bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of fructans by partially purified fructosyltransferase activities from Lolium rigidum
Authors: ST. JOHN J. A. , SIMS I. M. , BONNETT G. D. , SIMPSON R. J. 
Published: March 2003

Sucrose∶sucrose fructosyltransferase (SST) activity was partially purified from whole shoots of Lolium rigidum by a combination of affinity chromatography, gel filtration and anion‐exchange chromatography. The SST activity co‐eluted with some fructan∶fructan fructosyltransferase (FFT) and invertase activities and consequently the partially purified preparation was termed the fructosyltransferase (FT) preparation.The SST‐like activity in the FT preparation was purified 214‐fold and had an apparent molecular mass of 84000. The FT preparation contained several peptides with an apparent pI of 4·6–4·7. When assayed with sucrose concentrations up to 600 mM, the FT preparation synthesized 1‐kestose at all concentrations, and synthesized 6‐kestose at concentrations of 150 mM and greater. The Km of 1‐kestose production was 0·2 M. When the FT preparation was assayed at a concentration of activity approximately half that measured in fresh tissue with 100 mM sucrose, 1‐kestose, or 6G‐kestose as substrates, fructans of degree of polymerization (DP) 5 were synthesized.A partially purified FFT activity, free of SST and invertase activities, which synthesized β‐2,1‐glycosidic linked oligofructans of DP 6, was combined in vitro with the FT preparation (FFT‐FT preparation) to give a ratio of SST∶FFT activities similar to that measured in crude enzyme extracts from L. rigidum. The FFT‐FT preparation synthesized oligofructans when assayed with 100 mM concentrations of sucrose, 1‐kestose or 6G‐kestose, but was not able to synthesize fructans of DP 6 even after extended assays of up to 10 h. The FFT‐FT preparation was also assayed with 100 mM sucrose with small amounts of concentrated sucrose added periodically during the assay to maintain the substrate concentration. In this assay, the FFT‐FT preparation synthesized fructans up to an apparent DP of 17 or greater. The fructans of DP 6 synthesized in the assay appeared to form two molecular series containing both β‐2,1‐ and β‐2,6‐glycosidic linked fructosyl residues with terminal or internal glucosyl residues. The apparent rate of SST activity in the assay of the FFT‐FT preparation was greater than that measured in a similar assay of the FT preparation alone which did not result in fructans with DP 6. It was concluded that the FFT‐FT preparation, when assayed with a continual supply of sucrose, contained a factor which promoted synthesis of fructans of DP 6 and synthesis of β‐2,6‐glycosidic linkages between fructosyl residues.
Thioredoxins: structure and function in plant cells
Authors: JACQUOT JEAN‐PIERRE , LANCELIN JEAN‐MARC , MEYER YVES 
Published: March 2003

SUMMARYThioredoxins are ubiquitous small‐molecular‐weight proteins (typically 100–120 amino‐acid residues) containing an extremely reactive disulphide bridge with a highly conserved sequence ‐Cys‐Gly(Ala/Pro)‐Pro‐Cys‐. In bacteria and animal cells, thioredoxins participate in multiple reactions which require reduction of disulphide bonds on selected target proteins/ enzymes. There is now ample biochemical evidence that thioredoxins exert very specific functions in plants, the best documented being the redox regulation of chloroplast enzymes. Another area in which thioredoxins are believed to play a prominent role is in reserve protein mobilization during the process of germination. It has been discovered that thioredoxins constitute a large multigene family in plants with different‐subcellular localizations, a unique feature in living cells so far. Evolutionary studies based on these molecules will be discussed, as well as the available biochemical and genetic evidence related to their functions in plant cells. Eukaryotic photosynthetic plant cells are also unique in that they possess two different reducing systems, one extrachloroplastic dependent on NADPH as an electron donor, and the other one chloroplastic, dependent on photoreduced ferredoxin. This review will examine in detail the latest progresses in the area of thioredoxin structural biology in plants, this protein being an excellent model for this purpose. The structural features of the reducing enzymes ferredoxin thioredoxin reductase and NADPH thioredoxin reductase will also be described. The properties of the target enzymes known so far in plants will be detailed with special emphasis on the structural features which make them redox regulatory. Based on sequence analysis, evidence will be presented that redox regulation of enzymes of the biosynthetic pathways first appeared in cyanobacteria possibly as a way to cope with the oxidants produced by oxygenic photosynthesis. It became more elaborate in the chloroplasts of higher plants where a co‐ordinated functioning of the chloroplastic and extra chloroplastic metabolisms is required.CONTENTSSummary543I.Introduction544II.Thioredoxins from photosynthetic organisms as a structural model545III.Physiological functions552IV.The thioredoxin reduction systems556V.Structural aspects of target enzymes558VI.Concluding remarks563Acknowledgements564References564
Effect of aluminium on ion uptake and H+ release by maize
Authors: CALBA HENRI , JAILLARD BENOÎT 
Published: March 2003

