bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of dry‐deposited sulphur dioxide on fungal decomposition of angiosperm tree leaf litter I. Changes in communities of fungal saprotrophs
Authors: NEWSHAM K. K. , FRANKLAND JULIET C. , BODDY LYNNE , INESON P. 
Published: April 2006

summaryComparisons of the saprotrophic fungi isolated from ash (Fraxinus excelsiorL.), birch (Betulaspp.), hazel (Corylus avellanaL.), pedunculate oak (Quercus roburL.), sessile oak [Q. petraea(Mattuschka) Liebl.] and sycamore (Acer pseudoplatanusL.) leaf litters from three woodlands exposed to low, medium and high levels (c. 0.0→ 0.060μl l−1) of sulphur dioxide (SO2) showed that the composition of the fungal communities differed between sites. Fumigation of angiosperm tree leaf litters from the least and the most polluted site with environmentally‐realistic concentrations (0.010–0.030 μl1) of SO2for 16–68 wk in an open‐air field‐fumigation experiment resulted in marked changes in the composition of the fungal communities in the leaf litters, comparable with differences found between the woodland sites.Cladosporiumspp.,Epicoccutn nigrumLink,Fitsariumspp. andPhoma exiguaDesm. were less commonly isolated from leaf litters exposed to SO2, whereasConiothyrium quercinumSacc. var.glandicolaGrove,Cylindrocarpon orthosporum(Sacc.) Wollenw. andPenicilliumspp. were more frequently isolated from fumigated litters. However, few differences could be detected in the response to SO2of the mycofloras of leaf litters originating from different woodland sites. In general, SO2did not affect the total extent of fungal occupancy of the microsites in the litter, as fungal species which decreased in abundance on exposure to the gas appeared to be replaced in the litter by other species more tolerant to the gas. SO2therefore appeared to be selectively toxic to saprotrophic fungi isolated from these litters.
Nitrate and ammonium uptake by maize: adaptation during relief from nitrogen suppression
Authors: JACKSON W. A. , VOLK R. J. 
Published: April 2006

summaryInitial (0–1 h) net rates of nitrate and ammonium uptake from 200 μM NH4NO3 were progressively increased as 8‐d‐old maize (Zea mays L.) seedlings, grown on 5 mM nitrate, were exposed to nitrogen‐free solutions for up to 48 h. Further nitrogen deprivation to 72 h resulted in a decline in the nitrate uptake rate. Nitrate uptake rates of plants at all stages of nitrogen deprivation increased steadily during an 8 h exposure to 200 μM NH4NO3. The pattern of the response of ammonium uptake during the 8 h adaptation period was considerably different. In nitrogen‐replete plants the ammonium uptake rate increased steadily, but deprivation of nitrogen for 12 h and longer resulted in complex responses in which the initial rate was followed by a decline, a subsequent increase, and another decline.The responses of the nitrate uptake system are considered to reflect a lifting of the suppressive effects of nitrate and a product of nitrate assimilation during nitrogen deprivation, a concomitant degradation of an induced component of the nitrate uptake system during that time, and reinduction of the uptake system during the adaptation period. The responses of the ammonium uptake system are considered to reflect the interplay of suppression by a product of ammonium assimilation, the accumulation of root ammonium and associated ammonium efflux, and a stimulation by ammonium of its own uptake. As a consequence of the differential responses of the two uptake systems, nitrate and ammonium uptake rates were positively correlated, largely independent, or negatively correlated as the plants progressed through the 8 h adaptation period.
Root endophytes of lupin and some other legumes in Northwestern USA
Authors: O'DELL T. E. , TRAPPE J. M. 
Published: April 2006

summaryRoots of ten species ofLupinusand three other legumes collected from field soils were cleared, stained, and examined for fungal colonization. Three species were not colonized. Nine species were colonized by aseptate hyphae and vesicles attributable to vesicular‐arbuscular mycorrhizal fungi. Seven species were sometimes colonized by fungi with septate hyphae, which often formed intracellular sclerotia. The associations observed are compared with previous reports and discussed in relation to legume systematics.
Chlorophyll fluorescence decay profiles of O3‐exposed spruce needles as measured by time‐correlated single photon counting
Authors: EVANS E. H. , BROWN R. G. , WELLBURN A. R. 
Published: April 2006

