bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of NH3 and SO2 on the growth and competitive ability of Arnica montana L. and Viola canina L
Authors: DUECK TH. A. , ELDERSON J. 
Published: April 2006

summaryThe effects of atmospheric NH3 and SO2 separately and in combination on the growth and competitive ability of three species of the Violion caninae alliance were investigated. Growth and nutrient concentrations of Viola canina and Arnica montana in mixed culture with Agrostis capillaris were examined in relation to that in monoculture. Seedlings were transplanted into heathland topsoil in pots and placed in open‐top chambers for 9 months from autumn to summer, where they were exposed to ambient air, 90 μ m−3 SO2, 50 μg m−3 NH3 and to the combination of NH2 and SO2. In the NH3+ SO2 treatment, a more‐than‐additive increase in nitrogen and sulphur concentrations was observed indicating co‐deposition. NH3 influenced the nutritional status of V. canina the most, increasing the nitrogen, phosphorus, and magnesium concentrations and reducing those of potassium and calcium. NH3 fumigation significantly stimulated shoot growth of all three species and root growth of A. capillaris, while SO2 reduced only the root growth of A. capillaris. The relative yield of V. canina was reduced by 20–30% in the presence of the air pollutants. The relative yield of A. montana was stimulated by 30–40% in treatments including SO2 compared with that in ambient air or NH3 alone. The competitive ability of both dicotyledons in mixed culture with A. capillaris was strongly reduced by NH3 and was unaffected by SO2. The consequences of exposure to NH3 and SO2 for the survival and maintenance of threatened species in heathland vegetation are discussed.
Stolon growth and branching in Glechoma hederacea L.: an application of a plastochron index
Authors: BIRCH C. P. D. , HUTCHINGS M. J. 
Published: April 2006

summaryStolon growth and branching in Glechoma hederacea L. was analyzed, using a plastochron index based on the number of ramets on each stolon and internode growth. New methods, employing this index, were used to detect fluctuations in the rate of stolon extension, and to analyse the development of secondary stolons. The plastochron index had a strong linear correlation with time, with a new primary ramet appearing every 3.5 d. The overall stolon extension rate fluctuated between 1.9 and 2.9 cm d−1 through each plastochron cycle. The age at which each node produced secondary stolons was related to its position on the plant, but the initial rates of secondary stolon development differed little between nodes. Rate of development of secondary stolons was strongly correlated with the time at which they started to grow. Thus, later developing secondary stolons grew more slowly than those developing earlier from nodes in equivalent positions.
Nuclear magnetic resonance (NMR) micro‐imaging of ripening red raspberry fruits
Authors: WILLIAMSON B. , GOODMAN B. A. , CHUDEK J. A. 
Published: April 2006

summaryRed raspberry (Rubus idaeus) fruits were subjected to nuclear magnetic resonance (NMR) micro‐imaging to study the changes in spatial distribution of mobile protons (1H) during a 3‐day ripening period while the fruit was still attached to the receptacle. All imaging measurements were made using the protons from a single absorption peak at 4.6 ppm, which corresponds to water, and data were collected by pulsed gradient spin‐echo and gradient‐echo methods with voxel dimensions of 70 × 70 × 500 μm. Individual drupelets were clearly visible by this non‐invasive histological method in distal transverse ‘slices’ of a newly harvested red ripe fruit viewed by spin‐echo; highest mobile proton densities were found at the lines of contact between drupelets. The mesocarp tissues of each drupelet showed intermediate grey tones with some evidence of radial striations. In more proximal ‘slices’ the surface of the receptacle and its central vascular cylinder had the highest mobile proton densities. The seeds produced black images in all ‘slices’, indicative of low mobile proton densities or long relaxation times.After 3 days the proximal ring of drupelets separated from the receptacle, the spaces between drupelets enlarged slightly and the boundaries between drupelets were less pronounced. Vascular bundles in the receptacle lost their whitish radiating pattern in proximal ‘slices’ almost completely, indicating that mobile protons were less abundant after abscission of drupelets.The same ‘slices’ viewed by gradient echo were less discriminating for localization of Seeds and pronounced tangential wave patterns, often overlaying radial striations, presented more complex images than those seen by spin echo.
Effects of simulated nitrogen rich and acid rain on the nitrogen‐fixing lichen Peltigera aphthosa (L.) Willd.
Authors: HALLINGBÄCK TOMAS , KELLNER OLLE 
Published: April 2006

