bluuebunny/crossref_metadata_2025 huggingface dataset:
The aquaporin‐4 water channel and brain tumour oedema
Authors: Saadoun S. , Papadopoulos M. C. , Bell B. A. , Krishna S. , Davies D. C.
Published: March 2003

Aquaporin‐4 (AQP4) is a water channel protein that is expressed by perimicrovessel astrocyte foot processes in normal brain. There is up‐regulation of astrocyte AQP4 mRNA in areas of the rat brain where the blood brain barrier is disrupted following focal brain ischaemia or physical injury. In contrast AQP4 knockout mice show less brain swelling and improved survival rates after water intoxication or focal cerebral ischaemia compared to wild type mice. However little is known about the expression of AQP4 in aggressive human brain tumours, even though they result in peritumoural oedema. Therefore formalin fixed samples of morphologically normal human brain (n = 5), astrocytomas (n = 10) and adenocarcinoma metastases to brain (n = 5) were embedded in paraffin wax, sections cut and investigated by AQP4 immunocytochemistry. These samples were obtained from patients who underwent craniotomy at Atkinson Morley’s Hospital during 1998–9. Immunolabelling was performed using a polyclonal AQP4 antibody (AB3068, Chemicon), visualised with immunoperoxidase and diaminobenzidine hydrochloride. Blood–brain barrier opening was visualised preoperatively, using contrast enhancement on computed tomography. AQP4 immunolabelling was confined to astrocyte foot processes surrounding microvessels in the 5 samples of normal brain and 5 low grade (Daumas‐Duport I or II) astrocytomas. In 4/5 high grade (Daumas‐Duport III or IV) astrocytomas there was strong immunolabelling over the cytoplasm of most tumour cells and/or reactive astrocytes that was not restricted to the perimicrovessel region. Up‐regulation of AQP4 immunoreactivity was also found in astrocytes adjacent to the 5 metastatic adenocarcinomas investigated. There was a significant correlation between up‐regulation of AQP4 immunolabelling and contrast enhancement on computed tomographs (P < 0.0001 Fisher exact). Therefore oedematous aggressive brain tumours and surrounding tissues demonstrate massive up‐regulation of expression of the water channel protein AQP4. The strong correlation between the presence of brain oedema and AQP4 expression suggests that AQP4 expression is intimately involved in the pathophysiology of tumour related brain oedema. However, it is not clear whether AQP4 is involved in the accumulation or clearance of brain oedema fluid.
The structural basis of pulmonary hypertension in chronic lung disease: remodelling, rarefaction or angiogenesis?
Authors: Hopkins Natalie , McLoughlin Paul
Published: March 2003

Chronic lung disease in humans is frequently complicated by the development of secondary pulmonary hypertension, which is associated with increased morbidity and mortality. Hypoxia, inflammation and increased shear stress are the primary stimuli although the exact pathways through which these initiating events lead to pulmonary hypertension remain to be completely elucidated. The increase in pulmonary vascular resistance is attributed, in part, to remodelling of the walls of resistance vessels. This consists of intimal, medial and adventitial hypertrophy, which can lead to encroachment into and reduction of the vascular lumen. In addition, it has been reported that there is a reduction in the number of blood vessels in the hypertensive lung, which could also contribute to increased vascular resistance. The pulmonary endothelium plays a key role in mediating and modulating these changes. These structural alterations in the pulmonary vasculature contrast sharply with the responses of the systemic vasculature to the same stimuli. In systemic organs, both hypoxia and inflammation cause angiogenesis. Furthermore, remodelling of the walls of resistance vessels is not observed in these conditions. Thus it has been generally stated that, in the adult pulmonary circulation, angiogenesis does not occur. Prompted by previous observations that chronic airway inflammation can lead to pulmonary vascular remodelling without hypertension, we have recently shown, using quantitative stereological techniques, that angiogenesis can occur in the adult pulmonary circulation. Pulmonary angiogenesis has also been reported in some other conditions including post‐pneumonectomy lung growth, metastatic disease of the lung and in biliary cirrhosis. Such angiogenesis may serve to prevent or attenuate increased vascular resistance in lung disease. In view of these more recent data, the role of structural alterations in the pulmonary vasculature in the development of pulmonary hypertension should be carefully reconsidered.
Congenital talipes equinovarus (clubfoot): a disorder of the foot but not the hand
Authors: Miedzybrodzka Zosia
Published: March 2003

Idiopathic (non‐syndromic) congenital talipes equinovarus, or clubfoot, is a poorly understood but common developmental disorder of the lower limb, which affects at least 2 per 1000 Scottish births (ISD data). It is defined as a fixation of the foot in a hand‐like orientation – in adduction, supination and varus – with concomitant soft tissue abnormalities. Despite advances in treatment, disability often persists. The aetiology of the condition has been little studied and is poorly understood. Neurological, muscular, bony, connective tissue and vascular mechanisms have been proposed, but the only firm evidence is that the mildest cases appear to be associated with intra‐uterine posture. There is evidence for a genetic contribution to congenital talipes equinovarus aetiology. Its incidence varies with ethnic group, and we found that a family history is present in 24–50% of cases, depending on the population studied. Complex segregation analysis suggests that the most likely inheritance pattern is a single gene of major effect operating against a polygenic background. Possible mechanisms for congenital talipes equinovarus are discussed.
Detection of symbiosis‐related polypeptides during the early stages of the establishment of arbuscular mycorrhiza between Glomus mosseae and Pisum sativum roots
Authors: SAMRA ASSEM , DUMAS‐GAUDOT ELIANE , GIANINAZZI SILVIO
Published: March 2003

