bluuebunny/crossref_metadata_2025 huggingface dataset:
Carbohydrate oxidases in ericoid and ectomycorrhizal fungi: a possible source of Fenton radicals during the degradation of lignocellulose
Authors: BURKE R. M. , CAIRNEY J. W. G.
Published: March 2003

Isolates of the ericoid mycorrhizal fungus Hymenoscyphus ericae (Read) Korf et Kernan, and the ectomycorrhizal fungi Suillus variegatus (Swartz ex Fr.) and Pisolithus tinctorius (Pers.) Coker & Couch, along with a Cortinarius sp. and the white rot Phanerochaete chrysosporium Burdsall were examined for the ability to oxidize carbohydrates to their corresponding lactones and to excrete the H2O2 produced thereby. All except Phanerochaete chrysosporium were found to express cellobiose oxidase (cellobiose dehydrogenase, EC 1.1.19.88) and glucose oxidase (β‐d‐glucose∶oxygen 1‐oxidoreductase, EC 1.1.3.4) when grown on cellobiose and glucose respectively. Production of extracellular H2O2 was visualized during growth on both substrates using ABTS as the chromogen. According to the Fenton reaction, H2O2 will react with hydrated or chelated Fe(II) in the environment to produce hydroxyl (Fenton) radicals, HO·. Mycelial extracts from each of the mycorrhizal fungi produced HO· in the presence of cellobiose and Fe(II), presumably mediated by H2O2 produced by cellobiose oxidase activity in the extracts. Conditions favourable to HO· production were shown to exist in Modified Melin–Norkrans medium, and the data discussed in relation to previously observed lignin degradation by mycorrhizal fungi.
Thallus initiation and development in the lichen Rhizocarpon lecanorinum
Authors: CLAYDEN STEPHEN R.
Published: March 2003

Ascospore germination, thallus initiation, and areole and prothallus development in the lichen Rhizocarpon lecanorinum Anders were examined using light, fluorescence and scanning electron microscopy. The ascospore germ hyphae remain very short and do not form a prothallus‐like mycelium. Instead, a compact soredium‐like granule develops directly from sporeling contact with a compatible species of Trebouxia. Diffuse initial stages involving non‐trebouxioid algae are lacking. The onset of thallus differentiation is marked by the deposition of rhizocarpic acid in an incipient cortical layer within the apical part of the granule. As pigmentation and cortex‐formation transform this structure into a typical areole, radiating prothallus hyphae are simultaneously initiated from its basal margin. Most areoles formed subsequently in the marginal prothallus lack subtending melanized hyphae and apparently stem from overgrowth by the prothallus of photobiont cells on, or in, the substratum. Apothecia reach maturity in thalli as small as 2 mm in diameter. It is proposed that the lack of diffuse hyphal growth in sporelings and telescoped morphogenesis of R. lecanorinum are part of a life history strategy geared to precocious, heavy investment in ascospore production. The R. lecanorinum–Trebouxia symbiosis has a number of features which make it well‐suited for further studies of the life history and development of prothallus‐forming crustose lichens with sexually reproducing mycobionts.
Seed mass and light‐demand: the need to control for soil–type and plant stature
Authors: GRUBB P. J.
Published: March 2003

Studies on whether or not species which need more light for establishment have smaller seeds should be made between plants of similar mature height living in the same soil and macroclimate. Salisbury's classic comparisons confused differences in light‐requirement during establishment with differences in mature height and in the supply of soil resources.
Seed mass, habitat and life history: a re‐analysis of Salisbury (1942, 1974)
Authors: THOMPSON KEN , HODKINSON DUNMAIL J.
Published: March 2003

A recent re‐analysis of the data of Salisbury (1974) claims his data do not support the hypothesis that seeds of species from shaded habitats are heavier than those from unshaded habitats, partly because the original analysis was inappropriate and partly because of bias in the dataset. We show first that the re‐analysis itself contains errors, and second that the charge of bias is based largely on a misunderstanding. We also show that analysis of a larger dataset, drawn from Salisbury (1942) and from Salisbury (1974), provides convincing support for the hypothesis and suggests that the relationship is independent of life history.
THE THIRD NEW PHYTOLOGIST SYMPOSIUM. Major Biological Issues Resulting from Anthropogenic Disturbance of the Nitrogen Cycle. Lancaster House Hotel, Lancaster University, UK, 3–5 September1997
Authors: Mansfield Terry , Sheppard Lucy , Goulding Keith
Published: March 2003

Presentations and discussions about the impacts of nitrogenous compounds dispersed via the atmosphere, and of ozone as a secondary pollutant
Fructan biosynthesis in Lolium perenne: appraisal of soluble and insoluble enzymatic pathways
Authors: GUERRAND D. , AVICE J. C. , PAVIS N. , PRUD'HOMME M. P. , BOUCAUD J.
Published: March 2003