summaryThe nitrogen‐fixing lichen Pettigera aphthosa (L.) Willd. was treated under semi‐natural conditions with simulated rain containing different combinations of ammonium, nitrate and sulphuric acid. Nitrogen in neutral solution had no negative effect on the nitrogen fixation rate. Sulphuric acid had a negative effect on nitrogen fixation rate, especially in combination with ammonium. The results could suggest an explanation for the sudden decline of P. aphthosa in southern Sweden.
Utilization of organic and inorganic nitrogen sources by ectomycorrhizal fungi in pure culture and in symbiosis with Pinus contorta Dougl. ex Loud.
Authors: FINLAY R. D. , FROSTEGÅRD Å. , SONNERFELDT A.‐M. 
Published: April 2006

summaryThe growth of ten species of ectomycorrhizal fungi was measured in liquid media containing different organic and inorganic nitrogen sources. All fungi grew well on ammonium. Growth on nitrate was generally lower, although there was considerable variation between different isolates of the same species. Suillus variegatus, Piloderma croceum, Paxillus involutus, Hebeloma crustuliniforme and unidentified pink and white isolates often grew as well on organic nitrogen sources as on ammonium. Growth of the other species was more variable. Isolates of Thelephora terrestris and Lactarius rufus varied in their ability to use bovine serum albumen (BSA) but two Laccaria species were poor at using the protein as a nitrogen source. The ability of mycorrhizal and non‐mycorrhizal Pinus contorta Dougl. ex Loud, plants to utilize BSA was also examined. Non‐mycorrhizal plants and mycorrhizal plants infected with either T. terrestris or the unidentified pink ectomycorrhizal symbiont were supplied either with ammonium or with BSA. Growth of plants supplied with BSA was significantly increased by mycorrhizal infection with the pink symbiont and not significantly different from that of plants supplied with ammonium, but non‐mycorrhizal plants were unable to use the protein as a nitrogen source and had significantly lower yields and nitrogen contents than infected plants. In contrast, mycorrhizal infection with T. terrestris had no effect on growth or nitrogen contents of plants supplied with protein. The results are discussed in relation to possible physiological differences between ectomycorrhizal fungi occurring at different successional stages of forest development.
Electron transport in thylakoids isolated from barley leaves infected by the powdery mildew fungus (Erysiphe graminis DC. ex Merat f.sp. hordei Marchal)
Authors: HOLLOWAY PETER J. , MACLEAN D. J. , SCOTT K. J. 
Published: April 2006

summaryBarley leaves infected with powdery mildew fungus (Erysiphe graminis DC. ex Merat f.sp. hordei Marchal) show an accelerated loss of chloroplast photochemical activities and electron transport components, compared to the losses which occur during senescence of non‐infected controls. Concentrations of electron earners and rates of light‐saturated photochemical activities were measured at selected times after inoculation, in an endeavour to identify rate‐limiting components of the electron transport chain in infected leaves. It has previously been demonstrated that the rate‐limiting step in non‐infected leaves is the transfer of electrons from PQ to the cyt f/b6 complex.When compared on a fresh weight basis, the concentration of all electron carriers (P700, cyt f, cyt b559 H.P., and the photoreducible pool of PQ), and all photochemical activities (H2O → PS2 → PS1, H2O → PS2, DONOR → PS1), decreased more rapidly in infected leaves, when compared with non‐inoculated controls of the same age, starting from 4 d after inoculation. When expressed on a chlorophyll basis, concentrations of the electron carriers and rates of the photochemical activities were identical for infected and control leaves of the same age.These data suggest that the rate‐limiting step of non‐cyclic electron transport is the same in both infected and control leaves (PQ→cyt b6/f complex). It is proposed that in infected leaves, superimposed on normal chloroplast senescence, there is an accelerated loss of electron carriers and associated photochemical activities resulting from the breakdown of whole regions of thylakoid membranes.
Effect of sodium chloride on growth and nitrogenase activity in seedlings of Myrica cerifera L.
Authors: SANDE EVE , YOUNG DONALD R. 
Published: April 2006