Changes in polypeptide contents following inoculation of roots of Pisum sativum L. (wild type cv. Frisson (myc+, nod+)) with the arbuscular mycorrhizal fungus Glomus mosseae were analysed by two–dimensional gel electrophoresis (2D‐PAGE). A different polypeptide pattern was obtained in a mycorrhiza–resistant pea genotype P2 (myc+, nod−) inoculated with G. mosseae. In order further to characterize the polypeptide modifications detected and to provide evidence for some possible symbiosis–related (SR) proteins, a time course experiment, from appressoria formation to fully developed symbiosis, was carried out on two genotypes allowing fungal colonization: the wild type and its isogenic mutant P56 (myc+, nod−). The same experiment was done with the mycorrhiza‐resistant pea genotype (myc+, nod−). After G. mosseae inoculation, we characterized 12 additional polypeptides in the two mycorrhiza‐compatible pea genotypes which were never observed in root extracts from the mycorrhiza‐resistant mutant. Five polypeptides were first detected in the early stage of the symbiosis (5 d of inoculation) while others were observed later (8 d of inoculation). The induction and accumulation of these polypeptides seem to be more correlated to the establishment of the functional symbiosis than to the recognition stages and appressorium formation. Furthermore, none of the additional polypeptides were detected in the mycorrhiza‐resistant pea genotype. This mutant was more characterized by a great repression of polypeptides. In addition, up‐regulated and down‐regulated polypeptides from the mycorrhiza‐compatible genotypes were different from those of the mycorrhiza‐resistant genotype.
Growth and mycorrhizal colonization of three North American tree species under elevated atmospheric CO2
Authors: GODBOLD DOUGLAS L. , BERNTSON GLENN M. , BAZZAZ F. A.
Published: March 2003

summary

We investigated the effect of elevated CO2 on the growth and mycorrhizal colonization of three tree species native to north‐eastern American forests (Betula papyrifera Marsh., Pinus strobus L. and Tsuga Canadensis L. Carr). Saplings of the tree species were collected from Harvard Forest, Massachusetts, and grown in forest soil under ambient (c. 375 ppm) and elevated (700 ppm) atmospheric CO., concentrations for 27–35 wk.

In all three species there was a trend to increasing whole‐plant, total‐root and fine‐root biomass in elevated CO2, and a significant increase in the degree of ectomycorrhizal colonization in B. papyrifera and P. strobus, but not in T. Canadensis. However, in T, Canadensis the degree of colonization with arbuscular mycorrhizas increased significantly. In both the ambient and elevated environments, on the roots of B. papyrifera and P. strobus 12 distinct ectomycorrhizal morphotypes were identified. Distinct changes in the ectomycorrhizal morphotype assemblage of B. papvrifera were observed under CO2 enrichment. This change resulted in an increase in the frequency of ectomycorrhizas with a higher incidence of emanating hyphae and rhizomorphs, and resulted in a higher density of fungal hyphae in a root exclusion chamber.
Qualitative and quantitative changes in plant nitrogen acquisition induced by anthropogenic nitrogen deposition
Authors: NÄSHOLM TORGNY
Published: March 2003

Because nitrogen is the mineral nutrient needed in largest amounts by plants, it is usually also the limiting factor for plant growth in terrestrial ecosystems (Vitousek & Howarth, 1991). Consequently, the deposition of oxidized and reduced N compounds will almost invariably have large effects in these systems, and because N availability not only regulates plant growth but also that of organisms at other trophic levels, disturbances of several ecosystem processes might occur. The alternations introduced by deposition of atmospheric N compounds are both of a quantitative and of a qualitative nature. Moreover, N deposition can have phytotoxic as well as growth‐stimulating effects.

This short commentary gives a personal view of some of the possible consequences of N deposition on plants. It refers particularly to the oral presentations given by Professor Heinz Rennenberg and Dr Marta Peréz‐Soba, and to the discussions held after their talks where appropriate. Separate attention is given to four different consequence of anthropogenic N‐deposition: N‐availability; N‐form, N‐uptake by the shoot, and the period of N‐uptake. Finally, I have tried to adopt an ecosystem perspective and discuss briefly the concept of critical loads of N.
Nitrogen deposition and its contribution to nitrogen cycling and associated soil processes
Authors: GOULDING K. W. T. , BAILEY N. J. , BRADBURY N. J. , HARGREAVES P. , HOWE M. , MURPHY D. V. , POULTON P. R. , WILLISON T. W.
Published: March 2003

Human activity has greatly perturbed the nitrogen cycle through increased fixation by legumes, by energy and fertilizer production, and by the mobilization of N from long‐term storage pools. This extra reactive N is readily transported through the environment, and there is increasing evidence that it is changing ecosystems through eutrophication and acidification. Rothamsted Experimental Station, UK has been involved in research on N cycling in ecosystems since its inception in 1843. Measurements of precipitation composition at Rothamsted, made since 1853, show an increase of nitrate and ammonium N in precipitation from 1 and 3 kg N ha−1 yr−1, respectively, in 1855 to a maximum of 8 and 10 kg N ha−1 yr−1 in 1980, decreasing to 4 and 5 kg N ha−1 yr−1 today. Nitrogen inputs via dry deposition do, however, remain high. Recent measurements with diffusion tubes and filter packs show large concentrations of nitrogen dioxide of c. 20 μg m−3 in winter and c. 10 μg m−3 in summer; the difference is linked to the use of central heating, and with variations in wind direction and pollutant source. Concentrations of nitric acid and particulate N exhibit maxima of 1·5 and 2 μg m−3 in summer and winter, respectively. Concentrations of ammonia are small, barely rising above 1 μg m−3.