Previous work on Lolium perenne showed that sucrose∶sucrose fructosyltransferase (SST) activity did not increase concomitantly with fructan synthesis in regrowing leaves or in mature leaf blades of plants that have been subjected to carbohydrate‐accumulating conditions. This was contrary to the pattern of SST activity in roots and stubble. To obtain further insight into the fructan synthesizing activities and to explain this discrepancy, total fructosyltransferase activity (FT) was assayed by increasing the sucrose and the soluble enzyme concentrations and was compared to sedimentable phlein sucrase activity (PS) throughout the regrowth period following defoliation in leaves, stubble and roots. Before analysis on 2‐month‐old plants, PS activity was characterized in dark‐grown coleoptiles, using [U‐14C]sucrose. PS activity had a pH optimum of 6.0 and produced 1‐kestose in addition to high molecular weight fructans with a mean DP of 9. In 2‐month‐old plants, sedimentable PS and FT soluble reactions contained an initial sucrose concentration of 160 mM and 400 mM and proteins equivalent to 1.4 and 2.1 g f. wt of tissue, respectively. In stubble and roots, the FT preparation catalysed the synthesis of large fructans, and the overall pattern resembled the native fructans when separated by anion exchange HPLC. In regrowing leaves, the FT preparation produced low‐DP fructans relatively more than in vivo but synthesized the high‐DP fructan characteristic of the tissue. Moreover, FT activity did not remain at a low level like SST activity but increased from day 5 after defoliation when fructans began to accumulate. PS activity formed very few low‐
DP fructans and 1‐kestose was the main product. Trisaccharides generated by PS activity represented 2–5% of the total trisaccharide synthesis. High‐DP fructans were detectable only when the products of the reaction were concentrated 100 times. Results are discussed with respect to the relative contribution of FT and PS activities for the synthesis of 1‐kestose and fructans in roots, stubble and leaves of Lolium perenne.
Differential responses of UK upland plants to nitrogen deposition
Authors: LEITH IAN D. , HICKS W. KEVIN , FOWLER DAVID , WOODIN SARAH J.
Published: March 2003

Native upland species, Nardus stricta, Eriophorum vaginatum, Erica cinerea and Vaccinium vitis‐idaea were given 3 or 60 kg N ha−1 yr−1, over 2 yr, applied as a mist (NH4NO3). The high N treatment increased above‐ground biomass in all four species, but only significantly in E. cinerea, E. vaginatum and N. stricta. Biomass increases in E. vaginatum and N. stricta resulted from enhanced tiller production rather than shoot elongation. Root growth increased in N. stricta, so that root∶shoot ratio in this species was unchanged by N. Root growth in E. vaginatum, E. cinerea and V. vitis‐idaea did not respond to N and their root∶shoot ratios decreased. Tissue N concentrations increased in both shoots and roots of all species in response to N. The accumulated foliar N did not increase the proportion of N allocated to Rubisco and the photosynthetic capacities of N. stricta, E. vaginatum and V. vitis‐idaea were unchanged. Thus growth responses to N were due to altered allocation rather than increased rate of photosynthesis per unit leaf area. The high N treatment increased flower production significantly in E. cinerea but not in the other species. Although in this experiment dwarf shrubs were more responsive than graminoids to N, in the field at current N inputs the enhanced tillering of the graminoids may be more competitively advantageous, especially where gaps develop in the canopy. Thus increasing N deposition may lead to increased grassiness of upland heath, and in particular, a spread of N. stricta.
Biology of the ectomycorrhizal fungal genus, Rhizopogon
Authors: MASSICOTTE HUGUES B. , MELVILLE LEWIS H. , PETERSON R. LARRY , MOLINA RANDY
Published: March 2003

The morphology and anatomy of ectomycorrhizas of Rhizopogon arctostaphyli, R. ellenae, R. flavofibrillosus, R. occidentalis, R. rubescens, R. smithii, R. subcaerulescens and R. truncatus synthesized on Ponderosa pine (Pinus ponderosa) in glasshouse conditions using spore slurries, are described and compared. All species produced a well‐developed Hartig net, and a well‐developed fungal mantle. The mantles of R. arctostaphyli, R. smithii and R. subcaerulescens ectomycorrhizas were two‐layered with outer mantle hyphae of wider diameter than inner mantle hyphae. The mantle of R. subcaerulescens ectomycorrhizas also had distinctive peg‐like structures (cystidia) along peripheral hyphae. Rhizopogon truncatus ectomycorrhizas were tuberculate in morphology and had a rind‐like mantle enclosing adjacent roots. In addition, several species exhibited crystal inclusions in the outer mantle, presumably at the interface between mantle and soil.
Apical meristems of tomato roots and their modifications induced by arbuscular mycorrhizal and soilborne pathogenic fungi
Authors: FUSCONI A. , GNAVI E. , TROTTA A. , BERTA G.
Published: March 2003

Functional morphological patterns in root apices of tomato (Lycopersicon esculentum) dependent on growth, ageing and infection by the arbuscular mycorrhizal (AM) fungus Glomus mosseae and/or by the soilborne pathogenic fungus Phytophthora nicotianae var parasitica (P. parasitica) were studied. Uninfected root apices were characterized by closed, tri‐layered meristems with nonreticulate nuclei; however, some apices of each treatment lost their meristematic nature, stopped growing and differentiated, becoming ‘parenchymatized’. The pathogenic fungus reduced the apex diameter and the number of mitotically active and viable apices inducing plasmolysis, cell and nucleus degeneration, and necrosis. The AM fungus, on the other hand, produced an increase in apex size and reduced the percentage of necrosis both in uninfected roots and in roots infected by P. parasitica. Thus, the AM fungus protected the apices from the pathogenic infection, allowing normal root growth. Furthermore, larger apices, which produce thicker roots, might indirectly contribute to plant protection. Increased volumes of colonizable tissues favour the spreading of the symbiont, and P. parasitica hyphae are always excluded from arbuscule‐containing cells.
The relationship between leaf composition and morphology at elevated CO2 concentrations
Authors: RODERICK MICHAEL L. , BERRY SANDRA L. , NOBLE IAN R.
Published: March 2003

