bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of ambient ozone concentrations on contents of non‐structural carbohydrates in young Picea abies and Fagus sylvatica
Authors: LUX D. , LEONARDI S. , MÜLLER J. , WIEMKEN A. , FLÜCKIGER W. 
Published: March 2003

summaryYoung spruce (Pirea abies [L.] Karst; 2‐yr) and beech trees (Fagus sylvatica L.; current‐year and 1‐yr‐old seedlings) were grown under field conditions at a rural site near the city of Base] (Schonenbuch; 400 m above sea level) and 2‐yr‐old spruce trees at an elevated montainous site (Wengernalp; 1890 m above sea level). The plants were exposed in open‐top‐chambers (OTC) either to charcoal‐filtered air or ambient air with ozone being the predominant air pollutant at both sites. The exposures lasted up to 1 yr. At the end of the growth period the plants were harvested and the pool sizes of the major non‐structural carbohydrates were determined. Exposure to ambient air compared with filtered air controls caused an increase of glucose, fructose, pinitol, starch and, in some cases, sucrose in needles whereas carbohydrate contents in roots and twigs of spruce were reduced, in particular at Wengernalp. In beech saplings at Schönenbuch, a significant rise of sucrose and, in some cases, of raffinose, together with a significant reduction of glucose and fructose was observed in buds, leaves, twigs, and roots in ambient air compared with filtered air. In phloem exudates of current year beech seedlings, a 54–160 higher content of carhohydrates was found in ambient air than in filtered air. In roots of the beech saplings, the amount of soluble carbohydrates increased and starch contents mostly decreased. In general, starch storage in roots and stems was more abundant in beech trees. Spruce, especially at the mountainous site, accumulated high amounts of soluble carbohydrates in needles, in particular glucose.
Growth and survival of Azolla filiculoides in Britain. II. Sexual reproduction
Authors: JANES RACHEL 
Published: March 2003

Sporulation in the floating fern Azolla filiculoides Lam. is both frequent and widespread in Britain and might therefore play a greater part in the population dynamics of the species than
has been suggested by earlier reports. In laboratory experiments, increasing plant density and/or phosphorus supply resulted in increased sporulation. It was estimated that a thick mat of 8 kg m2 fresh biomass can produce 380000 microsporocarps and 85000 megasporocarps per m2.Light and temperatures >10°C were necessary for sporocarp germination. Sporocarps could survive exposure to both low temperatures (5°C for at least 3 months) and sub‐zero temperatures (−10°C for at least 18 d). Sporocarps were found to survive storage in water for 3 yr and to germinate from mud samples collected in the field. In laboratory culture, sporeling growth and survival were optimal at 15°C.There is some evidence that A. filiculoides might have adapted to the British climate since its introduction.
Carbon dioxide‐concentrating mechanism and the development of extracellular carbonic anhydrase in the marine picoeukaryote Micromonas pusilla
Authors: IGLESIAS‐RODRÍGUEZ M. D. , NIMER N. A. , MERRETT M. J. 
Published: March 2003

A range of marine photosynthetic picoeukaryote phytoplankton species grown in culture were screened for the presence of extracellular carbonic anhydrase (CAext), a key enzyme in inorganic carbon acquisition under carbon‐
limiting conditions in some larger marine phytoplankton species. Of the species tested, extracellular carbonic anhydrase was detected only in Micromonas pusilla Butcher. The rapid, light‐dependent development of CAext when cells were transferred from carbon‐replete to carbon‐limiting conditions was regulated by the available free‐
CO2 concentration and not by total dissolved inorganic carbon. Kinetic studies provided support for a CO2‐
concentrating mechanism in that the K0.5[CO2] (i.e. the CO2 concentration required for the half‐maximal rate of photosynthesis) was substantially lower than the Km[CO2] of Rubisco from related taxa, whilst the intracellular carbon pool was at least seven fold greater than the extracellular DIC concentration, for extracellular DIC values ⩽1.0 mm.It is proposed that when the flux of CO2 into the cell is insufficient to support the photosynthetic rate at an optimum photon irradiance, the development of CAext increases the availability of CO2 at the plasma membrane. This ensures rapid acclimation to environmental change and provides an explanation for the central role of M. pusilla as a carbon sink in oligotrophic environments.
Response of photosynthesis of Sphagnum species from contrasting microhabitats to tissue water content and repeated desiccation
Authors: SCHIPPERGES B. , RYDIN H. 
Published: March 2003