summaryThe aim of this study was to quantify the long‐term effects of Al in solution on mineral ion uptake and associated H+ release by the roots of maize cultivated in conditions compatible with field data. Two maize (Zea mays L.) cvs of differing sensitivity to Al were compared. The culture was conducted in hydroponic conditions for culture periods of 2–5 d in the presence of 0–30 μM Al. Proton fluxes were localized along the roots using a videodensitometry method with bromocresol green on agarose gel.Aluminium reduced the uptake of anions, particularly NO3−, whereas the uptake of K+ and NH4+ was unaffected. These effects were accompanied by an increase in net H+ release which was quantitatively comparable with the reduction in NO2− uptake. The reduction in NO3− uptake and the concomitant increase in H+ release increased with the quantity of Al accumulated in the roots, which was itself dependent on the concentration of Al in solution. The Al‐sensitive cultivar bound more Al to its roots than the Al‐tolerant one; the reduction in NO3− uptake and the increase in H+ release were also greater in the Al‐sensitive cv. Dye indicator videodensitometry showed that the increased H+ release was general all along the roots.These results led us to specify the relation between the Al deposition in roots, the reduction in NO3− uptake and the stimulation in rhizosphere acidification by the plants. They show that, with maize, Al induces an inhibition in NO3− uptake and an increase in net H+ release in a 1:1 ratio. These concomitant effects suggest that inhibition in NO3−/OH− exchange unmasks active H+ excretion which is otherwise insensitive to Al. Both these effects are closely related to the Al content in roots expressed per unit root length.
Uptake and fate of gaseous pollutants in leaves
Authors: CAPE J. N. 
Published: March 2003

The final paper of the Symposium (delivered by Professor Raven) reviewed the rôle of nitrogen in the development of terrestrial life, and gave a timely reminder of the context of the current debate on the effects of anthropogenic N; current man‐made perturbations of the N cycle are approaching the scale of catastrophic perturbations caused by major meteorite impacts.Faced with such a stark evaluation of the current position one is forced to consider how the scientific community is reacting to the challenge of understanding and predicting the effects of man's activities.
Atmospheric ammonia and impacts of nitrogen deposition: uncertainties and challenges
Authors: SCHJØRRING JAN K. 
Published: March 2003

Dr Willem Asman concluded that the major global sources of atmospheric NH3 are excreta from domestic animals and fertilizers. A question raised was: how reliable are the emission estimates and extrapolations? The answer was that emission estimates are surrounded by uncertainty, which is a major handicap to sound modelling of NH3 dry deposition and, consequently, to obtaining good estimates of critical load exceedences.Major uncertainties in emission estimates seem to be related to the use of simple emission factors, many of which are highly empirical or have been derived from measurements carried out under conditions which deviate considerably from those following modern practices of handling and applying manure and fertilizers. An example is provided by the commonly used emission factors for synthetic fertilizers (see e.g. Bouwman et al. (1997)), which are much higher than recent micrometeorological assessments seem to suggest. Thus, emission from urea, the most widespread fertilizer used in the world (currently around 55% of world N consumption) can be completely avoided if the fertilizer is incorporated into the upper soil layers. Similarly, a growing crop can reduce losses to well below 10% of the applied amount of urea‐N, i.e. to less than half of the generally used emission factors of 15% for Europe and 25% for the tropics. The emission factor for NPK‐fertilizer is set at 4%, whereas that for pure calcium‐ammonium‐nitrate, the same N compound as is present in NPK‐fertilizers, is assumed to be only 2%.
Nitrogen deposition and ectomycorrhizas
Authors: WALLENDA THOMAS , KOTTKE INGRID 
Published: March 2003