The composition and morphology of leaves exposed to elevated [CO2] usually change so that the leaf nitrogen (N) per unit dry mass decreases and the leaf dry mass per unit area increases. However, at ambient [CO2], leaves with a high leaf dry mass per unit area usually have low leaf N per unit dry mass. Whether the changes in leaf properties induced by elevated [CO2] follow the same overall pattern as that at ambient [CO2] has not previously been addressed. Here we address this issue by using leaf measurements made at ambient [CO2] to develop an empirical model of the composition and morphology of leaves. Predictions from that model are then compared with a global database of leaf measurements made at ambient [CO2]. Those predictions are also compared with measurements showing the impact of elevated [CO2]. In the empirical model both the leaf dry mass and liquid mass per unit area are positively correlated with leaf thickness, whereas the mass of C per unit dry mass and the mass of N per unit liquid mass are constant. Consequently, both the N∶C ratio and the surface area∶volume ratio of leaves are positively correlated with the liquid content. Predictions from that model were consistent with measurements of leaf properties made at ambient [CO2] from around the world. The changes induced by elevated [CO2] follow the same overall trajectory. It is concluded that elevated [CO2] enhances the rate at which dry matter is accumulated but the overall trajectory of leaf development is conserved.
Factors affecting soil acidification under legumes. III. Acid production by N2‐fixing legumes as influenced by nitrate supply
Authors: TANG C. , UNKOVICH M. J. , BOWDEN J. W.
Published: March 2003

Leaching of nitrate through soil profiles is a major cause of soil acidification. Legume species differ in their ability to take up nitrate (NO3−) and in the degree to which soil NO3− impairs legume nodulation and N2 fixation. This pot experiment examined species variation in N2 fixation and acid production in grain legumes grown for 6 wk on a sandy soil with Ca(NO3)2 added at 0–56.7 mg N kg−1 soil. The eight legumes studied were Lupinus angustifolius (‘Gungurru’), Lupinus albus (‘Kiev mutant’), Lupinus luteus (‘Teo’), Cicer arietinum (Selection T1587), Pisum sativum (‘Dundale’ and ‘Wirrega’), Vicia faba (‘Fiord’) and Lathyrus sativus (Selection 453). While number of nodules was not significantly affected by treatment with NO3−, increasing supply of NO3− decreased nodule mass, with P. sativum‘Wirrega’ being most sensitive and C. arientinum and V. faba least sensitive. The concentrations of nitrogen in plants generally decreased as the supply of NO3− increased. Increasing supply of NO3− decreased the percentage of N2 fixation, most significantly in L. sativus and least in L. albus. In the absence of added NO3−, the amounts of H+ produced per unit biomass (specific acid production) differed by as much as 2.2‐fold among the species, with C. arientinum generating most H+, followed by L. angustifolius, L. luteus, L. albus, V. faba, L. sativus, P. sativum‘Dundale’ and P. sativum‘Wirrega’. This species variation was even greater at higher NO3− supply. In the presence of NO3− at up to 14.2 mg N kg−1, acid production by these legumes correlated well with uptake of excess cations but not with the concentration of nitrogen in plants. For all species, release of H+ declined with increasing supply of NO3−, decreasing most in L. sativus and least in C. arientinum. The results suggest that there might be scope for selecting grain legume species in order to minimize soil acidification by decreasing leaching of NO3−.
Differential responses of grass and a dwarf shrub to long‐term changes in soil microbial biomass C, N and P following factorial addition of NPK fertilizer, fungicide and labile carbon to a heath
Authors: MICHELSEN ANDERS , GRAGLIA ENRICO , SCHMIDT INGER K. , JONASSON SVEN , SLEEP DARREN , QUARMBY CHRIS
Published: March 2003

Microbial immobilization may decrease the inorganic nutrient concentrations of the soil to the extent of affecting plant nutrient uptake and growth. We have hypothesized that graminoids with opportunistic nutrient‐acquisition strategies are strongly influenced by nutrient limitation imposed by microbes, whereas growth forms such as dwarf shrubs are less affected by the mobilization–immobilization cycles in microbes. By adding NPK fertilizer, labile C (sugar) and fungicide (benomyl) over a 5 yr period in a fully factorial design, we aimed to manipulate the sink–source potential for nutrients in a non‐acidic heath tundra soil. After 2 yr, N and P accumulated in the microbial biomass after fertilization with no change in microbial C, which suggests that nutrients did not limit microbial biomass growth. After 5 yr, microbial C was enhanced by 60% in plots with addition of labile C, which points to C‐limitation of the microbial biomass. Microbial biomass N and P tended to increase following addition of labile C, by 10 and 25%, respectively. This caused decreased availability of NH4+ and P, showing close microbial control of nutrient availability. The most common graminoid, Festuca ovina, responded to fertilizer addition with a strong increase, and to labile C addition with a strong decrease in cover, providing the first direct field evidence that nutrient limitation imposed by immobilizing microbes can affect the growth of tundra plants. Also in support of our hypothesis, following addition of labile C the concentrations of N and K in leaves and that of N in roots of F. ovina decreased, whilst the demand of roots for P increased. In contrast, the most common dwarf shrub, Vaccinium uliginosum, was only slightly sensitive to changes in resource availability, showing no cover change after 4 yr addition of labile C and fertilizer, and little change in leaf nutrient concentrations. We suggest that the differential responses of the two growth forms are due to differences in storage and nutrient uptake pathways, with the dwarf shrub having large nutrient storage capacity and access to organic forms of N through its mycorrhizal association. While the fungicide had no effect on ericoid mycorrhizal colonization of roots or symbiotic function inferred from plant 15N natural abundance, it decreased microbial biomass C and N after 2 yr. Throughout the fifth season, the availability of soil NO3− and inorganic P was decreased with no change in microbial biomass C, N or P, suggesting a negative impact of benomyl on N and P mineralization.
Subcellular compartmentation of elements in non‐mycorrhizal and mycorrhizal roots of Pinus sylvestris: an X‐ray microanalytical study. II. The distribution of calcium, potassium and sodium
Authors: BÜCKING HEIKE , HEYSER WOLFGANG
Published: March 2003