The response of photosynthetic CO2 exchange to tissue water content in five spp. of Sphagnum from contrasting microhabitats (S. fuscum (Schimp.) Klinggr., S. papillosum H. Lindb., S. magellanicum Brid., S. balticum (Russ.) C. Jens. and S. cuspidatum Ehrh. ex Hoffm.) was measured in the laboratory using an infrared gas analyser technique. Experiments were designed to test recovery of net photosynthesis after periodic and long lasting desiccation.The contact between capitula and basal parts of the mosses seems to be important for survival. Isolated capitula cut off from any contact with the water table were not able to recover after complete desiccation (at 15°C for 2–4 d). When contact with the water table is lost, e.g. during long periods of desiccation, recovery of net photosynthesis can take place but only if the water content of the capitula does not fall too far below c. 10–20% of the water content at compensation point.There was no relationship between the ability of net photosynthesis to recover from desiccation and the wetness of the natural microhabitat. Sphagna survive dry periods by avoidance of drying out by high capillarity or dense growth form (as in S. fuscum).
Ecto‐ or arbuscular mycorrhizas – which are best?
Authors: Lodge D. J. 
Published: March 2003

Few topics in ecology are as intriguing or bedeviling as comparative studies of different types of mycorrhizas formed in the same plant species. Attempts to determine the relative benefits from each fungal type to the host plant are fraught with difficulties (Jones et al., 1998), and for this
reason plants that form tripartite associations with arbuscular
and ectomycorrhizal fungi make ideal experimental
systems. Just such a tripartite system is explored in a
report in this issue by Chen et al. (pp. 545–556).Why compare mycorrhizas? Although both ecto‐ and arbuscular mycorrhizas are generally known to increase the uptake of nutrients such as phosphorus and nitrogen in infertile soils, their functions and the benefits they provide to their host plants may not be equivalent (Jones et al., 1998). Hence the ecological benefits of the two types of symbiosis are of great interest to plant community ecologists and researchers studying nutrient cycling. Arbuscular mycorrhizas are formed as a symbiosis of plant roots with primitive fungi of the order Glomales (Zygomycetes), while ectomycorrhizas are formed with higher basidiomycetes and a few ascomycetes. Only a few plant genera and species are capable of forming both types of association, sometimes on the same root tip (Fig. 1), but it is these that are so useful in comparative studies.
Tree and forest functioning in response to global warming
Authors: Saxe Henrik , Cannell Melvin G. R. , Johnsen Øystein , Ryan Michael G. , Vourlitis George 
Published: March 2003

SummaryAlthough trees have responded to global warming in the past – to temperatures higher than they are now – the rate of change predicted in the 21st century is likely to be unprecedented. Greenhouse gas emissions could cause a 3–6°C increase in mean land surface temperature at high and temperate latitudes. Despite this, few experiments have isolated the effects of temperature for this scenario on trees and forests. This review focuses on tree and forest responses at boreal and temperate latitudes, ranging from the cellular to the ecosystem level. Adaptation to varying temperatures revolves around the trade‐off between utilizing the full growing season and minimizing frost damage through proper timing of hardening in autumn and dehardening in spring. But the evolutionary change in these traits must be sufficiently rapid to compensate for the temperature changes. Many species have a positive response to increased temperature – but how close are we to the optima? Management is critical for a positive response of forest growth to a warmer climate, and selection of the best species for the new conditions will be of vital importance.ContentsSummary369I.Introduction370II.Photosynthesis and respiration370III.Soil organic matter decomposition and mineralization373IV.Phenology and frost hardiness376V.Whole tree experimental responses to warming380VI.Changes in species distribution at warmer temperatures381VII.Adaptation and evolution383VIII.Ecosystem level responses to warming387Acknowledgements390References390Appendix I.Temperature response functions399
Structure of fructans in roots and leaf tissues of Lolium perenne
Authors: Pavis N. , Chatterton N. J. , Harrison P. A. , Baumgartner S. , Praznik W. , Boucaud J. , Prud’homme M. P. 
Published: March 2003