Taking deposition velocities from the literature gives a total deposition of all measured N species to winter cereals of 43·3 kg N ha−1 yr−1, 84% as oxidized species, 79% dry deposited. The fate of this N deposited to the very long‐term Broadbalk Continuous Wheat Experiment at Rothamsted has been simulated using the SUNDIAL N‐cycling model: at equilibrium, after 154 yr of the experiment and with N deposition increasing from c. 10 kg ha−1 yr−1 in 1843 to 45 kg ha−1 yr−1 today, c. 5% is leached, 12% is denitrified, 30% immobilized in the soil organic matter and 53% taken off in the crop. The ‘efficiency of use’ of the deposited N decreases, and losses and immobilization increase as the amount of fertilizer N increases. The deposited N itself, and the acidification that is associated with it (from the nitric acid, ammonia and ammonium), has reduced the number of plant species on the 140‐yr‐old Park Grass hay meadow. It has also reduced methane oxidation rates in soil by c. 15% under arable land and 30% under woodland, and has caused N saturation of local woodland ecosystems: nitrous oxide emission rates of up to 1·4 kg ha−1 yr−1 are equivalent to those from arable land receiving >200 kg N ha−1 yr−1, and in proportion to the excess N deposited; measurements of N cycling processes and pools using 15N pool dilution techniques show a large nitrate pool and enhanced rates of nitrification relative to immobilization. Ratios of gross nitrification∶gross immobilization might prove to be good indices of N saturation.
Nitrogen deposition: a component of global change analyses
Authors: NORBY RICHARD J.
Published: March 2003

The global cycles of carbon and nitrogen are being perturbed by human activities that increase the transfer from large pools of non‐reactive forms of the elements to reactive forms that are essential to the functioning of the terrestrial biosphere. The cycles are closely linked at all scales, and global change analyses must consider C and N cycles together. The increasing amount of N originating from fossil fuel combustion and deposited to terrestrial ecosystems as nitrogen oxides could increase the capacity of ecosystems to sequester C, thereby removing some of the excess carbon dioxide from the atmosphere and slowing the development of greenhouse warming. Several global and ecosystem models have calculated the amount of C sequestration that can be attributed to N deposition, based on assumptions about the allocation of N among ecosystem components with different C∶N ratios. They support the premise that, since industrialization began, N deposition has been responsible for an increasing terrestrial C sink, but there is great uncertainty whether ecosystems will continue to retain exogenous N. Whether terrestrial ecosystems continue to sequester additional C will depend in part on their response to increasing concentrations of atmospheric carbon dioxide, widely thought to be constrained by limited N availability. Ecosystem models generally support the conclusion that responses to increasing concentrations of carbon dioxide will be greater, and the range of possible responses will be wider, in ecosystems where increased N inputs originate as atmospheric deposition. The interactions between N deposition and increasing carbon dioxide concentrations could be altered considerably, however, by additional factors, including N saturation of ecosystems, changes in community composition, and climate change. Nitrogen deposition is also linked to global change issues through the volatile losses of nitrous oxide, which is a potent greenhouse gas, and the role of nitrogen oxides in the production of tropospheric ozone, which could interact with plant responses to elevated carbon dioxide. Any consideration of the role of N deposition in global change issues must also balance the projected responses against the serious detrimental impact of excess N on the environment.
The biology of mycorrhiza in the Ericaceae. XX. Plant and mycorrhizal necromass as nitrogenous substrates for the ericoid mycorrhizal fungus Hymenoscyphus ericae and its host
Authors: KERLEY SIMON J. , READ DAVID J.
Published: March 2003

In the ‘F’ horizons of acid mor‐humus soils of heathland ecosystems, mycorrhizal roots of the dominant ericaceous species form a large fraction of the soil biomass. Rapid turnover of these roots provides the potential for recycling of substantial amounts of nitrogen contained in their fungal and plant components. Here, we first determine the amount of N in the biomass of ericoid roots growing in heathland and show it to constitute a large proportion of total soil N. In order to assess the accessibility of this N to ericaceous plants, experiments were then conducted using aseptically produced shoot and root necromass of Vaccinium macrocarpon Ait., the roots being grown with or without mycorrhizal colonization. These materials were provided as sole nitrogenous substrates in growth experiments using the ericoid mycorrhizal fungus Hymenoscyphus
ericae (Read) Korf & Kernan in pure culture and V. macrocarpon in the mycorrhizal (M) or non‐mycorrhizal (NM) condition as test organisms. The experiments were designed to test the hypothesis that the N contained in these substrates can be mobilized by the mycorrhizal endophyte. The ability of the endophyte to utilize the substrates was determined by measuring fungal yields and by assessing the presence of its extra‐cellular protease and chitinase enzymes. Transfer of N to the host by the endophyte was determined through measurements of plant yield and
tissue N contents. H. ericae produced a significantly greater yield on shoot and mycorrhizal root necromass than on non‐mycorrhizal root necromass. The extra‐cellular enzymes protease and chitinase were produced by the fungus when grown on the M root necromass. The fungus also transferred N to the host plant, up to 76% of N contained in the substrate being found in M plants whereas less than 5% was present in their NM counterparts.
Molecular markers for the identification of the ectomycorrhizal fungus Tuber borchii
Authors: BERTINI L. , AGOSTINI D. , POTENZA L. , ROSSI I. , ZEPPA S. , ZAMBONELLI A. , STOCCHI V.
Published: March 2003