The inter‐ and intracellular distribution of the elements calcium, potassium and sodium in non‐mycorrhizal and mycorrhizal roots of Pinus sylvestris dependent on different external nutrient supply conditions was detected by energy‐dispersive X‐ray microanalysis after cryofixation, freeze‐drying and pressure infiltration of the material. In non‐mycorrhizal and mycorrhizal roots, calcium was mainly detectable in the apoplastic regions. The levels in vacuoles and cytoplasm were near the limits of detection by X‐ray microanalysis. Incubation with high concentrations of potassium and sodium, or mycorrhizal infection with Suillus bovinus and Pisolithus tinctorius reduced the amounts of calcium detectable in the roots, especially in the apoplast of cortical cells. The studies revealed that: potassium is mainly localized in cytoplasm and cell walls; the cytoplasmic content is regulated over a wide range of external potassium concentrations; potassium levels in the inner parts of roots are higher than in the outer parts. Mycorrhizal infection with Suillus bovinus had no effect on the inter‐ and intracellular distribution of potassium in roots but, if the external supply was low, the potassium content in shoots was reduced. In non‐mycorrhizal pine roots and those infected with Paxillus involutus an increase in the sodium content of all cell compartments was observed after treatment with high external concentrations of NaH2PO4. However, an increase in sodium content in mycorrhizas of S. bovinus was not detected. The X‐ray microanalytical results are discussed in relation to the apoplastic movement of nutrients in non‐mycorrhizal and mycorrhizal fine roots of pine and to the demand for these nutrients in different intracellular compartments.
Mycorrhiza formation and elevated CO2 both increase the capacity for sucrose synthesis in source leaves of spruce and aspen
Authors: LOEWE ANJA , EINIG WERNER , SHI LANBO , DIZENGREMEL PIERRE , HAMPP RÜDIGER
Published: March 2003

The effects of mycorrhiza formation in combination with elevated CO2 concentrations on carbon metabolism of
Norway spruce (Picea abies) seedlings and aspen (Populus tremula×Populus tremuloides) plantlets were analysed.
Plants were inoculated for 6 wk with the ectomycorrhizal fungi Amanita muscaria and Paxillus involutus (aspen
only) in an axenic Petri‐dish culture at 350 and 700 μl l−1 CO2 partial pressure. After mycorrhiza formation, a
stimulation of net assimilation rate was accompanied by decreased activities of sucrose synthase, an increased
activation state of sucrose‐phosphate synthase, decreased fructose‐2,6‐bisphosphate and starch, and slightly
elevated glucose‐6‐phosphate contents in source leaves of both host species, independent of CO2 concentration.
Exposure to elevated CO2 generally resulted in higher net assimilation rates, increased starch as well as decreased
fructose‐2,6‐bisphosphate (aspen only) content in source leaves of both mycorrhizal and nonmycorrhizal plants.
Our data indicate only slightly improved carbon utilization by mycorrhizal plants at elevated CO2. They demonstrate however, that both factors which modulate the sink‐source properties of plants increase the capacity for sucrose synthesis in source leaves mainly by allosteric enzyme regulation.
The microtubular cytoskeleton during megasporogenesis in the Nun orchid, Phaius tankervilliae
Authors: TUNG S. H. , YE X. L. , ZEE S. Y. , YEUNG E. C.
Published: March 2003

This study examines the microtubular cytoskeleton during megasporogenesis in the Nun orchid, Phaius
tankervilliae. The subepidermal cell located at the terminal end of the nucellar filament differentiates first into an
archesporial cell and then enlarges to become the megasporocyte. The megasporocyte undergoes the first meiotic
division, giving rise to two dyad cells of unequal size. Immunostaining reveals that microtubules become more
abundant as the megasporocyte increases in size. Microtubules congregate around the nucleus forming a distinct
perinuclear array and many microtubules radiate directly from the nuclear envelope. In the megasporocyte,
prominent microtubules are readily detected at the chalazal end of the cell cytoplasm. After meiosis I, the chalazal
dyad cell expands in size at the expense of the micropylar dyad cell. At this stage, new microtubule organizing
centres can be found at the corners of the cells. The appearance of these structures is stage‐specific and they are
not found at any other stages of megasporogenesis. The functional dyad cell undergoes the second meiotic division,
resulting in the formation of two megaspores of unequal size. The chalazal megaspore enlarges and eventually
gives rise to the embryo sac. As the functional megaspore expands, the microtubules again form a distinct
perinuclear array with many microtubules radiating from the nuclear envelope. A defined cortical array of
microtubules has not been found in P. tankervilliae during the course of megasporogenesis.
Ecophysiological differences among Leymus mollis populations across a subarctic dune system caused by environmental, not genetic, factors
Authors: IMBERT ÉRIC , HOULE GILLES
Published: March 2003

