bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitrogen, phosphorus and potassium uptake and demand in Agrostis capillaris: the influence of elevated CO2 and nutrient supply
Authors: NEWBERY R. M. , WOLFENDEN J. , MANSFIELD T. A. , HARRISON A. F. 
Published: April 2006

SUMMARYResponses to elevated CO2 have been studied using Agrostis capillaris L., an upland grass which is abundant on nutrient‐poor soils. Plants were grown in sand culture with a wide range of nitrogen, phosphorus and potassium concentrations, and the impact of CO2 on the demand for nutrients was determined using isotopic root bioassays. Plants grown with the smallest concentrations of N and P showed typical foliar symptoms associated with deficiency of these elements. However, even when supplies of N and P were limiting to growth, additional CO2 (250 ppm above ambient) influenced neither total N nor total P in above‐ground tissues, nor nutrient demands as indicated by the bioassay. The estimates of the demand of the plants for K from the 86Rb bioassay indicated an appreciable increase when plants were raised in elevated CO2. For plants of the same size with the same nutrient supply, those grown in elevated CO2 consistently displayed an increased internal demand for K. Uptake of K was not however, enhanced by elevated CO2 even in non‐limiting conditions and it might therefore be limited by a factor other than K supply. The overall conclusion from the experiments is that when A. capillaris is grown in elevated CO2, uptake of N, P and K fails to increase proportionally with dry mass. This was true even when nutrient supplies were adequate, and it appears that nutrient‐use‐efficiency might increase to enable the plants to maintain growth in elevated CO2.
Field study of leaf photosynthetic performance by a Mediterranean deciduous oak tree (Quercus pubescens) during a severe summer drought
Authors: And C. DAMESIN , RAMBAL S. 
Published: April 2006

SUMMARYQuercus pubescensWilld. is a winter deciduous oak species which co‐occurs in the Mediterranean area with an evergreen oak,Q. ilex.As the knowledge ofQ. pubescensassimilation patterns is poorly documented, we monitored leaf physiological parameters throughout a growing season. In summer, drought was particularly severe, and some trees experienced pre‐dawn water potentials (Ψpd) as low as – 4·5 MPa. Diurnal courses of net photosynthesis, stomatal conductance and I photochemical efficiency of photosystem II (PS II) were recorded on four trees in the field. Maximum assimilation rates (10–16·5 μmol m−2s−1, depending on sampled trees) occurred in spring. Leaf carbon gain recovered in autumn even after water potential fell to – 3·4 MPa. During progressive drought, Ψpddecreased substantially, leaf gas exchange was reduced and showed an important diurnal depression. At – 2 MPa (Ψpd), net photosynthesis and stomatal conductance were still about 5 μmol m−2s−1and 50 mmol m−2s−1, respectively. Pre‐dawn maximal PS II photochemical efficiency was stable to – 4 MPa. The diurnal decrease in photochemical efficiency of PS II (Fv/Fm), measured after 30 min of dark adaptation, was enhanced during drought but maximal values always recovered at sunset, i.e. leaves only experienced short‐term reversible PS II inhibition induced by high light and temperature. In conclusion,Q. pubescensdisplays a strategy of tolerance to drought and an efficient protection against high irradiance.
Modelling pea (Pisum sativum) root growth in drying soil. A comparison between observations and model predictions
Authors: TSEGAYE TEZERA , MULLINS C. E. , DIGGLE A. J. 
Published: April 2006

SUMMARYPeas were grown in the glasshouse for 29 d in duplicate 1 m tall containers packed with soil at field capacity (a matric potential of –0·005 MPa) to a bulk density of 1·30 Mg m−3 and with an initial penetration resistance (PR) of 0·35 MPa. Counts of new root contacts on the sides of the containers and matric potential (Ψm) measurements at 0·1 m depth increments were made every two days. Although the plants were not watered, matric potential was never less than –0·041 MPa and was unlikely to have directly limited root growth, but it was used as a predictor of PR and hence of the effect of PR on root growth rate. The effect of PR on root growth was predicted using experimentally determined relationships between root growth rate and PR, and PR and Ψm. These results were used with the ROOTMAP root growth model to give two different model scenarios: (1) variable resistance (VR), allowing mechanical impedance to vary with time and depth in line with the observed values of Ψm and (2) constant resistance (CR), maintaining mechanical impedance at its value at the start of the experiment. CR predictions gave a gross overestimate of the rate at which new root contacts were made on the container walls, whereas VR predictions agreed with experimental observations to within the limits of accuracy of the model and the observations. The comparison between CR and VR predictions gives a clear demonstration of bow the increase in soil strength caused by roots drying the profile can result in a reduction in the size and extent of the whole root system.
Responses of pine needle endophytes to air pollution
Authors: HELANDER MARJO L. 
Published: April 2006