summaryThe actinorhizal shrub, Myrica cerifera L., is widespread in coastal areas where it may be exposed to variable saline conditions. In growth chamber studies, 5‐month‐old seedlings remained viable during exposure to 150 mM NaCl for 35 d, though concentrations above 50 mM significantly depressed plant and root nodule growth. Concentrations of NaCl above 50 mM also depressed stomatal conductance to water vapour diffusion and net photosynthetic rates. Relative to control plants, nitrogenase activity per g dry weight of nodules decreased for 21 d in plants subjected to a range of NaCl concentrations. By day 35. plants exposed to 25 and 50 mM NaCl had recovered some nitrogenase activity relative to the controls, whereas plants receiving 100 and 150 mM had not. At 35 d, plants treated with 150 mM NaCl had a rate of N2 fixation per g dry weight of nodule tissue 26% of that in control plants. However, no mortality had occurred, and full recovery followed the conclusion of the experiment. Thus, although periodic natural increases in salinity from sea spray or storm overwash may not lead to plant mortality, growth and N2 fixation will be significantly decreased in M. cerifera.
External hyphae of vesicular‐arbuscular mycorrhizal fungi associated with Trifolium subterraneum L.
Authors: JAKOBSEN I. , ABBOTT L. K. , ROBSON A. D. 
Published: April 2006

summaryVariation among VA mycorrhizal fungi in their ability to enhance phosphorus uptake and plant growth could be due to differences in the length, distribution and phosphorus uptake of external hyphae. Trifolium subterraneum L. was grown in a sandy soil in association with the VA mycorrhizal fungi Acaulospora laevis Gerdemann & Trappe, Glomus sp., Scutellospora calospora (Nicol. & Gerd.) Walker & Sanders or left uninoculated. When mycorrhizas had become well established, plants were transferred to a two‐compartment system, where root growth into a hyphal compartment was restricted by a fine nylon mesh. Spread of hyphae into the hyphal compartment was monitored by sequential sampling of soil cores at different distances from the root compartment. Plants were harvested at three times.The spread of hyphae differed between fungi. The length density of hyphae of S. calospora declined approximately exponentially with increasing distance from the roots, whereas A. laevis maintained a plateau of constant hyphal density up to 7 and 11 cm from the roots after 28 and 47 d, respectively. Glomus sp. had an intermediate pattern of spread with a plateau closest to the roots followed by an exponential decline. The average rate of hyphal spread (mm d−1) was 3.1 for A. laevis but only 0.7–0.8 for Glomus sp. and S. calospora. In addition to its more extensive hyphal spread, A. laevis produced the largest increases in phosphorus uptake and plant growth. All mycorrhizal plants had a larger phosphorus inflow than the non‐mycorrhizal controls, but the phosphorus inflow per unit mycorrhizal root length was 25.3 times as high with A. laevis as with the two other fungi. These differences between the fungi became even more pronounced when the phosphorus inflow was expressed on the basis of hyphal length.This work indicates that the efficiency of phosphorus uptake by a VA mycorrhizal fungus is strongly affected by its spatial distribution of hyphae in the soil, and possibly also by differences in capacity for uptake by unit length of hypha.
Antagonistic effects of simultaneous exposure to sulphur dioxide gas and vapour of the herbicide 2, 4‐D iso‐octyl on the carbon dioxide exchange of tomato and field bean plants
Authors: BREEZE VICTOR G. , FOWLER ALISON T. 
Published: April 2006

