÄSHOLM TORGNY , HÖGBERG Peter , EDFAST ANN‐BRITT 
Published: April 2006

summaryScots pine seedlings were grown from sterilized seeds in oven sterilized sand. Half of the seedlings were inoculated with the mycorrhizal fungusPisolithus arhizus(Pers.) Rausch (syn.Pisolithus tinctorius)while the rest were not. Seedlings were raised in a growth chamber for 61 d and supplied with a complete nutrient solution with NH4Cl as the nitrogen source. To measure uptake of NO2by the15N dilution method, nitrogen in the nutrient solution was enriched with 5.00 atom %15N. After 61 d pretreatment, all seedlings were transferred to cuvettes, and exposed to either 20–30 ppb NOxor carbon‐filtered air for 39 d. Seedlings harvested just prior to, and after 19 and 39 d exposure were analysed for growth and concentrations of total nitrogen and atom %15N in roots and shoots and free amino acids and total protein in shoots. As a measure of mycorrhizal infection the concentration of ergosterol in roots was determined.Exposure of seedlings; to low concentrations of NOxhad no effect on growth, total nitrogen concentration, ergosterol concentration or total protein concentration. The atom %15N of seedlings increased and asymptotically approached that of the nutrient solution. Because differences in uptake of nitrogen from soil resulted in various values on atom %15N irrespective of exposure, quantification of uptake of NOxwas not possible with the formula previously used for this purpose. By calculating the atom %15N of the nitrogen taken up by plants between two harvests, and comparing this value for exposed and non‐exposed seedlings, uptake of nitrogen from NOxcould be quantified. The uptake of nitrogen from 20–30 ppb NOxthus calculated amounted IO, on average 1.4% of the total uptake of nitrogen by seedlings during exposure. After 19 d exposure nitrogen derived from NOxwas found in both shoots and roots indicating transport of nitrogen from shoots to roots. After 39 d exposure, negative values of uptake of NOxwere found in roots. This might be explained as an effect of decreased transport of NO, derived nitrogen from shoots and roots and/or decreased transport of soil derived nitrogen from roots to shoots. Glutamine, arginine and GABA+ proline were the most abundant amino acids detected in the seedlings. Exposure to NOx. resulted in lower concentrations of GABA+ proline but had no significant effect on concentrations of glutamine and arginine. Higher concentrations of glycine were found in exposed seedlings but this represented only a small fraction of the total amount of amino acids in the shoots. Inoculated seedlings were smaller and had significantly higher concentrations of glutamine and arginine compared with those that were not inoculated.Thus, 40 d exposure to 20–30 ppb NO, had no effect on seedling growth, mycorrhizal infection or total nitrogen concentration, but resulted in a significant uptake of NOxand measurable changes in amino‐acid composition.
Fluxes of carbon and phosphorus between symbionts in willow ectomycorrhizas and their changes with time
Authors: JONES MELANIE D. , DURALL D. M. , TINKER P. B. 
Published: April 2006

summaryOne way of viewing a mycorrhizal symbiosis is as a balance between the nutritional ‘benefits’ and carbon ‘costs’ to the phytobiont. Phosphorus acquisition efficiency (the amount of phosphorus taken up per unit of carbon allocated belowground) can be used as an indicator of this balance. In this study, phosphorus uptake and belowground carbon allocation were measured using ectomycorrhizal (M) (Thelephora terrestris (Ehrh.) Fr.) and non‐mycorrhizal (NM) Salix viminalis L. cv. Bowles Hybrid. Following 50, 60, 85 or 98 d of growth in a gamma‐irradiated soil/sand mixture containing 4 mg bicarbunate‐extractable P kg−1, seven randomly‐selected cuttings of each treatment were harvested and their P contents determined. Nine d prior to each harvest, the three median plants from the group of seven were pulse labelled with 14C to determine the relative allocation of C aboveground and belowground. Mycorrhizal colonization of willow caused a two‐fold increase in growth owing to substantially higher P uptake. Phosphorus inflow rates were almost three times as high for M root systems as for NM root systems over the interval up to the first harvest (3.2 × 10 −12 and 1.2 × 1012 mol m−1 s–1, respectively). Over the interval from 50 to 98 d, inflows into M plants were 50% higher than into NM plants (1.4 × 1012 and 0.9 × 10−13 mol m−1 s−1 respectively). The M plants allocated about 25 times as much carbon belowground as the NM plants for both periods. The P acquisition efficiency was higher in M than in NM plants during the first interval (16% and 40% higher using two different calculation methods), whereas during the second interval it was higher in NM than in M plants (33% and 44% higher using the two different methods). Thus, ectomycorrhizas can be very effective in supplying P to their hosts even at an early stage of infection. Furthermore, it is suggested that a temporal separation exists in the maximal fluxes of P and C between the fungus and the host of the mycorrhizal association. The results are discussed in the context of the nutrient requirements and carbon economies of field‐grown woody plants.
Fructan composition in adventitious tuberous roots of Viguiera discolor Baker (Asteraceae) as influenced by daylength
Authors: ISEJIMA E. M. , FIGUEIREDO‐RRIEIRO R. C. L. , ZAIDAN L. B. P. 
Published: April 2006

summaryShort (8–10h) photoperiods stimulated branching, flowering and enlargement of adventitious tuberous roots of Viguiera discolor Baker, a native plant of the Brazilian cerrado. Inulin was mostly accumulated in parenchyma cells associated with secondary xylem of tuberous roots. Accumulation was greater in plants grown under conditions that induce flowering (1) than in plants grown under conditions that do not induce flowering (NI) (photoperiods longer than 12 h), Although total fructan concentration was similar in both conditions [approx. 460 mg (g dry mass)−1], the amount of inulin in I was 10 times that of oligosaccharides, whereas in NI it was 6 times greater. In addition, the relative molecular mass of inulin was slightly lower in NI 16600) than in I (18600), but considerably higher than those reported for other Asteraceae (approx. 5500). The results suggest that flower‐inductive conditions affect fructan metabolism in Viguiera discolor without altering the total fructose.