SummaryThe effects of heavy metals and sulphuric acid on pine needle endophytes were studied using gradient analyses, an experimental field study and an in vitro laboratory experiment. Gradient analyses were carried out near factory complexes at Harjavalta (southern Finland) and Monchegorsk (Kola peninsula, Russia); both factories emit heavy metals and sulphur. The experimental field plots had received copper (Cu) and nickel (Ni) treatment, sulphuric acid treatment, or a combination of the two, for 3 yr before sampling. Endophyute strains isolated 1 and 8 km from the factory were studied for their mental tolerance in the laboratory. The total number of needles infected with endophytes and also the number of needles infected with a specific endophyte, Cenangium ferrucinosum Fr.:Fr., were significantly lower near factories than at the control area. The frequency of the endophyte Hormonema sp., on the other hand, was not correlated with distance from the factory. In the experimental field study, the total number of endophyte‐infected needles was not affected by the treatments. The number of needles infected with Hormonema sp., however, was significantly lower in the Cu and Ni treated trees than in irrigated controls. Hormonema sp., strains isolated near the Harjavalta factory were more tolerant of Cu and Ni in vitro than were those isolated 8 km from the factory.
Exposure of spring wheat (Triticum aestivum) to ozone in open‐top chambers. Effects on acyl lipid composition and chlorophyll content of flag leaves
Authors: SANDELIUS ANNA STINA , NÄSLUND KRISTINA , CARLSSON ANDERS S. , PLEIJEL HÅKAN , SELLDÉN GUN 
Published: April 2006

SUMMARYSpring wheat (Triticum aestivumL. cv. Drabant) was exposed to different concentrations of ozone in open‐top chambers in a field of commercially grown wheat. The following treatments were used: charcoal‐filtered air (CF), non‐filtered air (NF) and non‐filtered air supplemented with 25 nl 1−1 ozone (NF+) and 35 nl 1−1 ozone (NF ++) for 7 h d−1. Flag leaves were analysed for chlorophyll content, total fatty acid composition and fatty acid compositions and contents of monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), phosphatidylcholine (PC) and phosphatidylethanolamine (PE). The chlorophyll content decreased significantly with time and ozone concentration. After 4 wk of exposure, the content of MGDG was significantly lower in flag leaves from the N F ++ treatments than in those from the other treatments. The contents of DGDG and PC also decreased while that of PE increased, although these changes were not statistically significant. In the total lipid extract the proportion of 18:3 decreased with time and ozone concentration. Similar changes occurred in MGDG 18:3 at a later stage. Using the concept of accumulated exposure over threshold (AOT), it was evident that the parameters studied differed in ozone sensitivity. After 4 wk of exposure, the best linear dose‐response relationships between accumulated exposure and chlorophyll as well as MGDG contents were obtained with a threshold ozone concentration of 30 nl l−1. For total lipid 18:3 and MGDG 18:3 the corresponding thresholds were 40 and 50 nl 1−1, respectively. Furthermore, the sensitivity to ozone, expressed as loss of chlorophyll, increased with increasing flag leaf age. In leaves exposed for 7, 13 and 20 d, the best linear fits were obtained with AOT50, AOT40 and AOT30, respectively. In conclusion, ozone sensitivity increased with flag leaf age and different membrane constituents were differently sensitive to ozone. The results support previous suggestions that ozone causes premature senescence in wheat flag leaves.
A process‐oriented explanation of the nonlinear relationship between grain yield of wheat and ozone exposure
Authors: PLEIJEL HÅKAN , SKÄRBY LENA , WALLIN GÖRAN , SELLDÉN GUN 
Published: April 2006