Summary

An analysis of fructan structures, to increase the understanding of biosynthetic pathways and enzymology of fructan synthesis in root and leaf tissues of Lolium perenne is reported.
Fructan extracted from stubble of L. perenne plants was analyzed by high performance anion exchange chromatography and pulsed amperometric detection (HPAEC‐PAD) using a new desalting technique. Structures of fructan isomers, separated up to DP16 (DP, degree of polymerization), were established by chromatographic elution times or by GC‐MS.
Fructans of DP8 belonged essentially to three series: inulin series, inulin neoseries and the levan neoseries, which is/are different in glucose (terminal or internal) and linked fructose residues. High DP fructans (DP > 8) comprised 75% molecules with an internal glucose residue. They had some branch points although 1 and 6 kestotetraose could not be detected and the β(2–6) linked fructose residues were 70 times more abundant than the β(2–1) linked fructose residues. Roots, sheaths, leaf blades and elongating leaves accumulated similar fructans although amounts of both low and high, and types of low, DP fructans, differed.
It is proposed that fructans in L. perenne are synthesized via four enzymes: 1‐SST (1‐sucrose‐sucrosefructosyl transferase), 1‐FFT (1‐fructan‐fructanfructosyl transferase), 6G‐FT (6‐glucose‐fructosyl transferase) and 6‐FFT (6‐fructan‐fructanfructosyl transferase) or 6‐SFT (6‐sucrose‐fructanfructosyl transferase).
Physiological responses of Catharanthus roseus (periwinkle) to ash yellows phytoplasmal infection
Authors: Tan Puay Yok , Whitlow Thomas 
Published: March 2003

Summary

Photosynthetic responses of periwinkle (Catharanthus roseus) were compared during disease development after infection by two strains of ash yellows (AshY) phytoplasmas that differed in aggressiveness.
Healthy plants were inoculated by grafting with diseased scions. Mature leaves formed before grafting of diseased scion, and leaves formed during disease development were monitored for physiological changes.
Leaves formed before inoculation remained visually and physiologically asymptomatic until normal senescence. However, leaves formed after inoculation had reduced photosynthesis, due to reductions in both the maximum carboxylation rate (Vcmax) and noncyclic electron transport (Jmax). In these leaves, photoinhibition resulted from photoprotective processes rather than photooxidative damage to PSII reaction centres. Stomatal conductance (Gs) was reduced, but this did not increase the stomatal limitation to photosynthesis. Changes in Gs were not correlated with changes in leaf ABA concentration.
Known differences in phytoplasmal aggressiveness were correlated with degrees of inhibition of photosynthesis and occurence of photoinhibition. AshY phytoplasmas appear to cause metabolic perturbations associated with localized accumulation or multiplication of the pathogen in symptomatic leaves.

AbbreviationsA, net photosynthesis rate; Aa, net photosynthesis rate at ambient [CO2]; Amax, net photosynthesis rate at saturated [CO2]; AshY, ash yellows; Ci, intercellular [CO2]; Fo, Fm, Fv, minimal, maximum and variable fluorescence, respectively; F′m, Fs, maximal and steady state fluorescence in light‐adapted state; Fv/Fm, intrinsic efficiency of PSII; Gs, stomatal conductance; Jmax, maximum noncyclic electron transport; Ls, stomatal limitation; ΦPSII, quantum yield of PSII; qNP, nonphotochemical quenching coefficient; RuBP, ribulose‐1,5‐biophosphate; Vcmax, maximum rate of carboxylation of Rubisco; vpd, leaf‐to‐air vapor pressure deficit; WAG, week after grafting.
Cold adaptation in Arctic and Antarctic fungi
Authors: Robinson Clare H. 
Published: March 2003

SummaryGrowth and activity at low temperatures and possible physiological and ecological mechanisms underlying survival of fungi isolated from the cold Arctic and Antarctic are reviewed here. Physiological mechanisms conferring cold tolerance in fungi are complex; they include increases in intracellular trehalose and polyol concentrations and unsaturated membrane lipids as well as secretion of antifreeze proteins and enzymes active at low temperatures. A combination of these mechanisms is necessary for the psychrotroph or psychrophile to function. Ecological mechanisms for survival might include cold avoidance; fungal spores may germinate annually in spring and summer, so avoiding the coldest months. Whether spores survive over winter or are dispersed from elsewhere is unknown. There are also few data on persistence of basidiomycete vs microfungal mycelia and on the relationship between low temperatures and the predominance of sterile mycelia in tundra soils. Acclimation of mycelia is a physiological adaptation to subzero temperatures; however, the extent to which this occurs in the natural environment is unclear. Melanin in dark septate hyphae, which predominate in polar soils, could protect hyphae from extreme temperatures and play a significant role in their persistence from year to year.
Biology of mycorrhizal associations of epacrids (Ericaceae)
Authors: Cairney John W. G. , Ashford Anne E. 
Published: March 2003