summaryTomato and field bean plants were exposed simultaneously to SO2 gas (in the range 0.07–0.57 μg 1−1) and to vapour of the herbicide [14C]2, 4‐D iso‐octyl (0.8–2.7 ng 1−1), for periods of 6–24 h in an air‐flow system at a water vapour pressure deficit of >2 kPa. Greater response was shown by the plants to 2, 4‐D vapour than to SO2. Herbicide vapour alone decreased CO2 exchange during the 3 d experimental period in both species, but the combination of herbicide plus SO2 had less effect. The response by tomato was both greater and more rapid than by field bean (which showed an initial stimulation of CO2 exchange due to 2, 4‐D), and the two species differed in the effect on transpiration. SO2 did not affect the uptake and distribution of herbicide within the plants. It appeared that 2, 4‐D iso‐octyl vapour and SO2 were antagonistic in effect on the CO2 exchange of the two species under the experimental conditions, and that in tomato this was largely due to changes in stomatal conductance.
Foliar uptake and release of inorganic nitrogen compounds in Pinus sylvestris L. and Picea abies (L.) Karst.
Authors: WILSON E.J. 
Published: April 2006

summaryFoliar uptake and release of inorganic nitrogen compounds were studied by immersing current‐year shoots of Scots pine (Pinus sylvestris L.) and Norway spruce [Pica abies (L.) Karst] in either NH4+‐ or NO3−‐rain solutions at different N concentrations. The effects of N form, N concentration and tree species on ion influx and efflux were investigated.Spruce shoots absorbed NH4+ from the external solution. Uptake apparently occurred by diffusion rather than by H+ or base cation exchange as commonly accepted, and increased linearly with NH4+ concentration in the external solution. In contrast, pine shoots released NH4+to the external solution. The different reactions of spruce and pine may reflect species differences in physical and chemical properties or differences in tissue N concentration. If the latter is the case, a tree's N status may determine whether the canopy acts as a source or sink for NH4+ influencing deposition rates to the needle surface. The results show that where NH4+ concentration on the needle surface exceeds 4 mg 1−1, foliar uptake may make a significant contribution to N status. In the absence of NH4+‐base cation exchange, atmospheric inputs of NH4+to the canopy appear unlikely to be directly‐responsible for the nutrient deficiencies typical of Dutch forest decline.Neither spruce or pine shoots were able to utilize NO3− in the external solution and generally released NO3−. Adverse effects resulting from foliar accumulation of wet‐deposited NO3− appear unlikely. However, higher NO3− concentrations and longer residence times than simulated in this experiment may result in foliar uptake of NO3− in the field.
Ultrastructural studies on differentiating chloroplasts in the ‘forma fuscoviridis’ of Ceratozamia mexicana Brongn.*
Authors: BONZI LAURA MORASSI , BONATTI PIERA MEDEGHINI , MARINI CECILIA , FORNASIERO ROBERTA BARONI , PAOLETTI CINZIA 
Published: April 2006

summaryChloroplast ontogenesis has been examined ultrastructurally in leaflets of ‘forma fuscorviridis’ of Ceratozamia mexicana Brongn., a cycad displaying a dark red‐brown colour in young developing leaves. In very young leaves the chloroplasts contain large paracrystalline prolamellar bodies (PLBs), widely extending thylakoid strips, starch, membrane‐bounded paracrystals (MbPs) and conspicuous electron‐dense plastoglobules (PGBs) densely packed around the PLBs. All these features progressively disappear as the development of the thylakoid system proceeds. In mature leaves the chloroplasts are characterized by randomly orientated grana stacks containing large numbers of thylakoids. The conspicuous presence of different membrane precursors during leaf ontogeny may be associated with the very low rate of leaf development in Ceratozamia.
The ecological status of grey alder (Alnus incana (L.) Moench) in the upper subalpine birch forest of the central Scandes
Authors: KULLMAN LEIF 
Published: April 2006

summaryElevational distribution, site characteristics and regeneration patterns of grey alder [Alnus incana (L.) Moench] have been studied in subalpine forest of the southern Swedish Scandes, mainly as a basis for paleoecological inferences. Alder occurs very sparsely in the mountain birch forest and is strictly confined to sites with fresh finegrained soils with an insignificant mor humus layer. It frequently grows in close association with moving water (inundation in the spring). The potential climatic tree‐limit is inferred to appear about 30 m below that of mountain birch. Within a more than 200 m broad vertical zone below the tree‐limit, sexual reproduction does not take place at the present. Conceivably, the alders here are old relicts from a warmer period in the past. In contrast to other tree species, the range‐limit did not advance altitudinally in response to the 20th century warming (up to the 1930s/1940s) and a non‐equilibrium relationship with climate is hypothesized to have developed after the maximum range extension in the early‐ or mid‐Holocene. The virtual extinction of alder in the upper subalpine forest during the late Holocene is understandable in terms of pronounced thermophily of generative life‐cycle stages and a narrow range of soil preference. Both these properties are acting regressively on reproductive success as a consequence of climatic cooling and long‐term soil deterioration.
A containerized staining system for mycorrhizal roots
Authors: Claassen V. P. , Zasoski R. J. 
Published: April 2006