Five species of white truffle were classified using PCR‐based techniques. RAPD (random amplified polymorphic DNA) fingerprints and specific pairs of primers were used. A RAPD fragment was constant in Tuber borchii Vittad. isolates and polymorphic among the other species. Two molecular markers specific for T. borchii were developed from the sequence of the non‐polymorphic RAPD fragment and from regions flanking the 5′‐3′ ends of a truffle gene. These markers were applied in the identification of T. borchii fruit bodies, mycelia and mycorrhizas, allowing us to monitor the development of this fungus during its entire life cycle.
Localization of calcium ions in wounded characean internodal cells
Authors: FOISSNER ILSE
Published: March 2003

Ca2+ was localized in chemically injured internodal cells of the characean alga Nitella flexilis (L.) Ag. using alizarin red and antimonate precipitation. The presence of Ca2+ in the antimonate precipitates was verified by X‐ray analysis and EGTA chelation. Callose‐containing amorphous wound walls were induced by 0·1 mm chlortetracycline (CTC) and cellulosic fibrillar wound walls were induced by 50 mm CaCl2. Numerous precipitates were found in the amorphous wound walls and in the adjacent cytoplasm. Precipitates were mainly localized in single membrane‐bound cisternae, probably of the endoplasmic reticulum, which accumulate at the wound and become a component of the amorphous wound wall via membrane fusion. In fibrillar wound walls, which do not contain membranous residues, precipitate density was significantly lower and similar to that in the secondary cell wall.

The data suggest that the high Ca2+ content of amorphous wound walls is due to incorporation of cytoplasmic Ca2+ stores. The possible function of amorphous wound walls in maintaining cellular Ca2+ homeostasis is discussed.
Tansley Review No. 95: 15N natural abundance in soil–plant systems
Authors: Högberg Peter
Published: March 2003

The following citations were erroneously omitted from the ‘References’:

Groffman PM, Zak DR, Christensen S, Mosier A, Tiedje JM. 1993. Early spring nitrogen dynamics in a temperate forest landscape. Ecology74: 1579–1585.

Handley LL, Brendel O, Scrimgeour CM, Schmidt S, Raven JA, Turnbull MH, Stewart GR. 1996. The 15N natural abundance patterns of field‐collected fungi from three kinds of ecosystems. Rapid Communications in Mass Spectrometry10: 974–978.

Handley LL, Daft MJ, Wilson J, Scrimgeour CM, Ingleby K, Sattar, MA. 1993. Effects of the ecto‐ and VA‐mycorrhizal fungi Hydnagium carneum and Glomus clarum on the δ15N and δ13C values of Eucalyptus globulus and Ricinus communis. Plant, Cell and Environment16: 375–382.

Handley LL, Odee D, Scrimgeour CM. 1994.δ15N and δ13C patterns in savanna vegetation: dependence on water availability and disturbance. Functional Ecology8: 306–314.

Handley LL, Raven JH. 1992. The use of natural abundance of nitrogen isotopes in plant physiology and ecology: commissioned review. Plant, Cell and Environment15: 965–985.

Handley LL, Scrimgeour CM. 1997. Terrestrial plant ecology and 15N natural abundance: the present limits to interpretation for uncultivated systems with original data from a Scottish old field. Advances in Ecological Research27: 133–212.

Hansen AP, Pate JS. 1987. Evaluation of the 15N natural abundance method and xylem sap analysis for assessing N2 fixation of understorey legumes in jarrah (Eucalyptus marginata Donn ex Sm.) forest in S.W. Australia. Journal of Experimental Botany38: 1446–1458.

New Phytologist apologizes unreservedly to all authors of the above papers for this error.
Adaptations for an amphibious life: changes in leaf morphology, growth rate, carbon and nitrogen investment, and reproduction during adjustment to emersion by the freshwater macrophyte Littorella uniflora
Authors: ROBE W. E. , GRIFFITHS H.
Published: March 2003

Littorella uniflora (L.) Ascherson is a small, perennial, amphibious rhizophyte of rosette life‐form which is common along the margins of lakes, tarns and reservoirs where water‐level fluctuations are often rapid and unpredictable. The majority of plants are continuously submersed and reproduce vegetatively, but a small proportion become completely emersed for variable lengths of time, when flowering and seed set occur. To find out how L. uniflora adjusts to sudden emersion we studied the plants at a reservoir where water level falls each spring and remains low throughout the summer; L. uniflora adjusted very quickly showing a degree of phenotypic plasticity not expected in a ‘stress tolerator’, including the production of a new set of terrestrial leaves with reduced lacunal volume and increased stomatal density, a rapid increase in leaf growth rate, and flowering within 3–4 wk. Comparison of terrestrial L. uniflora with aquatic plants growing permanently submersed in lake and tarn habitats showed that three to fourfold more carbon (C) and nitrogen (N) was incorporated into above‐ground biomass by emersed plants. However, ramet production in the aquatic environment appeared to be more costly, in terms of C and N invested, than terrestrial flower and seed production. The combination of continuous, submersed vegetative spread with the capacity for a high degree of phenotypic plasticity allowing some flower and seed production to occur during brief periods of emersion seems to account for the success of this plant in the amphibious niche.
Foliar application of nitrate or ammonium as sole nitrogen supply in Ricinus communis. II. The flows of cations, chloride and abscisic acid
Authors: PEUKE ANDREAS D. , JESCHKE W. DIETER , HARTUNG WOLFRAM
Published: March 2003