SUMMARYA model for the impact of ozone on grain yield in spring wheat (Triticum aestivum L.) was constructed. The mode was based on the observations in the literature as well as in the present experiment, that the productivity of the above‐ground biomass and the carbon partitioning of the above‐ground biomass do not respond to ozone above the same threshold concentrations. The model was applied to a data set in which spring wheat was exposed to different ozone concentrations in open‐top chambers. It was concluded that the nonlinearity of a simple dose‐response curve for grain yield can be explained in terms of the product of two linear responses: (1) the response of total above‐ground biomass to an ozone dose above 10 nl 1−1, and (2) the response of the harvest index to an ozone dose above 40 nl 1−1 The nitrogen content of the grain increased linearly with the dose above 40 nl 1−1.It is hypothesized that the effect of comparatively small ozone concentrations on total above‐ground biomass is caused by a reduction of leaf duration by ozone, and that the effect on carbon partitioning is caused by ozone affecting the sink capacity or activity of the growing grain. The maximum coefficients of determination (r2) for the linear regression between grain yield and accumulated ozone dose above thresholds in the range of 0–70 nl 1−1, were never as great as those for total above‐ground biomass and harvest index. Nevertheless, statistically significant linear regressions were obtained for the thresholds 20, 30 and 40 nl 1−1, the highest correlation being with 30 nl 1−1 Thus, it seems acceptable to use linear regressions between grain yield and the accumulated dose, although these do not take into direct account the complexity of the effects of ozone on wheat.
Determinations of dye diffusivities in the cell‐wall apoplast of roots by a rapid method
Authors: BAYLISS C. , VAN DER WEELE C. , CANNY M. J. 
Published: April 2006

summaryA method is described of measuring dye diffusivity through the cell‐wall apoplast of roots, using sections of fresh material cut by hand under paraffin oil. Root pieces of Vicia faba and Glycine max were immersed in a solution of sulphorhodamine G for short periods, and the advance of the dye through the cell‐wall apoplast was measured, either in a number of sections cut after various periods of diffusion, or by photographing the same section at intervals while diffusion into it from the surface was observed under the microscope. Fick's second law was used to estimate the diffusivity. Diffusivities, expressed relative to the diffusivity in water (Daq) were in the range Daq/16 to Daq/55 for Vicia roots. The values for Glycine roots showed a wide scatter, with a modal value of Daq/1700. Comparison of this rapid method with the much more laborious stabilization of the dye by freeze‐substitution confirmed the values of measured diffusivities in Vicia.
Morphological and biochemical characterization of spikelet development in naked oats (Avena sativa)
Authors: OUGHAM HELEN J. , LATIPOVA GALINA , VALENTINE JOHN 
Published: April 2006

summaryThe dominant gene N‐1 in cultivated oats gives rise to a phenotype characterized by a thin papery lemma from which the grain readily threshes free, a multiflorous habit, and rachillas that are elongated in comparison to those of husked oats. This study was undertaken in order to identify the stages at which morphological and biochemical development of naked and husked oats begin to diverge, and to look for correlated differences in gene products (mRNAs and proteins). Spikelet morphology in naked and husked oats was shown to diverge early in panicle development: the first visible difference was premature cessation of growth of the third and subsequent florets in husked oats. Lignin deposition in the lemma occurred later and followed a similar time‐course in both genotypes, though in naked oats it was restricted to the vascular bundles. Mature lemmas of the naked genotype closely resembled glumes in appearance and in lignification pattern. Genotypic differences in extractable polypeptide complements were apparent only late in development, coinciding with the onset of lignification, and were not associated with comparable differences in translatable mRNA profiles. The normal (n‐1) allele at the naked locus is likely to encode a transcription factor with properties similar to those of previously‐characterized homeotic gene products in plants.
Lead phytoextraction: species variation in lead uptake and translocation
Authors: HUANG J. W. , CUNNINGHAM S. D. 
Published: April 2006