Plant species that persist during succession, from the colonization to the stabilization stages, face major environmental changes. Such changes are believed to have significant effects on species performance. In subarctic coastal dune systems, Leymus mollis colonizes the embryo dunes, on the upper limit of the beach. It reaches its
maximum density on the foredune, but also grows on older, stabilized ridges. This paper reports on the phenotypic
variations of some ecophysiological traits associated with the persistence of L. mollis on a dune system on the east
coast of Hudson Bay (northern Quebec). Leymus mollis ramets tend to have a lower net carbon assimilation rate
and water use efficiency, and a higher substomatal CO2 concentration on the stabilized dune than on the foredune. However, these physiological differences cannot be explained by differences in leaf morphology or nitrogen content. Under controlled conditions, ecophysiological differences observed in the field disappear, suggesting that these are not genetic but determined by environmental changes along the foredune‐stabilized dune gradient. We propose that higher net carbon assimilation rate on the foredune might be related to higher sink strength in relation to the growth‐stimulating effect of sand burial.
A lectin from the lichenized Basidiomycete Dictyonema glabratum
Authors: ELIFIO SELENE L. , DE LOURDES C. C. DA SILVA MARIA , IACOMINI MARCELLO , GORIN PHILIP A. J.
Published: March 2003

A lectin with hemagglutinating activity has been isolated from an aqueous extract of the symbiotic phenotype of Dictyonema glabratum and its cyanobacterial photobiont Scytonema sp. The purified lectin had a pI of 6.8 and its
molecular mass was investigated by electrospray ionization mass spectrometry, gel filtration and SDS‐PAGE,
which indicated its native conformation as a dimer formed by two identical subunits of 16540 Da. The lectin is
a glycoprotein with a low degree of glycosylation, containing galactose, xylose, glucose and mannose as neutral
monosaccharides, in addition to glucosamine, which could indicate both N‐ and O‐linkages. Amino acid analysis
showed the predominance of nonpolar residues such as phenylalanine. Agglutination of human erythrocytes
required divalent cations, which is affected by addition of EDTA. The lectin was more stable at 30 °C or less for
at least 1 h and between pH 5.0 and 7.0. Among the various compounds tested for hemagglutination inhibition,
N‐acetylgalactosamine was the most active. The potential role of this lectin in recognition of the compatible cyanobacterial photobiont is discussed.
Comparative study of two spruce species in a polluted mountainous region
Authors: Soukupová J. , Rock B. N. , Albrechtová J.
Published: March 2003

Tolerance to pollution and climatic conditions are compared in Colorado blue spruce ( Picea pungens
) and Norway spruce (
Picea abies ) from two adjacent stands in the Krušné Hory Mountains, Czech Republic.

The anatomy of needles was described quantitatively using image analysis, and the content of photosynthetic pigments, accumulation of lignin and phenolics, and reflective properties of needles of the two species were compared.

Anatomical and morphological adaptations of Colorado blue spruce needles (i.e. lower needle surface area: volume ratio) suggested greater potential resistance to air pollution than Norway spruce. However, no difference in the degree of cell damage was recorded. Although concentrations of chlorophyll, carotenoids and their ratios were similar, lignification and phenolic accumulation was greater in Norway spruce. The red edge inflection point, as well as stress indices and reflectance ratios, suggested an age‐dependent increase in needle damage of both species.

Needles of young Colorado blue spruce and Norway spruce exhibit the same degree of damage in response to air pollutants.
Gender‐specific responses ofPopulus tremuloidesto atmospheric CO2enrichment
Authors: Wang Xianzhong , Curtis Peter S.
Published: March 2003

Dioecious species represent an important component of terrestrial ecosystems, but little is known about gender‐specific responses to elevated atmospheric CO2.

 In an open‐top chamber experiment carried out in Michigan, USA, the physiological and growth responses were studied of male and femalePopulus tremuloidesto elevated CO2 and soil nitrogen concentrations.

 Male trees had a higher net photosynthetic rate than female trees, but the difference was greater at elevated (25%) than at ambient (13%) CO2. Leaf dark respiration, averaged across the growing season, tended to be higher in males than in females, and increased significantly in male and female trees with CO2 enrichment. Female trees had higher total biomass than male trees grown in low‐nitrogen soil and at ambient CO2, but not in other treatments. Elevated CO2 increased the total biomass of males by 58–66% and of females by 22–70%.

 Differing physiological and growth responses to CO2 enrichment by male and female trees should be taken into consideration when predicting the effects of global environmental changes on forest ecosystem structure and functioning.
Evolutionary dynamics of grass genomes
Authors: Gaut Brandon S.
Published: March 2003

The grass family (Poaceae) has been the subject of intense research over the past decade. Although other angiosperm families contain more species and more genera, the Poaceae exceed all other families in ecological dominance and economic importance. Research has focused on the evolutionary relationships among grasses as well as the structure of grass genomes. Here I examine the evolutionary dynamics of grass genomes in a phylogenetic framework. It is clear that grass genomes are evolutionarily labile for many characteristics, including genome size and chromosome number. Variation in genome size among grasses probably reflects fluctuations in the amount of repetitive DNA per genome, but the history and causes of chromosome number changes remain unclear. Despite substantial variation among genomes, comparative maps suggest that grass genomes retain extensive regions of colinearity. By reanalyzing some comparative map data and also by reviewing comparative sequence data, I argue that the current colinearity paradigm requires reassessment.