summaryChlorophyll fluorescence decay profiles have been measured in the wavelength range 680–720 nm for needles from Norway spruce [Picea abies (L.) Karst] trees which have been exposed to ozone. All profiles required three exponential components of lifetime 100–150 ps, 400–600 ps and 3.5–5.0 ns to fit the experimental data. Compared to control samples, the ozone‐treated needles exhibited a greater amount of the longest‐lived chlorophyll fluorescence and a redistribution in intensity for both the other components from 720 + to 690 nm. These observations are interpreted in terms of disruption of energy transfer and break‐up of light‐harvesting complexes on exposure to ozone. The potential for use of the technique in monitoring forest decline is discussed.
Nuclear magnetic resonance (NMR) microimaging of raspberry fruit: further studies on the origin of the image
Authors: GOODMAN B. A. , WILLIAMSON B. , CHUDEK J. A. 
Published: April 2006

summaryNuclear magnetic resonance (NMR) micro‐images of mature red raspberry (Rubus idaeus L.) fruits and their separated components have been produced under a variety of experimental conditions with the objective of understanding factors which determine image quality in different types of tissue. By varying the delay time between image accumulation sequences it has been shown that water molecules in drupelet surface layers in contact with other drupelets, and in the vascular bundles and traces in the receptacle and drupelets have shorter relaxation times than those in other tissues of the fruit. By performing separate T1‐ > and T2‐weighted imaging sequences it was shown that the short relaxation times in the vascular tissue was primarily a T1 effect. This is probably caused by paramagnetic ions because electron paramagnetic resonance (EPR) spectroscopy showed significant amounts of the manganese(n) ion in a spectrum of an aqueous extract of receptacle tissue. The cause of the short relaxation times in the drupelet surface layers is less clear, but we suggest that epicuticular waxes or the suberized cuticular layer of the epidermis might be responsible.The appearance of entire seeds, including the mature embryos, as featureless black regions in the images has been shown to be due to the lower concentration of mobile protons in these structures compared with that in the surrounding mesocarp, and not to differences in relaxation properties of the protons. Consequently, internal detail of the seeds could only be obtained by separating them from the fruit.
Exposure of spring wheat, Triticum aestivum L., cv. Drabant, to different concentrations of ozone in open‐top chambers: effects on the ultrastructure of flag leaf cells
Authors: OJANPERÄ K. , SUTINEN S. , PLEIJEL H. , SELLDÉN G. 
Published: April 2006

summarySpring wheat, Triticum aestivum L., cv. Drabant, was exposed to different concentrations of ozone in open‐top chambers for one growing season, at a site located in south‐west Sweden. The chambers were placed in a field of commercially grown spring wheat. The treatments were charcoal‐filtered air (CF), non‐filtered air (NF), non‐filtered air + 25 nl 1−1ozone (NF +) and non‐filtered air + 35 nl 1−1ozone (NF++). Ozone was added daily between 11.00 and 18.00 h, starting at anthesis. Fumigation with elevated concentrations of ozone caused chlorosis of the flag leaves. In the NF++ and NF+ treatments chlorosis appeared after 7 and 20 days of fumigation, respectively, and in the CF treatment after about 34 days, A progressive series of changes occurred in the mesophyll cells of the flag leaves after ozone fumigation. Starting at anthesis, the first changes occurred in the cytoplasm and involved a decrease in the amount of cytoplasm and an increase in the vacuolization of the cells. Subsequently the chloroplasts became affected decreasing in area and containing more plasto‐globuli. Finally vesicles were formed between the grana thylakoids and at the same time the plasma membrane came loose from the cell wall and convoluted. The mitochondria remained unaffected until only lipid droplets, oleosomes, were left in the cells. These changes were not specific for ozone as they occurred also in the CF treatment, although later in time. This indicates that ozone causes premature senescence in wheat flag leaves.
Long‐term effects of ozone and simulated acid rain on the foliage dynamics of slash pine (Pinus elliottii var. elliottii Engelm.)*
Authors: BYRES DAVID P. , DEAN THOMAS J. , JOHNSON JON D. 
Published: April 2006