SummaryEpacrids, a group of southern hemisphere plants formerly considered members of the separate family Epacridaceae, are in fact most closely allied to the Vaccinioid tribe (Ericaceae). Epacrids and other extant ericoid mycorrhiza‐forming plants appear to have a monophyletic origin. In common with many Ericaceae they form ericoid mycorrhizas. ITS sequence data indicate that the fungi forming ericoid mycorrhizas with epacrids and other extant Ericaceae are broadly similar, belonging to a poorly defined group of ascomycetes with phylogenetic affinities to Helotiales. The basic development and structure of ericoid mycorrhizal infections in epacrids is similar to other Ericaceae. However, data are limited on the structure and physiology of both hair roots and ericoid mycorrhizas for all Ericaceae. Relatively little is known about the functional significance of ericoid mycorrhizas in epacrids in southern hemisphere habitats that are often poor in organic matter accumulation. However the abilities of fungal endophytes of epacrids to utilize organic N and P substrates equal those of endophytes from northern hemisphere heathland plant hosts. Investigations using 15N/13C‐labelled organic N substrates suggest that mycorrhizal endophytes are important, at least, to the N nutrition of their epacrid hosts in some habitats.

Contents

Summary
305

I.
Epacrid plant hosts
306

II.
Evolution of ericoid mycorrhizas in epacrids
306

III.
Epacrid hair roots and their mycorrhizal associations
307

IV.
Seasonality and incidence of mycorrhizal infection
310

V.
Structure and development of mycorrhizal associations
311

VI.
Nature of the mycorrhizal fungal endophytes
315

VII.
Community and population biology of mycorrhizal endophytes
318

VIII.
Functional aspects of mycorrhizas in epacrids
319

IX.
Conclusions
322

Acknowledgements
322

References
322
Biodegradation of linuron in a Phaseolus bioassay detected by chlorophyll fluorescence
Authors: Hulsen Kris , Top Eva M. , Höfte Monica 
Published: March 2003

Summary• Measuring chlorophyll fluorescence of sensitive indicator plants is a promising approach to follow microbial degradation of the photosystem II (PSII) inhibiting herbicide linuron in a plant–microbial bioassay.• Both pulse amplitude modulation (PAM) fluorimetry and a stroboscope‐based Chla fluorescence imaging system were used to monitor the phytotoxic effect of linuron applied to bean (Phaseolus vulgaris) plants.• Inoculation of a hydroponic model system with a linuron‐degrading microbial consortium mostly neutralized the phytotoxic effect of the linuron, applied at 0.1 mg l−1 and 1 mg l−1. This indicated that the inoculum was even able to degrade linuron at substrate concentrations (0.1 mg l−1) that were not detectable by HPLC analysis. The bioprotective effect of the inoculum was also demonstrated when 5 mg l−1 of linuron was spiked into a soil substrate.• This is the first report on the use of chlorophyll fluorescence to demonstrate biodegradation. This method is particularly suited for the detection of low linuron concentrations and could probably also be used for other xenobiotics interfering with photosynthesis.
Cenococcum geophilumpopulations show a high degree of genetic diversity in beech forests
Authors: Jany Jean‐Luc , Garbaye Jean , Martin Francis 
Published: March 2003

Summary• The asexual ectomycorrhizal fungusCenococcum geophilum, known for its wide host and habitat range, has been suggested to provide isolate‐dependant drought protection to fine roots. However, little is known about its genetic structure at the fine scale.• Genetic diversity and population structure ofC. geophilumat the regional and stand scales was surveyed in five beech (Fagus silvatica) forests in northeastern France. The stands were selected for their contrasting climatic and edaphic features to assess the effect of environmental factors on population structure.• The genetic diversity ofC. geophilumwas estimated using RAPD, PCR/RFLP of the rDNA internal transcribed spacer (ITS) and PCR/RFLP and sequencing of an anonymous sequence characterized amplified region (SCAR) on ectomycorrhizas and sclerotia‐derived mycelial cultures.• A high degree of genetic diversity was observed between and within beech stands inC. geophilumpopulations. These results suggest the occurrence of a high rate of mitotic or meiotic recombination and an effect of stand features on population structure.
Biochemical and molecular characterization of NADP‐glutamate dehydrogenase from the ectomycorrhizal fungus Tuber borchii
Authors: Vallorani Luciana , Polidori Emanuela , Sacconi Cinzia , Agostini Deborah , Pierleoni Raffaella , Piccoli Giovanni , Zeppa Sabrina , Stocchi Vilberto 
Published: March 2003