Contents

Summary
15

I.
Introduction
16

II.
Grass relationships, chromosome numbers and genome size
17

1. Grass relationships
17

2. The timescale of grass evolution
17

3. The evolution of chromosome number
18

4. The evolution of genome size
19

III.
Comparative maps and sequencing
21

1. Comparative maps of the grasses
21

2. Limitations of map data for evolutionary analyses
22

3. Synteny among grass genomes: a reanalysis
23

4. Microsynteny: comparative grass sequences
24

IV.
Conclusions
25

Acknowledgements
26

References
26
Coevolution of roots and mycorrhizas of land plants
Authors: Brundrett Mark C.
Published: March 2003

Here, the coevolution of mycorrhizal fungi and roots is assessed in the light of evidence now available, from palaeobotanical and morphological studies and the analysis of DNA‐based phylogenies. The first bryophyte‐like land plants, in the early Devonian (400 million years ago), had endophytic associations resembling vesicular–arbuscular mycorrhizas (VAM) even before roots evolved. Mycorrhizal evolution would have progressed from endophytic hyphae towards balanced associations where partners were interdependent due to the exchange of limiting energy and nutrient resources. Most mycorrhizas are mutualistic, but in some cases the trend for increasing plant control of fungi culminates in the exploitative mycorrhizas of achlorophyllous, mycoheterotrophic plants. Ectomycorrhizal, ericoid and orchid mycorrhizas, as well as nonmycorrhizal roots, evolved during the period of rapid angiosperm radiation in the Cretaceous. It is hypothesised that roots gradually evolved from rhizomes to provide more suitable habitats for mycorrhizal fungi and provide plants with complex branching and leaves with water and nutrients. Selection pressures have caused the morphological divergence of roots with different types of mycorrizas. Root cortex thickness and exodermis suberization are greatest in obllgately mycorrhizal plants, while nonmycorrhizal plants tend to have fine roots, with more roots hairs and relatively advanced chemical defences. Major coevolutionary trends and the relative success of plants with different root types are discussed.ContentsSummary275I.Introduction276II.Mycorrhizal Fungi276III.The Dawn of Mycorrhizas279IV.Mycorrhizal Associations of Living and Extinct Plants282V.Evolution of Roots288VI.The Root as a Habitat for Fungi290VII.Mycorrhizal Evolution Trends295Acknowledgements298References298
Organic purchasing motivations and attitudes: are they ethical?
Authors: McEachern M.G. , McClean P.
Published: March 2003

Despite the increased documentation of consumers’ purchases of organic food products, the motivations for such purchases are relatively under‐researched. An individual’s choice of food products can be linked clearly to ethical stances, but ethical choices can also vary from individual to individual, from industry to industry and among countries. Consequently, this paper investigates the degree to which ethical beliefs influence Scottish consumer perceptions, beliefs, attitudes and purchasing decisions, with regard to organic dairy products. Consumer purchasing motivations are revealed as being self‐interest‐centred (i.e. better tasting, safer), rather than altruistic. Therefore, to achieve future market development, organic dairy producers cannot rely upon the minority of hardcore green consumers to sustain growth, but must aim to modify perceptions and attitudes of larger consumer segments by implementing educational marketing campaigns that reinforce the ethical, environmental and societal benefits of organic production.
Do consumption expenditures depend on the household’s relative position in the income distribution?
Authors: Abdel‐Ghany Mohamed , Silver J. Lew , Gehlken Amy
Published: March 2003

Even though the permanent income and relative income hypotheses have been introduced in past research to explain consumer behaviour, no previous attempt was undertaken to integrate them in one model. In this article, the hypotheses were synthesized into a single model. The model was empirically tested using data from the 1996 Canadian Family Expenditure Survey. The results indicate that household consumption behaviour is generally explained by both hypotheses when integrated into one model, contrary to previously treating them as mutually exclusive hypotheses.
Factors affecting households’ seafood purchasing decisions in Auckland, New Zealand: an empirical analysis
Authors: Spinks Aroha , Bose Shekar
Published: March 2003

This paper uses the binary choice model to identify the factors that are significantly influencing the household purchase decisions of seafood products for home consumption in Auckland, New Zealand. It is found that ‘quality’ and ‘cooking easiness’ are the main product attributes that significantly influence households’ choices of seafood in Auckland. Also, the representative household has shown a strong preference for fresh and other alternative seafood products, including processed, smoked and canned, over frozen products. Retail outlets are found to be more attractive to the household purchasing seafood for home consumption. The New Zealand seafood industry may find this baseline study useful as a guide to developing future research structure on the domestic market.
Rennet caseins manufactured from seasonal milks: composition, hydration behaviour and functional performance in pilot‐scale manufacture of mozzarella cheese analogues
Authors: Ennis Michael P , Mulvihill Daniel M
Published: March 2003

