bluuebunny/crossref_metadata_2025 huggingface dataset:
Root architecture and biomass allocation of three range grasses in response to nonuniform supply of nutrients and shoot defoliation
Authors: ARREDONDO J. T. , JOHNSON D. A.
Published: March 2003

Predictions of root architecture have been tested using only a narrow set of environmental conditions and species. There is little information on root architecture of plants growing on semi‐arid grasslands where soil nutrient heterogeneity and defoliation might impose particular restrictions on root growth. We conducted a split‐root study to evaluate the effect of nonuniform nutrient supply and clipping on root architecture and biomass allocation of three range grasses found in the Intermountain West of the USA: ‘Whitmar’, a cultivar of Pseudoroegneria spicata, Bromus tectorum (cheatgrass), and ‘Hycrest’, a hybrid between Agropyron desertorum and A. cristatum. Root systems of individual seedlings were equally divided between the two divisions of a partitioned 10‐l pot, and each of the divisions was independently supplied with ‘high or ‘low’ nutrient solution. Plants were either clipped or not. Characteristics of root architecture (topology and link length), root size (root length and number of root tips), and biomass distribution (specific root length and root mass∶root volume ratio) were evaluated. Root topology (branching distribution) changed with nutrient treatments and defoliation in all three species. Length of links (a segment of root between two branches, or between a node and a root tip) responded to nutrient treatment only in defoliated plants of ‘Whitmar’, in which relative growth rate was associated with changes in architectural traits (external–external and internal–internal link length), while biomass accumulation and relative growth rate in cheatgrass and ‘Hycrest’ maintained allometric relationships with root length. Our results suggest that large plasticity in root architecture, together with inherently low relative growth rate are adaptations that allow ‘Whitmar’ to grow well in heterogeneous and poor soil‐nutrient conditions. Cheatgrass and ‘Hycrest’ exhibited characteristics suggesting capability for rapid exploitation of nutrient patches.
Tansley Review No. 106
Authors: NEWTON RUSSELL P. , ROEF LUC , WITTERS ERWIN , VAN ONCKELEN HARRY
Published: March 2003

For three decades, hypotheses relating to the occurrence and function of cyclic nucleotides in higher plants have been highly controversial. Although cyclic nucleotides had been shown to have key regulatory roles in animals and bacteria, investigations with higher plants in the 1970s and early 1980s were criticized on the basis of (i) a lack of specificity of effects apparently elicited by cyclic nucleotides, (ii) the equivocal identification of putative endogenous cyclic nucleotides and (iii) ambiguity in the identification of enzymes connected with cyclic nucleotide. More recent evidence based on more rigorous identification procedures has demonstrated conclusively the presence of cyclic nucleotides, nucleotidyl cyclases and cyclic nucleotide phosphodiesterases in higher plants, and has identified plant processes subject to regulation by cyclic nucleotides. Here we review the history of the debate, the recent evidence establishing the presence of these compounds and their role; future research objectives are discussed.

contents

Summary

I.
background
427

II.
the history of the debate on camp in plants
431

III.
evidence for the natural occurrence of camp in plants
432

IV.
adenylyl cyclase
435

V.
phosphodiesterases
437

VI.
camp‐dependent protein kinases, creb, camp‐binding proteins and cyclicnucleotide‐gated channels
439

VII.
putative functions of camp
442

VIII.
camp and other cyclic nucleotides
445

IX.
future directions
447

References
449
Characterization of two arbuscular mycorrhizal fungi in symbiosis with Allium porrum: inflow and flux of phosphate across the symbiotic interface
Authors: DICKSON S. , SMITH S. E. , SMITH F. A.
Published: March 2003

Individual arbuscular mycorrhizal fungi can differ markedly in their ability to improve the phosphate nutrition and growth of host plants. In particular, Scutellospora calospora is relatively ineffective with some hosts and a growth depression is often observed. We have examined the abilities of S. calospora and Glomus sp. ‘City Beach’ strain WUM 16, grown in soils which promote extensive mycorrhizal colonization, to transfer phosphate (P) to Allium porrum. Phosphate uptake from the low‐P soils (P0) was compared with uptake from soils amended with extra P (P1). In order to relate P transfer to physiological characteristics of the two fungi, inflow of P via fungus to the plant was combined with the surface areas of intercellular hyphae and arbuscules (symbiotic interfaces) to calculate the amount of P transferred per unit area of interface (P fluxes). ‘Hyphal inflows’ and ‘hyphal fluxes’ were also calculated on the assumption that P uptake by the plant was the same in mycorrhizal and equivalent non‐mycorrhizal (NM) plants (the validity of this assumption is discussed). With both soil P treatments, P was taken up by plants colonized by both mycorrhizal fungi to a greater extent than by the equivalent NM controls. Hyphal inflows to plants in P0 soil that were colonized by Glomus sp. ‘City Beach’ were greatest from 14–21 d and decreased at later harvests. With P1 soil the inflow via Glomus sp. ‘City Beach’ peaked at a very high value at 21–28 d. Hyphal inflows into plants in P0 soil that were colonized by S. calospora increased throughout the experiment, and with P1 soil they remained steady at high values. With both fungi, the surface areas of the symbiotic interfaces increased greatly after 14 d, and generally there was little effect of higher soil P. With P0 soil, Glomus sp. ‘City Beach’ showed no significant differences in the ratio of surface areas of the two interfaces over the course of the experiment. Scutellospora calospora tended to produce a lower percentage of interfacial area contributed by arbuscules. With the mycorrhizal plants growing in their respective soils, there appeared no consistent differences between the two fungi with respect to fluxes of P across the interfaces. With P0 soil, fluxes via Glomus sp. ‘City Beach’ were initially higher than those via S. calospora, but later they were higher with S. calospora. With P1 soil the only difference was the 28–42‐d period, when Glomus sp. ‘City Beach’ produced the higher flux (reflecting the low surface area at the time). The results show that relative inefficiency of S. calospora in its ability to transfer P, as reported by others, may result from different environmental conditions, use of different hosts, or even of different fungal isolates (strains).
A Lycopersicon esculentum phosphate transporter (LePT1) involved in phosphorus uptake from a vesicular–arbuscular mycorrhizal fungus
Authors: ROSEWARNE GARRY M. , BARKER SUSAN J. , SMITH SALLY E. , SMITH F. ANDREW , SCHACHTMAN DANIEL P.
Published: March 2003