Following a precultivation with pedospheric nitrogen nutrition, Ricinus plants were supplied with nitrogen solely by spraying nitrate or ammonium solution onto the leaves during the experimental period. The chemical composition of tissues, xylem and phloem exudates was determined and on the basis of the previously determined nitrogen flows (Peuke et al., New Phytologist (1998), 138, 657–687) the flows of potassium, sodium, magnesium, calcium, chloride and ABA were modelled. These data, which permit quantification of net‐uptake, transport in xylem and phloem, and utilization in shoot and root, were compared with results obtained in plants with pedospherically‐supplied nitrate or ammonium and data in the literature. Although the overall effects on the chemical composition of supplying ammonium to the leaves were not as pronounced as in pedospherically supplied plants, there were some typical responses of plants fed with ammonium (ammonium syndrome). In particular, in ammonium‐sprayed plants uptake and transport of magnesium decreased and chloride uptake was increased compared with nitrate‐sprayed plants. Furthermore, acropetal ABA transport in the xylem in ammonium‐sprayed Ricinus was threefold higher than in nitrate‐sprayed plants. Additionally, concentrations of anions were more or less increased in tissues, particularly in the roots, and transport fluids. The overall signal from ammonium‐sprayed leaves without a direct effect of ammonium ions on uptake and transport systems in the root is discussed.
Can an increased copper requirement in copper‐tolerant Mimulus guttatus explain the cost of tolerance? II. Reproductive phase
Authors: HARPER FRANCES A. , SMITH SUZANNE E. , MACNAIR MARK R.
Published: March 2003

Circumstantial evidence suggests that plants that have evolved metal tolerance are at a disadvantage on normal soil, i.e. there is a cost of tolerance. One hypothesis for the cause of this cost is that individuals have a greater requirement for copper, and so suffer micronutrient deficiency on normal soils, as a result of a reduced uptake, distribution and/or utilization of copper. We provided highly and less copper‐tolerant plants of Mimulus guttatus Fischer ex DC. (the common monkey flower) with sub‐optimal copper, and demonstrated the importance of copper as an essential micronutrient during the reproductive phase, both in the production of viable pollen and in seed set. We also looked at the effect of sub‐optimal copper supply on the growth of the microgametophyte, and the efficiency with which seed was set. No evidence was found that highly tolerant plants have an increased copper requirement during the reproductive phase. This is in agreement with earlier work on Mimulus guttatus, which investigated the copper requirement of highly tolerant plants during vegetative growth and found that any differences in copper requirement were small. The ‘metal requirement hypothesis’ is, therefore, not the sole explanation for the cost of copper tolerance in M. guttatus.
The arbuscular mycorrhizal fungi of Hyacinthoides non‐scripta II. Seasonal and spatial patterns of fungal populations
Authors: MERRYWEATHER JAMES , FITTER ALASTAIR
Published: March 2003

Roots of bluebell (Hyacinthoides non‐scripta (L.) Chouard ex Rothm.) are colonized by a range of fungal symbionts from several genera of the order Glomales. Using the identification scheme described in Merryweather & Fitter (1998), arbuscular mycorrhizal (AM) fungi in bluebell roots were quantified throughout the single growing season of 1994–5 and compared with populations of spores found in the soil around the roots.

In the early part of the growing season, when its activity is entirely subterranean (autumn and winter), bluebell habitually associates with a Scutellospora morphotype which is almost certainly S. dipurpurescens Morton & Koske (emend. Walker, 1993) whose spores occur in the root zone. This is the time of maximum phosphorus inflow and bulb‐stored carbohydrate utilization by this mycorrhiza. A diverse flora of other AM fungal morphotypes (Acaulospora and Glomus), which might also form mycorrhizas with other plants in the vicinity of bluebells, invade the roots later in the season (spring), when P inflow is reduced and carbohydrate is available as fresh photosynthate. Their contribution to the mycorrhiza might be less than that of Scutellospora, particularly in terms of P assimilation.

Both AM fungi in roots and glomalean spores recovered from soil around bluebell roots showed a significant degree of correlation with the vegetation within which the test plants grew. In the case of AM fungi in roots, Scutellospora showed no special preference for either, but Glomus correlated with a canopy of sycamore (Acer pseudoplatanus L.) and Acaulospora with oak (Quercus petraea (Mattuschka) Liebl.). Spores which most closely resembled S. dipurpurescens and Acaulospora gerdemannii Schenck & Nicolson were significantly more numerous under sycamore, but a spore like Acaulospora koskei Blaskowski, the most numerous and frequently encountered glomalean spore in the system, showed no preference for areas dominated by either tree. There was no significant relationship between AM fungal populations in bluebell roots and glomalean spores recovered from associated soil.