summarySeedlings from four half‐sib families of Pinus elliottii var. elliottii Engelm. were planted in open‐top chambers, and exposed to ozone and simulated acidic precipitation. Treatments were applied for 11 months per year for 28 months. The ozone concentrations were: charcoal filtered air (CF), nonfiltered ambient air (1×), twice the nonfiltered level (2 ×) and three times the nonfiltered level (3 ×). Ozone exposures were computer controlled to follow natural diurnal fluctuations in ambient ozone concentrations. Simulated acid rain at pH 3.3, 4.3 or 5.3 was delivered weekly at the same volume as average weekly rainfall to all chambers.Leaf area, bud number and fascicle survival were all highest in the CF chambers. Genetic differences between half‐sib families were apparent in both leaf area and the number of live buds. Leaf area and fascicle survival were reduced with every increase in ozone exposure from CF to 3 ×. Leaf litterfall increased significantly with increasing ozone exposure. Leaf growth, measured by mean leaf area and mean dry weight per needle, was not affected by ozone exposure or by acid rain. It was concluded that ozone reduced leaf area mainly by causing premature leaf senescence.The only significant effect of acidic precipitation was enhanced leaf retention in trees irrigated with pH 3.3 solution. The results indicate that the increasing levels of trophospheric ozone may significantly reduce the growth of slash pine through foliage loss. The increased leaf retention caused by acid rain is unlikely to compensate for the detrimental effect of ozone.
Effects of nitrogen oxides on nitrate assimilation in bryophytes
Authors: MORGAN S. M. , LEE J. A. , ASHENDEN T. W. 
Published: April 2006

summaryNitrate assimilation and photosynthetic responses of Ctentdium mulluscum (Hedw.) Mitt. Homalothecium sericeum (Hedw.) Br.Eur. Pleurusium schreberi (Brid.) Mitt. Hylocomium splendens (Hedw.) Br.Eur. were studied during and after controlled exposures to 35 nl 1−1NO2 and 35 nl 1−1NO. NO2 induced nitrate reductase activity in all species 24 hours after the start of fumigation. The magnitude of the inductions varied between 23 and 89%. In contrast, exposure to NO caused a rapid decline in activity within 24 hours. After 21 days continuous exposure to each of the gases, the plants were supplied with a single application of 10 mM, NaNO3. Nitrate reductase activity was induced only in plants exposed to clean air. NO8exposure caused a loss of nitrate inducibility of NR. There were no marked effects on rates of oxygen evolution. After a three‐week pollution‐free period, the bryophytes regained the capacity for nitrate assimilation.
Isozymes in isolates of Suillus species from Pinus cembra L.
Authors: KELLER G. 
Published: April 2006

summaryIsolates of Suillus plorans (Roll.) Sing., Suillus placidus (Bon.) Sing, and Suillus sibiricus Sing. obtained from basidiocarps collected in two sub‐alpine forest regions were subjected to analysis of isozyme expression by means of horizontal starch gel electrophoresis. Four unknown strains isolated from tuberculate mycorrhizas of Pinus cembra L. were included in this study. Isozymes, expressed as individual bands, were reproducibly detected in mycelial extracts of 20, 11, and 2 isolates of S. plorans, S. placidus, and S. sibiricus, respectively. Isozyme banding patterns were diagnostic for each species and consistent for each strain tested. Isozyme electrophoresis is suitable for characterizing and fingerprinting individual isolates of Suillus species ectomycorrhizal with Pinus cembra. Enzyme assays for distinguishing between these species are recommended. Isolates from tuberculate mycorrhizas gave isozyme patterns that were consistent with S. plorans. Cluster analyses based on calculated similarity values of isozyme data demonstrated that intraspecific variability exists among isolates of S. plorans and S. placidus. Isozyme variability‐ was quite different in isolates of S. plorans from two different forest regions.
DNA topoisomerases in Gloeothece (Nägeli) sp. ATCC 27152: a role in N2 fixation?
Authors: Page T.S. , Gallon J. R. 
Published: April 2006

summaryExtracts from aerobically grown cultures of the unicellular cyanobacterium Gloeothece (Nägeli) sp. ATCC 27152 converted relaxed ColE1 plasmid cccDNA into a supercoiled form. They therefore contained a DNA gyrase. However, when DNA gyrase was inhibited, these same extracts catalyzed a net relaxation of ColE1 DNA, implying that they also contained an enzyme similar to DNA topoisomerase I. During the first 2 h after transfer of aerobically grown cultures of Gloeothece to an atmosphere of O2, the ability of extracts to generate supercoiled DNA was temporarily lost. Instead, extracts catalyzed net relaxation of ColE1 DNA during this period, which coincided with a transient inhibition of nitrogenase synthesis. O2 and some related compounds also inhibited DNA supercoiling by extracts of Gloeothece in vitro. As in other diazotrophs therefore, O2 may inhibit nitrogenase synthesis in Gloeothece by altering the relative activities of DNA gyrase and DNA topoisomerase I in such a way that relaxation of one or more of the nif genes may occur, with consequent inhibition of transcription. However, this effect is only transient. In contrast, addition of NH4+ to cultures of Gloeothece permanently inhibited nitrogenase synthesis and did not abolish the ability of extracts to catalyze net supercoiling of DNA. Moreover, NH4+ did not abolish DNA supercoiling in vitro. NH4+ therefore appears to inhibit nitrogenase synthesis in Gloeothece by a mechanism different from that of O2.
The late Quaternary vegetational history of northwest Greece
Authors: Willis K.J. 
Published: April 2006