In vesicular–arbuscular mycorrhizal symbioses, specialized fungal structures (the arbuscules) are formed which are in intimate contact with plant root cortical cells. It is assumed that these arbuscules are the major sites of solute transfer between the plant and fungus, but there have been no studies that definitively show the extent or types of transfer processes that occur in this structure. Phosphate is one of the major nutrients that is acquired by mycorrhizal fungi and transferred to plants. In this study a single Lycopersicon esculentum cDNA was cloned and shown to be identical to LePT1, a previously cloned inorganic‐phosphate transporter. Expression studies revealed that LePT1 transcript levels remained constant in mycorrhizal plants, but increased in phosphate‐starved, non‐mycorrhizal plants. Localization of the LePT1 transcript by in situ hybridization showed that this gene is highly expressed in arbuscule‐containing cortical cells in mycorrhizal plants. In non‐mycorrhizal plants LePT1 expression was localized to the stele and cortex. The expression studies suggest that this transporter is involved in phosphate nutrition of L. esculentum and its localization in cells that contain arbuscules indicate that it may be the mechanism used by the plant to take up phosphate that is effluxed across the fungal plasma membrane of the arbuscule. Based on our findings and those of others, an integrated model of inorganic phosphate uptake and transfer in mycorrhizal and non‐mycorrhizal plants is presented.
Internal segmentation of rhizomes of Phragmites australis: protection of the internal aeration system against being flooded
Authors: SOUKUP ALEŠ , VOTRUBOVÁ OLGA , ČÍŽKOVÁ HANA
Published: March 2003

Segmentation of the aeration system and its anatomy was studied in rhizomes of common reed (Phragmites australis). Segmentation is achieved by nodal diaphragms which allow the passage of pressurised gas‐flow but which also form effective barriers against flooding of the internal space in case of local injury. The pressures required to force water through the diaphragms were measured and compared with the anatomical structure of the diaphragm. The fine hydrophilic stellate parenchyma of the diaphragms was shown to act as a matrix supporting menisci of air–water interfaces and therefore preventing water movement until the ‘limit’ pressure (measured values ranged from 18 to >40 kPa) was overcome. Although the surfaces of the large stellate parenchyma and sclerenchyma strands covering the diaphragm are hydrophobic these components do little to prevent the ingress of water.
Transport of 15N from a soil compartment separated by a polytetrafluoroethylene membrane to plant roots via the hyphae of arbuscular mycorrhizal fungi
Authors: MÄDER P. , VIERHEILIG H. , STREITWOLF‐ENGEL R. , BOLLER T. , FREY B. , CHRISTIE P. , WIEMKEN A.
Published: March 2003

We studied the transport of 15N from a soil compartment separated from a plant root compartment by a hydrophobic polytetrafluoroethylene (PTFE) membrane to plants in the presence and absence of arbuscular mycorrhizal fungi (AMF). We have previously shown that this type of membrane efficiently inhibits mass flow and diffusion of mobile ions in the soil solution in an abiotic system, but can be penetrated by the hyphae of mycorrhizal fungi. Mycorrhizal tomatoes (Lycopersicon esculentum) colonized by Glomus mosseae were grown at two N fertilizer concentrations in a root compartment. A PTFE membrane was placed between the root compartment and an adjoining soil compartment that was inaccessible to the roots but accessible to the AMF hyphae (hyphal compartment). Additional N was applied to the hyphal compartment using uniformly 15N‐labelled NH4NO3. There was a flux of 15N from the hyphal compartment to the plants even in the absence of mycorrhizal fungi. However, this flux was much higher in mycorrhizal plants, which had much higher N concentrations in their shoots and roots than did the non‐mycorrhizal control plants. This was particularly apparent when the root compartment had a low N fertilizer concentration. Of the total N content of mycorrhizal plants, c. 42 and 24% at the low and high N fertilizer concentrations, respectively, were estimated to originate from the hyphal compartment by transport through AMF hyphae. In the presence of mycorrhizal fungi, the flux of 15N was about three times higher than in their absence. The results show that AMF can access a soil compartment separated by a PTFE membrane, and can contribute substantially to N uptake by plants.
Dynamics of Ni‐based defence and organic defences in the Ni hyperaccumulator, Streptanthus polygaloides (Brassicaceae)
Authors: DAVIS MICHEAL A. , BOYD ROBERT S.
Published: March 2003