The two spore taxa most frequently found in the vicinity of bluebell roots (A. koskei and S. dipurpurescens) were also found in lower numbers in soil from a region of the field site in which bluebell was absent, indicating that the main bluebell AM fungi do not exclusively associate with that host.
Interactive effects of elevated [CO2] and drought on cherry (Prunus avium) seedlings I. Growth, whole‐plant water use efficiency and water loss
Authors: CENTRITTO MAURO , LEE HELEN S. J. , JARVIS PAUL G.
Published: March 2003

Seeds of cherry (Prunus avium) were germinated and grown for two growing seasons in ambient (∼350 μmol mol−1) or elevated (ambient+∼350 μmol mol−1) CO2 mole fractions in six open‐top chambers. The seedlings were fertilized once a week, following Ingestad principles in order to supply mineral nutrients at free‐access rates. In the first growing season gradual drought was imposed on rapidly growing cherry seedlings by withholding water for a 6‐wk drying cycle. In the second growing season, the rapid onset of drought was imposed at the height of the growing season on the seedlings which had already experienced drought in the first growing season. Elevated
[CO2] significantly increased total dry‐mass production in both water regimes, but did not ameliorate the growth response to drought of the cherry seedlings subjected to two sequential drying cycles. Water loss did not differ in either well watered or droughted seedlings between elevated and ambient [CO2]; consequently whole‐plant water‐
use efficiency (the ratio of total dry mass produced to total water consumption) was significantly increased. Similar patterns of carbon allocation between shoot and root were found in elevated and ambient [CO2] when the seedlings were the same size. Thus, elevated [CO2] did not improve drought tolerance, but it accelerated ontogenetic development irrespective of water status.
Spatial distribution of discrete RAPD phenotypes of a root endophytic fungus, Phialocephala fortinii, at a primary successional site on a glacier forefront
Authors: JUMPPONEN ARI
Published: March 2003

Phialocephala fortinii is among the few identified hyphomycetes belonging to the Mycelium radicis atrovirens complex. This ‘dark‐septate endophyte’ has a global distribution and colonizes a wide variety of host plants. In this study, the spatial distribution of discrete genets of P. fortinii on the forefront of a receding glacier was analysed using the randomly amplified polymorphic DNA (RAPD) technique to determine plants colonized and patterns of colonization. In two consecutive years of sampling, a total of 74 isolates of P. fortinii were obtained from nine plant species, typically ectomycorrhizal, ericoid mycorrhizal or non‐mycorrhizal. The isolates showed substantial variation, sharing on average approx. half the RAPD markers. In the first year, three isolates belonging to a single genet were obtained from two plants separated by a distance of nearly 1.5 m. The continuity of this genet was assessed by a sampling the following year. No isolates similar to that, or any of the genets collected the year before were observed. Consequently, the identical isolates from the previous year were concluded to represent discontinuous ramets. Two additional large genets were observed during the second year of sampling, which inhabited roots of several plants representing three different species. These data suggest that the sharing of P. fortinii genets among plant species might play a fundamental role in adaptation and interaction within the whole plant community in a system undergoing primary succession.
The host range of Plasmodiophora brassicae and its relationship to endogenous glucosinolate content
Authors: LUDWIG‐MÜLLER J. , BENNETT R. N. , KIDDLE G. , IHMIG S. , RUPPEL M. , HILGENBERG W.
Published: March 2003

The host range of the soilborne obligate biotroph, Plasmodiophora brassicae was investigated. Evidence is presented that infection by P. brassicae might occur in non‐Brassica species, leading to the potential formation of resting spores. Structures resembling P. brassicae were found in the root cortex of Tropaeolum majus, Carica papaya, Reseda alba and Beta vulgaris as demonstrated by scanning electron microscopy. Inoculation of Brassica rapa roots with spores extracted from either T. majus or B. vulgaris roots which had been previously inoculated with P. brassicae led to development of clubroot in the roots of B. rapa. It was also shown that the development of the symptom might be correlated with glucosinolate content, although other host factors are implicated in the B. vulgaris interaction with P. brassicae. In the glucosinolate‐containing non‐Brassicas, T. majus and C. papaya, the concentrations of benzylglucosinolate increased markedly in roots inoculated with P. brassicae, compared with the controls. There were also increases in concentrations of benzylglucosinolate in leaves of T. majus after P. brassicae infection. However, in R. alba roots, the total glucosinolate content decreased after inoculation with P. brassicae compared with the controls. High root concentrations of 2‐OH‐2‐phenylethylglucosinolate (glucobarbarin) compared with low root indole glucosinolates in this species might limit P. brassicae infection and development. The importance of our investigations in relation to cultivation of non‐Brassica species on fields infested with P. brassicae is discussed.
Characterization and genetic mapping of a mutation (ms35) which prevents anther dehiscence in Arabidopsis thaliana by affecting secondary wall thickening in the endothecium
Authors: DAWSON J. , SÖZEN E. , VIZIR I. , VAN WAEYENBERGE S. , WILSON Z. A. , MULLIGAN B. J.
Published: March 2003