summaryA useful device for manipulating root segments during clearing and staining of VA mycorrhizal roots is described. The device is constructed by cutting the tip off of a disposable syringe and welding a polypropylene screen on to the barrel. With this system, the plunger is used to draw in or expel reagents rapidly with little or no loss of root material during the repeated changing of reagents. The system speeds the process of clearing and staining and reduces the potential for operator contact with reagents.
Amelioration of aluminium toxicity in wheat by fluoride
Authors: MacLEAN D. C. , HANSEN K. S. , SCHNEIDER R. E. 
Published: April 2006

summaryThe deleterious effects of aluminium in the rhizosphere on growth, root morphology, ion uptake, and stomatal conductance in wheat (Triticum aestivum L.) were prevented or attenuated by the inclusion of fluoride in the growth medium; the more fluoride present relative to the concentration of aluminium, the greater the alleviation. Results support the conclusion that the ameliorative effects of fluoride were due to reductions in the concentration of the rhizotoxic trivalent cation (Al3+) through the formation of aluminium–fluoride complexes that are neither phytotoxic nor readily translocated from roots to shoots.
The use of ion‐selective microelectrodes for measuring calcium and hydrogen ion transfer between foliar surfaces and simulated rain solutions
Authors: LAUVER T. L. , MCCUNE D. C. , SHAFF J. E. , KOCHIAN L. V. 
Published: April 2006

summaryA method is presented for the rapid and quantitative assessment of the transfer of calcium (Ca2+) and hydrogen (H+) ions between the surface of a leaf and simulated acidic rain. A small volume (144 μl) of pH 3.5 simulated rain solution was confined within a rigid, Teflon capillary on the foliar surface. A liquid membrane‐type, neutral carrier‐based, ion‐selective microelectrode either for Ca2+or for H* was placed within the capillary with the tip of the microelectrode at least 100μm from the foliar surface. This allowed spatial and temporal aspects of ion gradients generated by ion diffusion from the foliar surface to be studied. Results indicate that, throughout a 60–minute period after contact of simulated rain with the adaxial foliar surface of spinach (Spinacea oleracea L. cv. Marathon) or Japanese pachysandra (Pachysandra terminalis Siebold & Zucc)., negligible amounts of foliar‐derived calcium diffused into the simulated rain solution, and there was virtually no neutralization of the pH 35 rain simulant present in the capillary. A discussion of these results with respect to previous methods of investigation and theoretical possibilities of ion diffusion and cuticular permeability is presented.
Cellulase production by the vesicular–arbuscular mycorrhizal fungus Glomus mosseae (Nicol. & Gerd.) Gerd. and Trappe
Authors: GARCIA‐GARRIDO J. M. , GARCIA‐ROMERA I. , OCAMPO J. A. 
Published: April 2006

summaryProduction of endoglucanase (EC 3.2.1.4) and exoglucanase (EC 3.2.1.91) enzymes was studied during penetration of the host and development of the vesicular‐arbuscular mycorrhizal (VAM) fungus, Glomus mosseae, in roots of lettuce (Lactuca sativa) and onion (Allium cepa). Endo‐ and exoglucanase activities increase in VAM plants at the beginning of entry‐point formation and arbuscule development. No relationship was found between the number of vesicles and endo‐ and exoglucanase activities. Extracts from spores and external mycelium of G. mosseae had endo‐ and exoglucanase activities. Some of the cellulase activities detected in VAM roots were attributed to the fungus, since endoglucanase activity found in the external mycelium of G. mosseae and in mycorrhizal root extracts showed the same electrophoretic mobility.