Compositional and hydration properties of edible rennet caseins prepared from Irish milks over three production seasons were studied. The ash content of the caseins declined during early to mid‐lactation and increased sharply in late‐lactation. Protein content was independent of season of manufacture, while moisture content showed no clear relationship to season of manufacture. The hydration properties of the rennet caseins on dispersion in a solution of a calcium‐sequestering salt were assessed in a simple model system relevant to mozzarella cheese analogue manufacture. The maximum viscosity index reached and the time taken to reach maximum viscosity index on dispersion of rennet casein both decreased as the season of manufacture progressed. Poor performance of rennet caseins in pilot‐scale mozzarella cheese analogue manufacture was observed for some caseins manufactured from both early lactation milks and late‐lactation milks, while caseins manufactured from mid‐lactational milks generally performed well in pilot‐scale mozzarella cheese analogue manufacture.
Milk sugars and minerals as ingredients
Authors: Harju Matti
Published: March 2003

Lactose is the natural carbohydrate source and prebiotic compound found in the milk of mammals, but large variations in lactase activity in the small intestines of adult populations can cause problems with its use. The value of lactose can be increased by hydrolysis, but even more valuable products can be made by changing the structure of lactose and preventing its absorption in the gut. Some of these nonabsorbable lactose derivatives are already used in medical and functional food applications.

Calcium phosphate precipitation to the heat‐transfer surfaces is one of the oldest problems of the dairy industry, but if precipitation is carried out in controlled conditions, the precipitate can be further processed to form milk calcium powder. Milk calcium can be used as a natural source of calcium in calcium‐fortified dairy products.

The mineral and salty taste of whey has reduced its use as a food ingredient. The use of modern membrane technology offers a means of producing whey salt as a by‐product of whey demineralization. These otherwise wasted minerals can then be used as a natural mineral salt. Especially interesting is the possibility of recycling the whey salt into cheese, improving its nutritional status.
Chemical changes in powdered infant formulas during storage
Authors: Guerra‐Hernández E , Leon C , Corzo N , García‐Villanova B , Romera J M
Published: March 2003

Hydroxymethylfurfural (HMF), furosine (FUR), lactulose (LU), lysine loss, ascorbic acid and colour (ΔE) were determined in powdered infant formulas stored under nitrogen and oxygen conditions at 20°C and 55°CC during 15, 30 and 90 days. The indicators of the assay at 20°C showed similar behaviour in nitrogen or oxygen atmospheres. Changes in furosine and lysine loss after 90 days occurred under oxygen. Storage at 55°C produced considerable browning. Browning was always greater in nitrogen than in oxygen. Most of the studied parameters increased with the storage time and are useful in controlling the extent of browning in powdered infant formulas under adverse storage conditions.
Cottage cheese whey as an ingredient of cottage cheese dressing mixes
Authors: Monsoor M A , Farooq K , Haque Z U
Published: March 2003

The objective of this study was to formulate and develop a good quality cottage cheese dressing using acid whey as the main ingredient. Up to 72% of cottage cheese whey was used in the dressing mixes. The percentage of fat (4.10–5.05%) and total solids (19.41–20.24%) approached the desired level and was within the legal limits for regular cottage cheese. Sensory evaluation scores for flavour, body/texture and appearance were not adversely affected by the use of acid whey. The sensory evaluation scores for all four products made with whey‐ or skimmed milk‐based dressings were higher than the commercial control.
Requirement of Caveolae Microdomains in Extracellular Signal‐Regulated Kinase and Focal Adhesion Kinase Activation Induced by Endothelin‐1 in Primary Astrocytes
Authors: Teixeira Alexandra , Chaverot Nathalie , Schröder Christian , Strosberg A. Donny , Couraud Pierre‐Olivier , Cazaubon Sylvie
Published: March 2003

Abstract : Endothelin‐1 (ET‐1) mitogenic activity in astrocytes is
mediated by the activation of the extracellular signal‐regulated kinase (ERK)
pathway together with the Rho‐dependent activation of the focal adhesion
kinase (FAK) pathway. To clarify the mechanisms responsible for the coordinate
activation of both pathways in the ET‐1 signal propagation, the involvement of
caveolae microdomains, suggested to play a role in signal transduction, was
evaluated. In this study, it is reported that caveolae of primary astrocytes
are enriched in endothelin receptor (ETB‐R). Furthermore, signaling
molecules such as the adaptor proteins Shc and Grb2, and the small G protein
Rho, also reside within these microdomains. Selective disassembly of caveolae
by filipin III impairs the ET‐1‐induced tyrosine phosphorylation of proteins
including ERK and FAK. In agreement with these observations, astrocytes
pretreated with filipin III also failed to form stress fibers and focal
adhesions and did not undergo the associated morphological changes in response
to ET‐1. This study reveals that structural integrity of caveolae is necessary
for the adhesion‐dependent mitogenic signals induced by ET‐1 in astrocytes,
through compartmentation of ETB‐R with the upstream signaling molecules of the ERK and FAK pathways.
Effects of Cyclin‐Dependent Kinase Inhibitors on Transcription and Ocular Circadian Rhythm of Aplysia
Authors: Sankrithi Nagarajan , Eskin Arnold
Published: March 2003