The male sterile mutant, ms35, of Arabidopsis thaliana was produced by X‐irradiation of seeds. The mutant
produces fertile pollen, but is male sterile because the anthers do not dehisce. Anther development in ms35 plants occurs as in wild‐type Arabidopsis until shortly after microspores are released from meiotic tetrads. Thereafter, in the wild type, bands of lignified, cellulosic secondary wall thickenings are laid down around the cells of the anther endothecium. In contrast, wall thickenings are not formed in the endothecium of the ms35 mutant. Development of other lignified tissues, for example the vascular tissue of the stamen, occurs normally in ms35 plants. In mutant anthers, as pollen maturation is completed, the stomium is cleaved but the anther wall does not retract to release pollen. The block in anther dehiscence in ms35 plants is specifically correlated with the absence of endothecial wall thickenings. The ms35 mutation represents the first genetic evidence in support of the proposed role of the endothecium in anther dehiscence. The ms35 gene was mapped to the top arm of chromosome 3 (hy2‐(4.17±2.31 cM)‐ms35‐(32.14±5.45 cM)‐gl1).
A mechanistic model of photoinhibition
Authors: MARSHALL HELEN L. , GEIDER RICHARD J. , FLYNN KEVIN J.
Published: March 2003

A mechanistic model was developed, to simulate the main facets of photoinhibition in phytoplankton. Photoinhibition is modelled as a time dependent decrease in the initial slope of a photosynthesis versus irradiance curve, related to D1 (photosystem II reaction centre protein) damage and non‐photochemical quenching. The photoinhibition model was incorporated into an existing ammonium‐nitrate nutrition interaction model capable of simulating photoacclimation and aspects of nitrogen uptake and utilization. Hence the current model can simulate the effects of irradiance on photosynthesis from sub‐saturating to inhibitory photon flux densities, during growth on different nitrogen sources and under nutrient stress. Model output conforms well to experimental data, allowing the extent of photoinhibition to be predicted under a range of nutrient and light regimes. The ability of the model to recreate the afternoon depression of photosynthesis and the enhancement of photosynthesis during fluctuating light suggests that these two processes are related to photoinhibition. The model may be used to predict changes in biomass and/or carbon fixation under a wide range of oceanographic situations, and it may also help to explain the progression to dominance of certain algal species, and bloom formation under defined irradiance and nutrient conditions.
Does resource availability modulate shade avoidance responses to the ratio of red to far‐red irradiation? An assessment of radiation quantity and soil volume
Authors: MONACO THOMAS A. , BRISKE DAVID D.
Published: March 2003

We conducted two experiments to investigate the expression of shade avoidance in response to low ratios of red to far‐red irradiation (R∶FR) in the C4 perennial grass Schizachyrium scoparium at two levels of above‐ground (photosynthetic photon flux density (PFD) 400–700 nm) and below‐ground (soil volume) resource availability and in plants of two ages. Young plants showed greater sheath and ramet height in response to low R∶FR and old plants showed reduced ramet initiation in experiments one and two, respectively, but both responses were not expressed simultaneously in either group. Growth of all ramet variables, including ramet initiation, was suppressed in small as opposed to large soil volumes. By contrast, architectural variables, but not ramet initiation, were greater for plants grown in low as opposed to ambient PFD. However, expression of shade avoidance to low R∶FR was not significantly affected by either level of PFD or soil volume. We must conclude that the levels of resource availability provided do not modulate shade avoidance in this perennial grass. These results demonstrate that S. scoparium is capable of expressing shade avoidance in response to low R∶FR, but inconsistent juvenile ramet initiation and architectural responses in plants of different ages and phenological stages of development indicate that the shade avoidance response might not be expressed consistently throughout the life of plants.
Assessing root death and root system dynamics in a study of grape canopy pruning
Authors: COMAS LOUISE H. , EISSENSTAT DAVID M. , LAKSO ALAN N.
Published: March 2003

Defining root death in studies of root dynamics is problematic because cell death occurs gradually and the resulting effects on root function are not well understood. In this study, metabolic activity of grape roots of different ages was assessed by excised root respiration and tetrazolium chloride reduction. We investigated changes in metabolic activity and patterns of cell death occurring with root age and changes in root pigmentation. Tetrazolium chloride reduction of roots of different ages was strongly correlated to respiration (R2 = 0.786). As roots aged, respiration
and tetrazolium chloride reduction declined similarly, with minimum metabolic activity reached at six weeks.
Tetrazolium chloride reduction indicated that the onset of root browning corresponded to a 77% reduction in
metabolic activity (P < 0.001). Anatomical examination of roots at each pigmentation stage showed that even
though some cells in brown roots were still alive, these roots were functionally dead. The effect of using different
definitions of root death in relation to root survivorship was determined in a study of ‘Concord’ grapes with two
pruning treatments, using three criteria for root death: browning, blackening or shriveling, and disappearance.
There was no effect of vine pruning on root life span when life span was defined as the time from first appearance
to the onset of browning. However, if death was judged as the point when roots either became black or shriveled
or disappeared, vine pruning decreased root life span by 34% and 40%, respectively (P < 0.001), and also increased
the decay constant for root decomposition by about 45% (P < 0.001). We conclude that the discrepancy among determinations of root life span assessed with different definitions of death might be partly caused by the latter evaluations of root life span incorporating a portion of root decomposition in definitions of root death.
Tansley Review No. 114
Authors: CRAWFORD R. M. M.
Published: March 2003