As a result of increasing anthropogenic nitrogen deposition, N availability in many forest ecosystems, which are normally N‐limited, has been enhanced. We discuss the impacts of this increased N availability on the ectomycorrhizal (ECM) symbiosis which is generally regarded as an adaptation to nutrient limited conditions. Nitrogen deposition can influence fruit‐body formation by ECM fungi, the production and distribution of the extraradical mycelium in the soil and the formation of ectomycorrhizas.Available data from long‐term N deposition studies indicate that the most prominent effects might be discernible above‐ground (i.e. on the formation of fruit bodies). ‘Generalist’ species, forming a symbiosis with a wide range of tree species, seem to be less affected by increased N availability than ‘specialist’ species, especially those living in symbiosis with conifers. However, the importance of below‐ground investigations to determine the impacts of N deposition on the ECM symbiosis must not be underestimated. Culture experiments show an optimum N concentration for the formation of extraradical mycelium and mycorrhizas. Often, negative effects only become visible at comparatively high N concentrations, but the use of a few easily cultivated species of ECM fungi, which are adapted to higher N concentrations, undermines our ability to generalize.So far, N deposition experiments in the field have only shown minor changes in the below‐ground mycorrhizal population, as estimated from the investigation of mycorrhizal root tips. However, effects on the ECM mycelium, which is the main fungal component in terms of nutrient uptake, cannot be excluded and need further consideration.Because the photoassimilate supply from the plant to the fungal partner is crucial for the maintenance of the ECM symbiosis, we discuss the possible physiological implications of increasing N inputs on the allocation of C to the fungus. Together with ultrastructural changes, physiological effects might precede obvious visible changes and might therefore be useful early indicators of negative impacts of increasing N inputs on the ECM symbiosis.
The role of mycorrhiza in determining the response of Plantago lanceolata to CO2 enrichment
Authors: ROUHIER HERVÉ , READ DAVID J. 
Published: March 2003

Plantago lanceolata L. was grown for 104 d with (M) or without (NM) arbuscular mycorrhizal colonization under conditions of ambient (CAMB=350 μl l−1) and elevated (CELEV=540 μl l−1) CO2. Sequential harvests (H) were taken at 41 (H1), 76 (H2) and 104 d (H3) to determine the time‐course of mycorrhizal influence on the response of the plant to CO2 enrichment. Total yields of M plants were greater than those of NM from H2 onwards. Plants in the MELEV treatment were significantly larger than those in the MAMB at 104 d. There were significant but much smaller differences in yield between NMELEV and NMAMB. The differences in total yield arose through impact of CELEV on both shoots and roots. Total root length was greater in MELEV than in MAMB only at H3, but total length of mycorrhizal root was greater at H2 and H3. The percentages of root length colonized and that occupied by arbuscules and vesicles were greater in MELEV than in MAMB at the last two harvests, indicating increased sequestration of carbon in internal fungal structures. Though extraradical hyphal lengths were greater in MELEV than in MAMB at H2 and H3, the differences were not significant. Phosphorus inflow and P content of M plants were higher than those of NM plants at H2 and H3, and were higher in MELEV than in MAMB at H3. anova revealed no significant interactions between CO2 and mycorrhizal treatment.The results are discussed in relation to carbon sequestration in mycorrhizal systems and likely impacts of CO2 enrichment on P. lanceolata grown under field conditions. The importance of sequential harvesting for realistic determination of responses to CO2 is stressed.
Comparative study of two spruce species in a polluted mountainous region
Authors: Soukupová J. , Rock B. N. , Albrechtová J. 
Published: March 2003

Summary

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

Summary 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

SummaryThe 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

SummaryHere, 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

AbstractDespite 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

AbstractEven 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

AbstractThis 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.
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.