summaryThe mountainous region of northwest Greece has often been cited as a possible area for the existence of temperate tree taxa during the last glacial. This series of papers examines the vegetational history and sedimentary history of two small basins in the Pindus mountain range of northwest Greece. The two basins are 18 km apart but at contrasting heights of 285 and 1800 m. The present paper describes results from the lowland basin of Gramousti lake. Techniques of pollen analysis, plant macrofossil analysis, sediment chemistry, mineral magnetics and radiocarbon dating are employed to reconstruct both the vegetational and sedimentary history of the basin. The sequence extends c. 14000 bp to c. 1000 bp. Palaeobotanical studies suggest that, during the lateglacial, vegetation in this lowland region was dominated by herbaceous taxa indicative of an open environment. Of the trees, only Quercus and Pinus were present, in low numbers. The lateglacial/postglacial transition was represented by an expansion of oak woodland and a reduction in steppe vegetation. Quercus dominated woodland persisted throughout much of the postglacial and became more diverse at c. 7500 bp with the arrival and expansion of Carpinus orientalis/Ostrya carpinifolia. Anthropogenic intervention at c. 4500 bp was probably responsible for a reduction in the oak woodland and the formation of a vegetation type similar to present day which is dominated by herbaceous taxa and chew‐resistant shrubs such as Quercus coccifera and Paliurus spina‐christi.
The late Quaternary vegetational history of northwest Greece
Authors: WILLIS K.J. 
Published: April 2006

summaryGramousti lake and Rezina marsh are small basins, of similar size, 20 km apart but at contrasting heights of 285 and 1800 m. Comparison of the palaeoecological and sedimentary sequences from the two sites indicates that in the early postglacial, there was distinct altitudinal zonation of the vegetation. In the mountains, a dense mixed woodland containing at least sixteen different tree taxa became established whereas the lowland vegetation consisted of an open oak woodland which was much less diverse. It is suggested that the differences seen between the two sites is evidence for the existence of a montane refugium for temperate tree taxa during the lateglacial. The great contrast over such a small spatial distance suggests that refugia were probably small pockets of vegetation in micro‐environmentally favourable locations, for example, the more humid mountains. Throughout the first 5000 yr of the postglacial, the contrast in vegetation around the two sites persisted and it was not until c. 6000 BP that the ‘warm‐stage’ refugium in the mountains became reduced in diversity and density. Finally, the onset of anthropogenic disturbance at c. 4000 BP resulted in the total depletion of the montane forest and the dominance of a herbaceous vegetation at both sites.
Synonymy of the three apparent isoenzymes of 3‐deoxy‐D‐arabino‐heptulosonate 7‐phosphate synthase in Pisum sativum L. with 3‐deoxy‐d‐manno‐octulosonate 8‐phosphate synthase and the DS‐Co/DS‐Mn isoenzyme pair
Authors: DOONG R. L. , JENSEN R. A. 
Published: April 2006

summaryThree enzymes, capable of condensing phosphoenolpyruvate with erythrose 4‐phosphate, were separated by DEAE‐cellulose column chromatography of extracts from young leaves of Pisum sativum. One enzyme was identified as 3‐deoxy‐d‐manno‐octulosonate 8‐phosphate (KDOP) synthase (EC 4.1 .2.16). This novel plant enzyme mimicks 3‐deoxy‐D‐arabino‐heptulosonate 7‐phosphate synthase (EC 4.1 .2.15) in vitro by virtue of its substrate ambiguity. KDOP synthase used erythrose 4‐phosphate 28% as well as arabinose 5‐phosphate at high substrate concentrations. The pH optimum was 6.5 and divalent cations were neither required nor stimulatory. The remaining two enzymes possessed the distinctive properties of the DAHP synthase (DS) isoenzymes, DS‐Mn and DS‐Co, previously established in tobacco and spinach to be chloroplast‐ and cytosol‐localized isoenzymes, respectively. DS‐Mn was highly specific for its substrates, required dithiothreitol (a hysteretic activator) for activity, was stimulated 3.6‐fold by 0.5 mM Mn2+, and exhibited a pH optimum of 7.5. DS‐Co, by contrast, showed an extreme degree of substrate ambiguity (giving greater rates with glycolaldehyde and glyceraldehyde 3‐phosphate than with erythrose 4‐phosphate at saturating substrate concentrations), had an absolute requirement for a divalent metal, and exhibited a high pH optimum of 9.0 for catalysis.
Calcification and utilization of inorganic carbon by the coccolithophorid Emiliania huxleyi Lohmann
Authors: NIMER N. A. , MERRETT M. J. 
Published: April 2006