Plants use chemical defences to reduce damage from herbivores and the effectiveness of these defences can be altered by biotic and abiotic factors, such as herbivory and soil resource availability. Streptanthus polygaloides, a
nickel (Ni) hyperaccumulator, possesses both Ni‐based defences and organic defences (glucosinolates), but the
extent to which these defences interact and respond to environmental conditions is unknown. S. polygaloides plants
were grown on high‐Ni and low‐Ni soil and concentrations of Ni and glucosinolates were compared with those
of the congeneric non‐hyperaccumulator, S. insignus spp. insignus, grown under the same conditions. Ni contents
were highest (4000 μg g−1 dry tissue) in S. polygaloides plants grown on high‐Ni soil. Glucosinolate content was
significantly higher in S. insignus than in S. polygaloides suggesting that plants defended by Ni produce a lower
concentration of organic defences. In a separate experiment, high‐Ni S. polygaloides plants were exposed to
simulated herbivory or live folivores to determine the inducibility of Ni‐based and organic defences. Contents of
Ni were not affected by either herbivory treatment, whereas glucosinolate concentrations were >30% higher in
damaged plants. We concluded that the Ni‐based defence of S. polygaloides is not induced by herbivory.
The daily integral of growth by Planktothrix rubescens calculated from growth rate in culture and irradiance in Lake Zürich
Authors: BRIGHT DYLAN I. , WALSBY ANTHONY E.
Published: March 2003

In Lake Zürich, populations of the cyanobacterium Planktothrix rubescens develop in the metalimnion during the
summer and become gradually entrained in the deepening surface mixed layer during the autumn. It had
previously been demonstrated that the daily integrals of photosynthetic production accounted for the growth
observed in the metalimnion and greatly exceeded the smaller increase during the autumn. We have now
determined the relationship between growth rate (μ) and irradiance (I) in cultures of P. rubescens strain Pla 9316
maintained at 20 °C on a 12∶12 h light∶dark cycle: the highest net growth rate averaged over the 24 h (μh) was
0.123 d−1, the dark rate (μD) was −0.020 d−1,
the gross rate (φm = μh−μD) was 0.144 d−1,
the affinity coefficient (α) was 0.0273 (d μmol m−2 s−1)−1
and the compensation point (IC) was 1.76 μmol m−2 s−1.
Using the corresponding coefficients calculated for the light period (μLh = 0.267 d−1,
φLm = 0.287 d−1 and αL = 0.0547 (d μmol m−2 s−1)−1),
instantaneous growth rates could be calculated from the irradiance. Comparison with growth rates at 10 °C
indicated a Q10 of 1.48. These coefficients were used in a modification of the Smith equation to calculate potential
growth rates of Planktothrix from the irradiance and temperature at each time and depth in Lake Zürich. Data on
irradiance, vertical light attenuation and temperature were used to calculate the daily integrals of biomass increase
over a period of 136 d. These growth integrals gave a closer correspondence to the observed population increase
than the photosynthetic integrals calculated previously from measurements made with lakewater samples
dominated by Planktothrix. Photosynthetic measurements made with the Planktothrix culture indicated a
maximum rate of carbon increase (0.467 d−1 that exceeds the maximum growth rate, which suggests that other factors limit growth over long periods.
Elevated concentrations of atmospheric CO2 protect against and compensate for O3 damage to photosynthetic tissues of field‐grown wheat
Authors: McKEE I. F. , MULHOLLAND B. J. , CRAIGON J. , BLACK C. R. , LONG S. P.
Published: March 2003

The effects of elevated concentrations of atmospheric carbon dioxide and ozone on diurnal patterns of photosynthesis have been investigated in field‐grown spring wheat (Triticum aestivum). Plants cultivated under
realistic agronomic conditions, in open‐top chambers, were exposed from emergence to harvest to reciprocal
combinations of two carbon dioxide and two ozone treatments: [CO2] at ambient (380 μmol mol−1, seasonal mean)
or elevated (692 μmol mol−1) levels, [O3] at ambient (27 nmol mol−1, 7 hr seasonal mean) or elevated (61 nmol
mol−1) levels. After anthesis, diurnal measurements were made of flag‐leaf gas‐exchange and in vitro Rubisco
activity and content. Elevated [CO2] resulted in an increase in photoassimilation rate and a loss of excess
Rubisco activity. Elevated [O3] caused a loss of Rubisco and a decline in photoassimilation rate late in flag‐leaf
development. Elevated [CO2] ameliorated O3 damage. The mechanisms of amelioration included a protective
stomatal restriction of O3 flux to the mesophyll, and a compensatory effect of increased substrate on photoassimilation and photosynthetic control. However, the degree of protection and compensation appeared to be affected by the natural seasonal and diurnal variations in light, temperature and water status.
Influence of resource unit distribution and quality on the activity of soil fungi in a particulate medium
Authors: GRIFFITH G. S. , BARDGETT R. D.
Published: March 2003