A cyclic behaviour in the intensity of maritime conditions which varies with the periodic behaviour of the North Atlantic oscillation has recently become apparent in the climatic record of northern Europe. Periodic increases in oceanicity are usually viewed as having a positive effect on plant survival, as milder winters, reduction of temperature extremes, low risk of exposure to frost, and freedom from drought reduce many aspects of environmental stress. However, warmer winters in maritime environments may also have a powerful influence in creating habitats that are unfavourable for many species. The dangers of long periods of soil saturation for overwintering plants, soaking injury to germinating seeds, premature bud burst in spring, depression of treelines by increased cloud cover and high lapse rates, as well as the constant leaching of soils, are all negative aspects of the maritime environment. Woody species in which root dormancy is delayed by mild winters are particularly vulnerable to the consequences of winter flooding. Subsequent re‐exposure to oxygen as water tables fall in spring can aggravate flooding damage through post‐anoxic injury, leading to severe dieback of anchoring roots. Soil leaching, particularly after human disturbance, can induce nutrient deficiencies and the establishment of oligotrophic communities with reduced productivity. Podzolization and iron pan formation have in the past facilitated the processes of paludification in oceanic regions. The resulting spread of bogs and acid moorlands can further reduce the potential for productivity in both agriculture and natural plant communities. Given the probability that current climatic trends may increase the degree of oceanicity in western and northern regions of Europe, the potentially negative consequences of such a climatic change need to be considered in relation to future ecological changes and their consequences for conservation and land use.

contents

Summary
257

I.
defining and quantifying oceanicity
257

II.
ecological consequences of oceanicity
261

III.
ecological history of oceanicity in western europe
263

IV.
positive and negative influences of oceanicity
267

V.
modifying effects of oceanicity on plant distribution
269

VI.
physiological impact of warm winters
271

VII.
treelines and oceanicity
276

VIII.
conclusions
278

Acknowledgements
279

References
279
Nitrogen fertilization reduces Sphagnum production in bog communities
Authors: GUNNARSSON U. , RYDIN H.
Published: March 2003

The effects of increased nitrogen influx on Sphagnum growth and on interspecific competition between Sphagnum
species were studied in a 3‐yr experiment in mires situated in two areas with different rates of airborne N
deposition. Sphagnum growth was recorded after various supplementary N influxes (0, 1, 3, 5 and 10 g m −2 yr−1)
in hummocks and lawn communities. Sphagnum biomass production decreased with increasing N influx in both
areas. After the first season at the low‐deposition site, Sphagnum showed an increased growth in length with the
intermediate N treatment, but in the second and third seasons the control treatment had the highest growth in
length. Capitulum dry mass increased with increasing N influx. Sphagnum N concentration and N/P quotient
were higher at the high‐ than at the low‐deposition site. The low quotient at the low‐deposition site, together with
the initial growth increase with intermediate N supplements, indicates that growth was N‐limited at this site, but
our lowest N supplement was sufficient to reduce growth. The N treatments had no effect on interspecific
competition between the Sphagnum species. This indicates that the species have similar responses to N. The
species studied all occur naturally on ombrotrophic, N‐poor sites and show low tolerances to increased N influx.
Reduced Sphagnum production may affect the carbon balance, changing the mires from C sinks to sources.
Uptake of glycine by field grown wheat
Authors: Näsholm Torgny , Huss‐Danell Kerstin , Högberg Peter
Published: March 2003

Uptake of glycine, a simple organic nitrogen (N) source, directly from the soil is shown here in a conventionally cropped wheat ( Triticum aestivum ) field.

Wheat plants were harvested after tracer injections into the soil of two forms of dual‐labelled amino acid; [ 13C2], [15N]‐glycine and 2‐[13C], [15N]‐glycine. Uptake of intact amino acid was analysed by stable isotope–, and gas chromatography–, mass spectrometry.

Significant increases in 13
C were found in root extracts for all glycine‐treated plants. Regression analysis of excess
13
C vs excess
15 N for the two glycine forms showed that at least 20% of absorbed glycine‐N was derived from uptake of intact glycine. Gas chromatography–mass spectrometry was used to verify the presence of intact dual‐labelled glycine in wheat roots. Results also indicated that glycine decarboxylase had a minor role in metabolism of absorbed glycine in wheat roots. Microbial metabolism in the soil did, however, result in rapid decarboxylation of added glycine.

Field‐grown wheat takes up glycine directly from the soil; the dependence of agricultural plants on nitrate and ammonium as the only forms of available N is therefore questionable.
Seedling performance of pasture species under elevated CO2
Authors: Edwards G. R. , Newton P. C. D. , Tilbrook J. C. , Clark H.
Published: March 2003

The effects of elevated CO2 on seedling recruitment are presented for the pasture species Anthoxanthum odoratum, Cerastium glomeratum, Leontodon saxatilis, Lolium perenne, Poa pratensis and Trifolium repens.

 Seeds collected from pastures maintained at ambient (360 µl l−1) and elevated (475 µl l−1) CO2 were measured for germination and seedling growth in a reciprocal design under ambient and elevated CO2.

 Seedlings of A. odoratum and L. perenne from elevated‐CO2‐developed seeds were heavier than those from ambient‐CO2‐developed seeds but only when the seedlings were grown at elevated CO2. Elevated‐CO2‐developed seeds had higher germination and seedling mass in T. repens and lower germination and seedling mass in L. saxatilis, irrespective of the CO2 concentration after sowing. There were more L. saxatilis and T. repens seedlings in pastures maintained at elevated than ambient CO2; a seed addition experiment showed that this was due mainly to the increased seed production of these species under elevated CO2. Seedling recruitment of C. glomeratum and P. pratensis was unaffected by elevated CO2.

 Species exhibited variable responses to seed development under elevated CO2 that could potentially alter community composition by influencing seedling recruitment.