summaryThe relationship between inorganic‐carbon dependent photosynthetic oxygen evolution and calcification was investigated in high‐ and low‐calcifying strains of Emiliania huxleyi showing a ten‐fold difference in calcification rate. Unlike the low‐calcifying strain calcifying cultures showed a four‐fold increase in inorganic carbon (1 mM) dependent photosynthetic oxygen over the pH range 5‐8.3 resulting in a 20 fold difference in photosynthetic rate between the two strains at pH 8.3. Calcifying cells have a high affinity for HCO3−, the concentration of dissolved inorganic carbon [DIC] required for half‐maximal rate of photosynthetic O2 evolution (K0.5[DIC]) being 200 μM at pH 8‐3. In mid‐exponential phase cultures the stoichiometry between 14CO2 fixation and calcification was 1 : 1 so it is likely that the high photosynthetic rate at pH 8.3 is sustained by 14CO2, released from H 14CO2 during calcification.Measurement of bicarbonate transport by the silicone‐oil‐layer centrifugal filtering technique demonstrated a rapid uptake and achievement of equilibrium (less than 3 s) between the intracellular and external inorganic carbon concentrations in low and high‐calcifying cells. Subsequent metabolism of the 14C intracellular inorganic carbon pool did not occur in low‐calcifying cells suggesting the block in calcification occurs either in transport into or within the coccolith vesicle.
Partitioning of biomass and carbohydrates in field‐grown radish under ambient concentrations of ozone, and treated with the anti‐ozonant ethylene‐diurea (EDU)
Authors: KOSTKA‐RICK REINHARD , MANNING WILLIAM J. 
Published: April 2006

summaryThe use of an anti‐ozonant provides a potential way for assessing yield losses caused by oxidant air pollution, predominantly ozone (O3), in field‐grown crops without the need of enclosures like open‐top chambers. One major prerequisite for the soundness of this method is the absence of direct effects of the anti‐ozonant EDU (ethylenediurea) itself on plant growth at low concentrations of O3 pollution. This condition was tested for field‐grown cultivars of radish (Raphanus sativus L.) parallel with investigations on the influence of soil drench treatments with EDU on the partitioning of biomass and carbohydrates between shoot and sink organs, i.e. hypocotyl and fibrous root, under ambient amounts of atmospheric O3, pollution. During 9 staggered plantings in two years, radish cultivars of differential sensitivity to O3 were harvested at two‐day intervals from emergence until vegetative maturity. Mean relative growth rates (RGR) for both sink and shoot organs were compared between EDU‐treated and non‐treated plants.When the relative deviation in RGR between EDU‐treatments was regressed vs. the O3 exposure of corresponding time intervals, linear relationships were highly significant for the sink organs of all three cultivars tested. Significant decreases in RGR attributable to O3 occurred above thresholds of O3 exposure equivalent to 52‐58 nl l−1O3 (daily 7‐h mean). No significant alterations of RGR of shoots were observed due to O3. Shoot growth rate of one variety was slightly increased by EDU as was RGR of sink organs in two of the cultivars at low‐levels of O3.Amounts of soluble carbohydrates (TSC) increased with biomass accumulation of both shoot and sink organs, and starch content decreased. These patterns were more apparent in sink tissues than in shoots. No significant differences in carbohydrate partitioning between treatments or between cultivars were detected. The linear relationship between the sink‐to‐shoot ratios of biomass and total non‐structural carbohydrates (TNC) was highly significant. From the results it is suggested that sink‐to‐shoot patterns of TNC occur synchronously with or slightly precede the partitioning of biomass rather than lag behind it.