Experiments were set up to assess the relative impacts of grass lamina fragment density, size and quality on the activity and growth of four fungi in a particulate soil‐like matrix. The fungi studied were Cladosporium
cladosporioides, Fusarium lateritium, Phoma exigua and Trichoderma viride, all of which are common inhabitants
of UK upland grassland soils. Resource quality was varied by using three contrasting grasses as sources of lamina
fragments: Lolium perenne, Agrostis capillaris and Nardus stricta. All the fungi were able to forage effectively
through the soil‐like matrix (at a rate of 1–2 ml matrix d−1) and colonize and partially decompose available lamina
fragments (up to 40% d. wt loss). Foraging rates (ml matrix d−1) were affected by lamina fragment species but not
by fragment density or size. In general, F. lateritium and T. viride foraged at a faster rate than the other species. Mycelial activity in the soil‐like matrix was directly proportional to total lamina fragment availability and was unaffected by fragment size. Biomass production on solid media was also directly related to substrate (carbohydrate) availability. The results indicate that these fungi can adjust their growth patterns in response to fragment density so as to maximize foraging efficiency (energy acquired per unit exploratory biomass production). Differences in lamina fragment species were responsible for up to 50% reduction in mycelial activity.
Quantitative genetic analysis of seed vigour and pre‐emergence seedling growth traits in Brassica oleracea
Authors: BETTEY MARY , FINCH‐SAVAGE W. E. , KING G. J. , LYNN J. R.
Published: March 2003

The ability of seeds to germinate and establish seedlings in a predictable manner under a range of conditions has a direct contribution to the economic success of commercial crops, and should therefore be considered in crop improvement. We measured traits associated with seed vigour and pre‐emergence seedling growth in a segregating population of 105 doubled haploid Brassica oleracea lines. The germination traits measured were: mean germination times for unstressed germination; germination under water stress or germination after a heat treatment; and conductivity of seed leachate. The seedling growth traits measured were: seed weight; seedling growth rate; and seedling size at the end of the exponential growth phase. There were some correlations, notably among germination traits, and between seed weight and pre‐emergence seedling growth. Heritability of the various traits was typically in the 10–15% range, with heritability of conductivity and mean germination time under water stress 25 and 24% respectively. Collectively the results indicate that germination and pre‐emergence seedling growth are under separate genetic control. Quantitative trait loci analyses were carried out on all measurements and revealed significant loci on linkage groups O1, O3, O6, O7 and O9. We suggest that genes at these loci are important in determining predictable seed germination and seedling establishment in practice.
Field measurements of root respiration and total soil respiration in an alder forest
Authors: Kutsch Werner L. , Staack Arne , Wötzel Jörg , Middelhoff Ulrike , Kappen Ludger
Published: March 2003

• Variation in root respiration and total soil respiration measured in the field in an alder (Alnus glutinosa) forest is reported here, complementing previous studies of below‐ground carbon relations.

• A novel technique, involving minimum disturbance to the roots, was used to measure tree fine‐root respiration, while soil respiration was measured in an open system using infrared gas analysis. Calculations by process models of both rhizomicrobial, and bulk soil, respiration were compared with measurements of total soil respiration.

• The rhizomicrobial respiration rate was strongly temperature dependent, with the variation determined by fine root structural parameters. The data were used to calibrate a soil respiration model comprising mineralization and rhizomicrobial respiration submodels. The calculated annual rhizomicrobial respiration (1234 g m−2) matched the carbon balance of the alder trees calculated in earlier studies; however, the calculated total annual soil CO2 efflux (1754 g m−2) was very high compared with other European forest sites.

• The modelled total soil respiration fitted well to measured values; a changing groundwater table and modified carbon partitioning of the alder trees might account for deviations during early summer.
Carbon isotope discrimination by Sorghum bicolor under CO2 enrichment and drought
Authors: Williams D. G. , Gempko V. , Fravolini A. , Leavitt S. W. , Wall G. W. , Kimball B. A. , Pinter P. J. , LaMorte R. , Ottman M.
Published: March 2003

Sorghum bicolor was exposed to free‐air CO2 enrichment (FACE) and drought at the Maricopa Agricultural Center, AZ, USA, in summer 1998. We predicted that bundle sheath leakiness (Φ) would be insensitive to FACE under well‐irrigated (wet) conditions, but would be lower in FACE compared with control‐CO2 treatments when irrigation was withheld (dry).

 Leaf and air δ13C values and leaf pi/pa from gas exchange were measured to estimate carbon isotope discrimination (Δ) and F. Midday leaf water potential (Ψ) and photosynthetic rate were simultaneously measured to evaluate the influence of plant water status on Φ and the association between Φ and carbon gain.

 Irrigation treatments affected Ψ, pi/pa, Δ and Φ in control CO2 and FACE rings. Differences in leaf Δ between wet‐ and dry‐treatment plots resulted from changes in Φ and to stomatal influences on pi/pa. FACE had very little effect on Ψ, Δ and Φ in wet‐treatment plots. However, Φ and Δ in dry plots were higher in control than in FACE rings.