summaryLead transport has been characterized in corn (Zea mays L. cv. Fiesta) and ragweed (Ambrosia artemisiifolia L.), and the Pb phytoextraction efficiency of these species has been compared with that of Tritiaim aestivum, Thlaspi rotundifolium, Thlaspi caerulescens and Brassica juncea, using both nutrient solutions and Pb‐contaminated soils. Our results demonstrated that plant species differ significantly in Pb uptake and translocation. In short term (60 min) experiments, Pb uptake by ragweed roots was threefold higher than that by corn roots. After 2 wk of Pb (100/yM) exposure in hydroponics, root‐Pb concentration was 24000 mg kg−1 for ragweed and 4900 mg kg−1 for corn. In contrast to root‐Pb concentration, shoot‐Pb concentration was significantly higher in corn (560 mg kg−1) than in ragweed (30 mg kg‐1). At an external Pb concentration of 20/IM, corn concentrated Pb in shoots by 90‐fold, and ragweed concentrated Pb in shoots by 20‐fold over the solution Pb concentration. Of the 11 species/cultivars tested using both nutrient solutions and Pb‐contaminated soils, corn accumulated the highest shoot‐Pb concentration. Using this corn cultivar, we investigated the role of synthetic chelates in Pb phytoextraction. Addition of HEDTA (2.0 g kg−1 soil) to a Pb‐contaminated soil (total soil Pb 2500 mg kg−1) resulted in a surge of Pb accumulation in corn. The shoot Pb‐concentration was increased from 40 mg kg−1 for the control (‐HEDTA) to 10600 mg kg−1 for the HEDTA‐treated soil. To our knowledge, this is the highest shoot Pb concentration reported in the literature for plants grown on Pb‐contaminated soils. Our results suggest that in combination with sou amendment, some agronomic crops, such as corn, might be used for the clean‐up of Pb‐contaminated soil.
Decomposition, nitrogen and phosphorus mineralization from beech leaf litter colonized by ectomycorrhizal or litter‐decomposing basidiomycetes
Authors: COLPAERT JAN V. , VAN TICHELEN KATIA K. 
Published: April 2006

summaryThe decomposition and the nitrogen and phosphorus mineralization of fresh beech (Fagus sylvatica L.) leaf litter are described. Leaves were buried for up to 6 months in plant containers in which Scots pine (Pinus sylvestris L.) seedlings were cultivated at a low rate of nutrient addition. The saprotrophic abilities of three ectomycorrhizal fungi, Thelephora terrestris Ehrh.: Fr., Suillus bovinus (L.: Fr.) O. Kuntze and Paxillus involutes (Batsch: Fr) Fr., were compared with the degradation caused by the litter‐decomposing basidiomycete, Lepista nuda (Bull.: Fr.) Cooke. Uninoculated leaves were included as controls. The investigation was performed at two different pH values since substrate pH is supposed to have an effect on the activities of extracellular enzymes of ectomycorrhizal fungi. The enzyme expression might also be largely influenced by the substrate they colonised. The mycorrhizal fungi caused only a low decomposition rate of the litter compared with that of L. nuda, and nitrogen was released only by L. nuda. Leaves colonized by mycorrhizal fungi showed no net release of nitrogen; on the contrary, a small accumulation of N in the litter was observed. It therefore seems likely that the ectomycorrhizal fungi studied do not have the ability to decompose efficiently the lignocellulose matrix of the relatively recalcitrant beech leaf litter. The degradation of this matrix seems to be essential for the fungi to gain access to the leaf nitrogen pool of fresh beech litter. A direct release of nitrogen from organic compounds by ectomycorrhizal fungi seems therefore to be confined to the older litter layers. The beech leaf litter contained an important fraction of easily mineralizable phosphorus. P was not a growth limiting factor m the cultivation system, and could therefore accumulate in the leaf litter colonized by the ectomycorrhizal mycelium.
Tissue localization of u.v.‐B‐screening pigments and of chalcone synthase mRNA in needles of Scots pine seedlings
Authors: SCHNITZLER JÖRG‐PETER , JUNGBLUT TIM P. , HELLER WERNER , KÖFFERLEIN MATTHIAS , HUTZLER PETER , HEINZMANN ULRICH , SCHMELZER ELMON , ERNST DIETER , LANGEBARTELS CHRISTIAN , SANDERMANN HEINRICH 
Published: April 2006