Summary• NADP‐glutamate dehydrogenase (NADP‐GDH) from Tuber borchii was purified and the corresponding gene was cloned in order to elucidate the physiological role of the enzyme in this ectomycorrhizal fungus.• NADP‐GDH was purified using an anion‐exchange column followed by affinity chromatography. The complete gene was cloned from a 30‐d‐old‐mycelium cDNA library and characterized.• T. borchii NADP‐GDH appears to be physically and kinetically similar to those from other fungi and the deduced amino acid sequence of the gdh gene showed a significant similarity to other fungal NADP‐dependent GDHs. Biochemical and Northern blotting analyses carried out with mycelia grown on different nitrogen sources clearly showed that the regulation of T. borchii NADP‐GDH in response to different nitrogen sources was markedly different from the responses of the NADP‐GDHs of other ascomycetes. Northern blotting analyses highlighted that the gdh gene was also expressed in the symbiotic phase.• The biochemical and molecular data suggest that the fungal NADP‐GDH contributes to the primary nitrogen metabolism in the ectomycorrhizal tissues.
Extramatrical ectomycorrhizal mycelium contributes one‐third of microbial biomass and produces, together with associated roots, half the dissolved organic carbon in a forest soil
Authors: Högberg Mona N. , Högberg Peter 
Published: March 2003

Summary• A large‐scale tree‐girdling experiment enabled estimates in the field of the contribution of extramatrical mycelium of ectomycorrhizal (ECM) fungi to soil microbial biomass and by ECM roots and fungi to production of dissolved organic carbon (DOC).• Tree‐girdling was made early (EG) or late (LG) during the summer to terminate the flow of photosynthate to roots and ECM fungi. Determination of microbial C (Cmicr) and microbial N in root‐free organic soil was performed by using the fumigation–extraction technique; extractable DOC was determined on unfumigated soil.• Soil Cmicr was 41% lower on LG than on control plots 1 month after LG, whereas at the same time (that is, 3 months after EG), the Cmicr was 23% lower on EG than on control plots. Extractable DOC was 45% lower on girdled plots than control plots.• Our results, which are of particular interest as they were obtained directly in the field, clearly demonstrate the important contribution by extramatrical ECM mycelium to soil microbial biomass and by ECM roots to the production of DOC, a carbon source for other microbes.
Linking photorespiration, monoterpenes and thermotolerance in Quercus
Authors: Peñuelas Josep , Llusià Joan 
Published: March 2003

Summary

The functions of two important plant processes, photorespiration and monoterpene production remain controversial. Here, we investigated one possible function, that of protection of plants from photodamage at high temperatures.
Fluorescence, reflectance, monoterpene concentrations and visual leaf damage were measured in Quercus ilex
seedlings exposed to temperature increases from 25 to 50°C (in 5°C steps) under photorespiratory (21% O
2
) or nonphotorespiratory (2% O
2 ) atmospheres, and under control or terpene fumigation conditions.
Lower variable to maximum fluorescence ratio (Fv : Fm: potential photochemical efficiency of photosystem II, PSII) and electron transport rate (ETR) were found in nonphotorespiratory conditions at temperatures greater than 35°C. Monoterpene concentrations were also lower, and leaf damage greater, in the low O 2 atmospheres. Monoterpene fumigation, which increased the foliar terpene concentrations by two‐ to four‐fold, increased the photochemical efficiency between 35°C and 50°C, and decreased leaf damage, only under the nonphotorespiratory conditions.
These results provide evidence that: photorespiration decreases photodamage, especially at high temperatures; photorespiration increases monoterpene production; plants are able to acquire exogenous monoterpenes and the acquisition response to temperature follows the stomatal conductance response; and monoterpenes can replace photorespiration in protection from photodamage at high temperatures, possibly by scavenging oxygen‐reactive species, but they do not provide additional thermotolerance.