 FACE ameliorated the effects of drought on bundle sheath leakiness and Δ by reducing transpiration, prolonging soil water availability and enhancing plant water status. Direct effects of CO2 enrichment on C4 photosynthetic metabolism in Sorghum apparently are minimal and indirect effects depend on soil water supply.
Leaf conductance decreased under free‐air CO2 enrichment (FACE) for three perennials in the Nevada desert
Authors: Nowak Robert S. , DeFalco Lesley A. , Wilcox Carolyn S. , Jordan Dean N. , Coleman James S. , Seemann Jeffrey R. , Smith Stanley D.
Published: March 2003

•  A common response of plants to elevated atmospheric CO2 concentration (CO2) is decreased leaf conductance. Consequently, leaf temperature is predicted to increase under elevated CO2.

•  Diurnal patterns of leaf conductance and temperature were measured for three desert perennials, the C3 shrub Larrea tridentata, C3 tussock grass Achnatherum hymenoides and C4 tussock grass Pleuraphis rigida, at the Nevada Desert FACE facility. Measurements were made on ambient and c. 550 µmol mol−1 CO2 plots through both a wet and dry year.

•  Reductions in conductance were 35%, 20% and 13% for Pleuraphis, Achnatherum and Larrea, respectively. Decreased conductance occurred throughout the day only for Pleuraphis. Both C3 species had smaller CO2 effects during dry periods than wet. Leaf temperature did not differ significantly between elevated and ambient CO2 for any species. Comparisons of blower‐control and nonring plots indicated that the FACE apparatus did not confound our results.

•  All three species exhibited decreased leaf conductance under elevated CO2, although reductions were not uniform during the day or among years. Nonetheless, leaf energy balance was only minimally changed for these microphyllous desert perennials.
Reduced photorespiration and increased energy‐use efficiency in young CO2‐enriched sorghum leaves
Authors: Cousins Asaph B. , Adam Neal R. , Wall Gerard W. , Kimball Bruce A. , Pinter Paul J. , Leavitt Steven W. , LaMorte Robert L. , Matthias Allan D. , Ottman Michael J. , Thompson Thomas L. , Webber Andrew N.
Published: March 2003

To determine the response of C4 plants to elevated CO2 it is necessary to establish whether young leaves have a fully developed C4 photosynthetic apparatus, and whether photosynthesis in these leaves is responsive to elevated CO2.

 The effect of free‐air CO2 enrichment (FACE) on the photosynthetic development of the C4 crop Sorghum bicolor was monitored. Simultaneous measurements of chlorophyll a fluorescence and carbon assimilation were made to determine energy utilization, quantum yields of carbon fixation (φCO2) and photosystem II (φPSII), as well as photorespiration.

 Assimilation in the second leaf of FACE plants was 37% higher than in control plants and lower apparent rates of photorespiration at growth CO2 concentrations were exhibited. In these leaves, φPSII : φCO2 was high at low atmospheric CO2 concentration (Ca) due to overcycling of the C4 pump and increased leakiness. As Ca increased, φPSII : φCO2 decreased as a greater proportion of energy derived from linear electron transfer was used by the C3 cycle.

 The stimulation of C4 photosynthesis at elevated Ca in young leaves was partially due to suppressed photorespiration. Additionally, elevated Ca enhanced energy‐use efficiency in young leaves, possibly by decreasing CO2 leakage from bundle sheath cells, and by decreasing overcycling of the C4 pump.
Carbohydrate metabolism in ectomycorrhizas: gene expression, monosaccharide transport and metabolic control
Authors: Nehls Uwe , Mikolajewski Sabine , Magel Elisabeth , Hampp Rüdiger
Published: March 2003

Ectomycorrhizas are mutalistic symbiotic associations formed between fine roots of higher plants, mostly trees, and a wide range of soil ascomycetes and basidiomycetes. It is commonly accepted that there is mutual benefit to the partners, due to the exchange of plant‐derived carbohydrates for amino acids and nutrients supplied by the fungus. While the major concepts of mycorrhizal functioning (exchange of nutrients and metabolites) were proposed in the 1960s, their verification at the molecular level started approximately 10 years ago. This review covers concepts at the molecular level concerned with the fungal carbohydrate supply in symbiosis. We discuss: strategies used by host plants to compensate (and perhaps restrict) carbohydrate drain to the fungal partner; fungal mechanisms that generate strong monosaccharide sinks in colonized plant roots (the formation of a strong carbohydrate sink is a prerequisite for efficient fungal carbohydrate support by the plant partner); and the impact of apoplastic hexose concentration on the regulation of fungal metabolism in symbiosis, since monosaccharides not only serve as nutrients but also as a signal that regulates gene expression.
Community ecology of ectomycorrhizal fungi: an advancing interdisciplinary field
Authors: Dahlberg Anders
Published: March 2003

A long‐term goal of community ecology is to identify spatial and temporal factors that underlie observed community structures. Ultimately, ecologists seek to relate community patterns to ecosystem processes and functions. Since the mid 1990s, ectomycorrhizal (ECM) research has been equipped with tools to identify and fully quantify the taxonomic diversity in below‐ground ECM fungal communities in detail and address such questions. Many of the most important functions of terrestrial ecosystems, as well as interactions, between plants take place below ground and mycorrhizal fungi are among the key players in soil ecology. Here the rapidly increasing knowledge of ECM fungal community ecology is reviewed and the prospects discussed for elucidating processes that structure ECM fungal communities and the way in which such knowledge might be integrated with, and advance, the understanding of plant ecology and ecosystem processes.
PEP carboxylase kinase is a novel protein kinase controlled at the level of expression
Authors: Nimmo Hugh G. , Fontaine Véronique , Hartwell James , Jenkins Gareth I. , Nimmo Gillian A. , Wilkins Malcolm B.
Published: March 2003