summaryEpidermal tissue was isolated from Scots pine (Pinus sylvestris L.) needles by enzymatic digestion in order to study tissue distribution of u‐V.‐B‐screening pigments. Up to 90% of the needle content of a group of diacylated flavonol glycosides that were structurally closely related was found in the epidermal layer. Among these metabolites, 3″,6″‐di‐paia‐coumaroyl‐isoquertitrin and 3″,6″‐di‐para‐di‐coumaroyal‐astragalin were the main u.v.‐B‐induced compounds in cotyledons and primary needles, respectively. However, catechin and astragalin (kaempferol 3‐glucoside), two non‐acvlated flavonoid metabolites, were only observed in total needle extracts, and at levels independent of u.v.‐B treatment. According to this metabolite distribution, the mRNA of chalcone synthase, the key enzyme to flavonoid, was found in epidermal and mesophyll as well as vascular tissues. The major alkali‐extractable wall‐bound phenolic metabolites, astragalin, 4‐coumaric acid, and ferulic acid, a minor component of the cell wall, were also found exclusively in the epidermal layer. These compounds were not stimulated by u.v.‐B irradiation within the experimental period. Staining of needle cross sections and epidermal layer preparations with Naturstoffreagenz A confirmed the specific localization of wall‐bound astragalin in the outer wall of the epidermal layer. Model calculations of u.v.‐B absorptions at 300 nm of soluble and cell‐wall‐bound metabolites of the epidermal layer revealed an almost complete shielding of the mesophyll tissue From u.v.‐B radiation.
Investigating microclimatic influences on ozone injury in clover (Trifolium subterraneum) using artificial neural networks
Authors: BALLS G. R. , PALMER‐BROWN D. , SANDERS G. E. 
Published: April 2006

summaryMicroclimatic factors interact during ozone episodes to influence the sensitivity of plants to ozone and thus are likely Co modify the amount of injury development. This paper investigates these interactions in an ozone‐sensitive cultivar of clover (Trifolium subterraneum cv. Geraldton). Experiments were conducted using a glasshouse‐based closed‐chamber exposure system in which the plants were exposed for 7 h to either charcoal‐filtered air (CF) or CF plus ozone at concentrations ranging from 40 to 160 ppb. The microclimatic conditions inside the chambers ranged from 16 to 36 C, 0‐9‐3‐6 kPa vapour pressure deficit (VPD), and 80–460 μmol m−2s−1Photosynthetically Active Radiation (PAR). Seven days after ozone exposure, the extent of foliar ozone injury was scored visually. The assessment scoring system was validated by pigment analysis. The data from these exposures were analysed using artificial neural networks (ANNs), the principles of which are described in the paper. Two ANNs were used, one to investigate the effects of microclimate on the threshold AOT40 (dose accumulated above a threshold of 40 ppb) above which injury developed, the other to determine the extent of visible injury development. Both networks used temperature. VPD, PAR and AOT40 as inputs. Testing with previously unseen data showed that the networks produced accurate predictions of the threshold and extent of injury for a range of ozone doses and microclimatic conditions. For example, the injury score network predicted that at 100 μmol m2s1PAR and 1 kPa VPD an AOT40 of 150 ppb h was required to produce an injury score of 1, whereas in conditions of 400 μmol m−2s−1s′ PAR and 3.5 kPa VPD, an AOT40 of 460 ppb h was required. Analysis of the weightings of components of the trained networks indicated that VPD and PAR had a stronger influence on the response to ozone than did temperature. Furthermore, this approach revealed that microclimate had a greater influence on the extent of ozone injury than on the threshold for injury.
Nitrogen source regulates the biosynthesis of NADP‐glutamate dehydrogenase in the ectomycorrhizal basidiomycete Laccaria bicolor
Authors: LORILLOU SOPHIE , BOTTON BERNARD , MARTIN FRANCIS 
Published: April 2006

summaryNADP‐glutamate dehydrogenase (NADP‐GDH) is a key enzyme of N assimilation in ectomycorrhizal fungi, but little is known about its regulation. In the present study. the effects of N source and concentration cm NADP‐GDH specific activity, polypeptide content and biosynthesis have been investigated in the ectomycorrhizal basidiomycete Laccaria bicolor S238N. Mycelium was transferred from NH+4‐rich medium to either NO−3‐rich or N‐free medium. Under both these conditions, intracellular NH.−3 and glutamine content decreased dramatically. The specific activity of NADP‐GDH was simultaneously increased 3 4.5‐fold. Immunological analysis using anti‐GDH antibodies showed that depression of enzyme activity resulted from increased concentration of the GDH polypeptide. In addition, assessment of the steady‐state biosynthesis of NADP‐GDH by in vivo labelling of proteins demonstrated that the observed changes in enzyme concentration are explained by differences in the relative rate of enzyme biosynthesis. These results suggested that the source of N regulates synthesis of NADP‐GDH and that this regulation is under transitional and/or transcriptional control.