Abstract : Cyclin‐dependent kinases (CDKs) mediate cell‐cycle phase
transitions. Recently, CDKs have been associated with non‐cell‐cycle roles
such as DNA repair, transcription, and phosphate metabolism in yeast. The
cyclical processes, circadian rhythms and the eukaryotic cell cycle, are
similar in many respects. It is possible that a kinase like CDK is involved in
the control of circadian rhythms. In this study, the effects of CDK inhibitors
(olomoucine, roscovitine, and butyrolactone I) on the Aplysia ocular
circadian rhythm were investigated. Continuous treatments with olomoucine (10
μM) lengthened the free‐running period of the rhythm, and pulse
treatments of olomoucine (6 h, 100 μM) delayed the rhythm. The
effects of olomoucine on the rhythm were qualitatively similar to those of a
reversible inhibitor of transcription,
5,6‐dichloro‐β‐1‐ribobenzimidazole. Subsequently, olomoucine was found to
inhibit RNA synthesis in the eye of Aplysia and Bulla. All
of the other CDK inhibitors used in this study also inhibited transcription in
the eye of Aplysia, and their effects on transcription correlated
with their effects on the circadian rhythm. This study adds substantial
evidence to that previously obtained by using
5,6‐dichloro‐β‐1‐ribobenzimidazole for a role of transcription in the
mechanism responsible for circadian rhythmicity in the eye of
Aplysia. Also, these results indicate that caution is warranted in interpreting results obtained by using CDK inhibitors, because these drugs appear to inhibit transcription as well as CDKs.
Light‐Induced Variations in AP‐1 Binding Activity and Composition in the Rat Suprachiasmatic Nucleus
Authors: François‐Bellan A. M. , Deprez P. , Becquet D.
Published: March 2003

Abstract : Expression of immediate early genes, including
fos‐like and jun‐like genes, in the suprachiasmatic nucleus is believed to be part of the mechanism for photic entrainment of circadian rhythms to the environmental light/dark cycle. However, the effects of a light stimulus on activating protein‐1 (AP‐1) complexes in the suprachiasmatic nucleus remain unclear. The photic regulation of AP‐1 DNA‐binding activity and composition in the rat suprachiasmatic nucleus was evaluated by using an electrophoretic mobility shift assay. A light pulse given during subjective night induced an increase in AP‐1 binding activity when either nuclear or whole‐cell extracts from suprachiasmatic nuclei were used. Under constant dark conditions, proteins that are predominant components of AP‐1 complexes are Fra‐2 and Jun‐D. Under light stimulation, c‐Fos and Jun‐B consistently increased, as expected, but this was also the case for Fra‐2, Jun‐D, and c‐Jun, although to a lesser extent. An immunocytochemical study of the Fra‐2 expression pattern demonstrated the presence of the protein in the ventrolateral as well as in the dorsomedial subdivisions of the suprachiasmatic nucleus. Light regulation of Fra‐2 immunoreactivity, however, appeared to be restricted to the ventrolateral subdivision. It is concluded that light may be acting both by increasing constitutive AP‐1 complexes and by inducing the expression of specific complexes.
Mechanism of Thrombin Clearance by Human Astrocytoma Cells
Authors: Mentz Stefani , Lacalle Sonsoles de , Baerga‐Ortiz Abel , Knauer Mary F. , Knauer Daniel J. , Komives Elizabeth A.
Published: March 2003

Abstract : Astroglial cells secrete a variety of factors that contribute to the regulation of neurite initiation and continued outgrowth, among them proteases and protease inhibitors. An alteration in the balance between these proteins has been implicated in Alzheimer's disease, resulting in an accumulation of thrombin : protease nexin 1 (PN1) complexes in the brains of these patients. This report aims at providing a biochemical explanation for this phenomenon. We show that human astrocytoma cells bind and internalize thrombin and thrombin : PN1 complexes efficiently by a PN1‐dependent mechanism. Binding was potently inhibited by soluble heparin and did not occur with the mutant PN1 (K7E) deficient in heparin binding. Receptor‐associated protein, an antagonist of the low‐density lipoprotein receptor‐related protein (LRP), inhibited internalization of thrombin by the astrocytoma cells, but did not affect cell‐surface binding. The results are consistent with a mechanism by which astrocytoma cells clear thrombin in a sequential manner : thrombin is first complexed with PN1, then bound to cell‐surface heparins, and finally internalized by LRP. This mechanism provides a link between the neuronal growth regulators thrombin and PN1 and proteins genetically associated with Alzheimer's disease such as LRP.
Analysis of a Novel Mechanism of Neuronal Toxicity Produced by an Apolipoprotein E‐Derived Peptide
Authors: Moulder Krista L. , Narita Masaaki , Chang Louis K. , Bu Guojun , Johnson Eugene M.
Published: March 2003

Abstract : The apolipoprotein E (apoE)‐derived peptide
(141‐155)2 has a neurotoxic effect, implying that apoE itself could
be a source of toxicity in Alzheimer's disease brain. We characterized the
toxicity of this peptide on superior cervical ganglion (SCG) neurons and
compared the death with the apoptotic death that occurs after nerve growth
factor (NGF) deprivation in these cells. A dose of 10 μM apoE
(141‐155)2 resulted in the death of ~50% of the neurons within 24
h. Nuclear condensation and DNA fragmentation preceded the death. However,
most inhibitors of NGF deprivation‐induced death, including the caspase
inhibitor Boc‐aspartyl(O‐methyl)fluoromethyl ketone and genetic
deletion of bax‐1‐, had no effect on the toxicity.
Inclusion of depolarizing levels of potassium did block the toxicity.
Receptor‐associated peptide (RAP), an antagonist for apoE receptors, did not
protect cells in either SCG or hippocampal cultures. In addition, RAP had no
effect on internalization of the apoE peptide. These data support the
observation that apoE (141‐155)2 is neurotoxic but suggest that the neurotoxicity is distinct from classical apoptosis or necrosis. Furthermore, these results indicate that the toxic effect may occur independently of members of the low‐denśity lipoprotein receptor gene family.