Phosphoenolpyruvate (PEP) carboxylase plays a number of key roles in the central metabolism of higher plants. The enzyme is regulated by reversible phosphorylation in response to a range of signals in many different plant tissues. The data discussed here illustrate several novel features of this system. The phosphorylation state of PEP carboxylase is controlled largely by the activity of PEP carboxylase kinase. This enzyme comprises a protein kinase catalytic domain with no regulatory regions. In many systems it is controlled at the level of expression. In C4 plants, expression of PEP carboxylase kinase is light‐regulated and involves changes in cytosolic pH, InsP3 and Ca2+ levels. Expression of PEP carboxylase kinase in CAM plants is regulated by a circadian oscillator, perhaps via metabolite control. Some plants contain multiple PEP carboxylase kinase genes, probably with different expression patterns and roles. A newly discovered PEP carboxylase kinase inhibitor protein might facilitate the net dephosphorylation of PEP carboxylase under conditions in which flux through this enzyme is not required.
Heterotrimeric G‐proteins in plant cell signaling
Authors: Millner P. A.
Published: March 2003

Heterotrimeric G‐proteins, which couple cell surface receptors with internal effectors, are evident in all eukaryotes. Their operation involves receptor activation, GTP/GDP exchange and modulation of effector activity; deactivation occurs by an intrinsic GTPase activity. Structurally, G‐proteins comprise three dissimilar subunits; Gα, Gβ and Gγ. The Gα subunit consists of an α‐helical and a GTPase domain, the latter is responsible for interaction with Gβγ, receptor and effector. Gβ and Gγ form a tightly associated heterodimer which can also modulate effector activity when released by the activated Gα. Genome sequence and other data suggest that, in plants, there are several (~8–10?) Gα, one or two Gβ and one Gγ. These proteins are expressed throughout the plant, mainly in the plasma membrane and endoplasmic reticulum. In vivo, there is strong evidence for G‐protein control of ion channels, particularly K+, in the response pathways to fungal and bacterial pathogens as well as in some aspects of gibberellin, abscisic acid and auxin signaling pathways. Finally, future prospects for understanding plant G‐protein linked signaling will rely on new and emerging technologies; these include antisense suppression, gene knockouts, yeast two‐hybrid and phage display molecular approaches, intracellular immunization using recombinant single chain antibodies and expression of peptide encoding minigenes.
Vernalization response of wild chickpea
Authors: Abbo S. , Lev‐Yadun S. , Galwey N.
Published: March 2003

• Response to low temperature during early growth in cultivated chickpea (Cicer arietinum) and its wild progenitor C. reticulatum was investigated to clarify the evolutionary processes under domestication in this crop.

• Parental lines and their F2 and F3 progeny were exposed to cold treatment (4°C) for 30°d after seed imbibition and compared with controls.

• Cold treatment caused a 19‐d advance in flowering time in wild chickpea, but only a 3‐d advance in cultivated chickpea. It also promoted apical dominance of the main stem of the wild chickpea, whereas apical dominance was constitutive in the cultivated type. F3 progeny showed significant genetic variation affecting the response of flowering time to low temperature. We suggest that selection against alleles conferring vernalization requirements was a major step in the evolution of cultivated chickpea. The reduced low‐temperature response was fundamental both for the ancient conversion of chickpea from an autumn‐ to a spring‐sown crop (‘summer crop’) in west Asia, and for its spread into the lower‐latitude regions of India and east Africa.

• Attempts to improve yield and/or resistance to biotic and abiotic stresses through introgression with wild chickpea species carry the risk of reintroducing vernalization sensitive alleles into the cultigen.
Extensive tubular vacuole system in an arbuscular mycorrhizal fungus, Gigaspora margarita
Authors: Uetake Y. , Kojima T. , Ezawa T. , Saito M.
Published: March 2003

• A tubular vacuolar system is reported here for the first time in living hyphae of Gigaspora margarita, an arbuscular mycorrhizal fungus, during various phases in the development of a symbiotic relationship with onion (Allium cepa) seedlings.

• Germ tubes, extraradical hyphae and intercellular hyphae were labeled with Oregon Green 488 carboxylic acid diacetate and observed by laser scanning confocal microscopy. Emphasis was placed on the relationship between the shape of vacuoles and the presence of cytoplasmic streaming.

• In germ tubes, labeled vacuoles showed a variety of profiles, including spherical and tubular (< 0.5 µm diameter), with various compositions of these shapes along the length of the germ tubes. The tubular vacuoles rarely interconnected with spherical vacuoles and often formed longitudinally oriented, elongated bundles. The tubular vacuolar system appeared to be associated with cytoplasmic streaming, whereas spherical vacuoles were not. Tubular vacuoles were observed in all regions of the germ tubes and were also observed in both extraradical and intercellular hyphae.

• The results question the hypothesis that discrete vacuoles may be involved in the translocation of polyphosphate along hyphae of arbuscular mycorrhizal fungi.
Occurrence of tetraploid and hexaploid cytotypes between and within populations in Dianthus sect. Plumaria (Caryophyllaceae)
Authors: Weiss Hanna , Dobeš Christoph , Schneeweiss Gerald M. , Greimler Josef
Published: March 2003

The occurrence of both tetraploid and hexaploid cytotypes within and between populations of several species of Dianthus
section
Plumaria was analysed.

Chromosome numbers for 13 populations of eight taxa are presented together with a thorough compilation of previously published data.

Most of the taxa are polyploids (tetraploids and hexaploids). Three groups can be distinguished: (1) only one ploidy level within a taxon; (2) more than one ploidy level, but only single cytotypes within a population; and (3) populations with a cytotype mixture. From some populations, reported earlier to contain tetraploids, we found only hexaploid individuals. Hexaploids occur over the whole range of polyploid taxa, revealing no geographical pattern.

Polyploidy is very likely the result of autopolyploidization, at least for the hexaploid cytotypes, which formed many times independently and occur sympatrically with tetraploids. Most of the populations with mixed cytotypes represent primary hybrid zones. It is not yet possible to decide whether directional (one cytotype will become extinct in the longer term) or balanced selection (both cytotypes can coexist) is acting in those populations.
The nature of value created by UK online grocery retailers
Authors: Bevan Julia , Murphy Ruth
Published: March 2003

The UK retail environment is extremely competitive, forcing retailers to constantly develop and enhance both their offerings and their formats. Probably the most significant changes taking place are coming from not the products being sold themselves, but rather when, how and where they are being sold. For example, new technologies such as the Internet, CD‐Roms, electronic kiosks and digital television are opening up new opportunities for retailers through remote purchasing and delivery. While a number of large retailers have made heavy investments into electronic retailing, such as Arcadia, Marks & Spencer, Tesco and Sainsbury, it is uncertain how they are going to use this technology to gain competitive or market advantages. Given the media attention which technologies such as the Internet has attracted, there is the danger that businesses may adopt an unfocussed use. This report identifies and evaluates the ways in which major UK grocery retailers are using the Internet to create value for their users over and above that which is offered by bricks and mortar stores. Web sites of three grocery retailers were evaluated via preselected criteria in order to assess how they created value for their customers. Applying Holbrook’s typology of consumer value, the findings of the research suggest that each of the retailers surveyed are similar in terms of the nature of the value they have created for consumers online, these being value‐as‐convenience and value‐as excellence.
The role of ethical obligation and self‐identity in ethical consumer choice
Authors: Shaw Deirdre , Shiu Edward
Published: March 2003

Many variables have been proposed as additions to the theory of planned behaviour structure, and evidence exists to support the value of a measure of ethical obligation and self‐identity. Furthermore, some research has suggested that ethical obligation may serve as an antecedent to attitude as well as intention. This paper presents findings from a large scale survey that highlights the usefulness of ethical obligation and self‐identity in the prediction of intention. Additionally, the role of both these variables in the prediction of attitude is also suggested. This is examined within the ‘ethical’ context of fair trade grocery purchases. Methodological implications for further research are discussed.
The UK Food Standards Agency: putting the consumer first
Authors: Webster Jacqui
Published: March 2003

The Food Standards Agency was set up in April 2000 to protect the health of the public and the interests of consumers in relation to food. Its principal purpose is to put the consumer first. But what does this mean in practice? The Agency is finding ways to help consumer organizations and consumer representatives contribute more effectively to its work. However, consumer organizations cannot hope to represent the full range of consumer perspectives, and so the Agency is keen to reach out to individual consumers using a variety of innovative mechanisms. This article will describe why the Agency was established and how it achieves its main objective of putting the consumer first. It will discuss how the Agency is developing and testing new ways of working to ensure that the consumer perspective is fully accounted for when developing and evaluating policies, including setting up an influential new Consumer Committee. It will go on to highlight a number of recent innovative consumer consultations and structures that have been established to involve consumers in Agency policy making. It will discuss these processes and how the lessons that have been learnt are informing future Agency strategies. The article will then describe how the Agency protects consumers through effective risk communication strategies and how its Annual Consumer Attitudes Survey will help it measure success so that it can continue to set new stand‐ards in putting consumers first in relation to food.
A comparative study of eating‐out behaviour between Japan and Korea by fuzzy regression
Authors: Tsutsumi Nobuko , Yong‐Sun Chung
Published: March 2003

The Japanese and Korean dietary styles are the most similar in the world. The dietary changes of two Asian countries, which are concomitant with their economic growth, have also followed a similar course. Exteriorization is progressing in eating habits, which is connected with a change of lifestyle and food consciousness. The environment surrounding consumers is changing, and consumption behaviour is gradually changing too. Generally, human action depends on a subjective judgement and involves uncertainty. The purpose of this paper is to analyse the consumer's eating‐out behaviour from 1976 to 1998 by fuzzy regression, which is able to deal with a vague and uncertain phenomenon, and to show the effect of this method between the two countries. As a result, the fuzzy parameters showed fairly similar trends both in Japan and Korea. The relative price and habit‐formation effect influenced the expenditure of eating‐out directly, whereas income had an indirect influence on eating‐out expenditure. Moreover, Korean consumer behaviour had become much more vague and complicated than that in Japan.
The importance of origin as a quality attribute for beef: results from a Scottish consumer survey
Authors: Davidson Amy , Schröder Monika J.A. , Bower John A.
Published: March 2003

Perception of country of origin and purchasing habits for beef were examined for urban and rural Scottish consumers. Origin was identified as being as important as intrinsic quality cues of colour and leanness, with rural consumers giving more weight to origin than urban ones. Most consumers interpreted ‘Scotch Beef’ and ‘British Meat’ label logos as evidence that the beef animals were ‘born, raised and slaughtered in Scotland or Britain’ respectively. The logos were taken as indicators of quality and safety. Both urban and rural respondents had higher agreement levels with Scotch beef as a safer, higher quality and more expensive commodity than British meat. Rural consumers made more use of butcher shops for purchase, but both groups sought butcher beef for quality reasons and supermarket sources because of convenience.
Consumer socialization, social structural factors and decision‐making styles: a case study of adolescents in Malaysia
Authors: Kamaruddin Abdul Razak , Mokhlis Safiek
Published: March 2003

The purpose of this study is to investigate how the process of consumer socialization will determine adolescents’ decision‐making styles. Eight decision‐making styles were conceptualized as outcomes of the socialization process, which is acquired via interaction with socialization agents, namely parents, peers, printed media, television commercials and in‐school education. The study also proposed five social structural variables (social class, gender, ethnicity, residence and religion) as being associated with the socialization agents and decision‐making styles. The study sample consisted of 934 adolescents between the ages of 16 and 19 years. The data were collected using a self‐administered questionnaire and analysed with the SPSS computer program. As a result of regression analyses, significant relationships were found between social structural factors and socialization processes, suggesting that the influence of socialization agents on adolescents may vary according to certain demographic characteristics. Significant relationships were also found between social structural factors and socialization processes. Peers appeared to be the most important agents of consumer socialization, contributing to a variety of desirable as well as undesirable consumer decision styles. Printed media and television commercials were also found to be significant sources of the acquisition of both desirable and undesirable decision‐making styles. Parents and in‐school education, however, were insignificant in the acquisition of any decision‐making styles among adolescents. Information obtained from this study could be useful to government agencies and consumer educators. The most revealing finding of this study is that parents did not contribute to the formulation of decision‐making orientation for adolescents. This points to the need for consumer educators to take steps in designing programmes that will involve parents as primary socialization agents at home; this may be facilitated via printed materials. Apart from this, the information can also be helpful in enabling marketers to be more effective in targeting various adolescent markets by formulating marketing strategies according to demographic factors, socialization process and decision‐making styles.
Edible table (bio)spread containing potentially probiotic Lactobacillus and Bifidobacterium species
Authors: Charteris William P , Kelly Phillip M , Morelli Lorenzo , Collins J Kevin
Published: March 2003

A prototype of a reduced fat (60% w/w) edible table biospread, with an added viable, nongrowing, mixed‐strain and potentially probiotic culture was developed. Conventional commercial aqueous‐phase ingredient and reduced fat spread processing technologies were modified to achieve acceptable strain viability (
≥ 105 cfu/mL) during scraped‐surface heat exchange emulsion processing and biospread shelf life. The modifications consisted of:

 spilt‐stream pasteurization of the aqueous and lipid phases (thereby obviating the need for in‐line pasteurization of the water‐in‐oil emulsion during processing);

reduction of the second scraped‐surface tube‐chiller A‐unit agitation rate (thereby achieving a biphasic moisture droplet size distribution in the product);

emulsification, processing and packaging under oxygen‐free nitrogen (thereby creating anaerobic conditions within the product);

employing a near‐neutral pH, multicomponent, structured, hydrocolloid‐stabilized aqueous phase.

The viability of added bifidobacteria was markedly less than that of lactobacilli, in spite of the biospread ingredient and processing modifications employed. It is advocated that further improvement of bifidobacteria viability is warranted before progressing to the validation of biological properties in vivo and making a commercial biospread available to the consumer.
A study of the growth of Lactobacillus acidophilus in bovine, ovine and caprine milk
Authors: Drakoularakou Alexandra P , Kehagias C , Karakanas P N , Koulouris S , Timbis D
Published: March 2003

The fermentation of reconstituted bovine, ovine and caprine milks with Lactobacillus acidophilus was investigated. Better growth of Lb. acidophilus was observed in ovine milk, but higher acidities developed in caprine milk. The high acidity produced after 12 h of fermentation (pH 3.9) created a hostile environment for the survival of the microorganism in caprine milk.
Health library partnership programmes between resource‐poor countries and Western Europe
Authors: Shaw Jean G.
Published: March 2003

A survey of health library partnerships between the UK and northern European countries and African or eastern European countries was undertaken to complement a similar survey of 24 North American health libraries. Out of 11 partnerships described, six provided sufficient data to be included in a quantitative analysis. These results give some baseline data about such partnerships and their activities, reasons for success and problems encountered. Some libraries have little involvement other than sending duplicate books and journals; others are more deeply involved in all aspects of library activity including professional development. Good communications, both human and technological, are important for maintaining partnership momentum. Staff commitment on both sides and institutional support for the partnership are essential, especially when programmes have costs which must be met either by the institution or outside funders. The financial consequences of partnership may inhibit their initiation, but successful partnerships with demand driven programmes bring benefits to both sides.