bluuebunny/crossref_metadata_2025 huggingface dataset:
Above‐ground competition does not alter biomass allocated to roots in Abutilon theophrasti
Authors: CASPER BRENDA B. , CAHILL JAMES F. , HYATT LAURA A.
Published: March 2003

We tested whether plants allocate proportionately less biomass to roots in response to above‐ground competition as predicted by optimal partitioning theory. Two population densities of Abutilon theophrasti were achieved by planting one individual per pot and varying spacing among pots so that plants in the two densities experienced the same soil volume but different degrees of canopy overlap. Density did not affect root∶shoot ratio, the partitioning of biomass between fine roots and storage roots, fine root length, or root specific length. Plants growing in high density exhibited typical above‐ground responses to neighbours, having higher ratios of stem to leaf biomass and greater leaf specific area than those growing in low density. Total root biomass and shoot biomass were highly correlated. However, storage root biomass was more strongly correlated with shoot biomass than was fine‐root biomass. Fine‐root length was correlated with above‐ground biomass only for the small subcanopy plants in crowded populations. Because leaf surface area increased with biomass, the ratio between absorptive root surface area and transpirational leaf surface area declined with plant size, a relationship that could make larger plants more susceptible to drought. We conclude that A. theophrasti does not reallocate biomass from roots to shoots in response to above‐ground competition even though much root biomass is apparently involved in storage and not in resource acquisition.
The δ15N of lettuce and barley are affected by AM status and external concentration of N
Authors: AZCÓN‐G.‐AGUILAR ROSARIO , HANDLEY L. L. , SCRIMGEOUR C. M.
Published: March 2003

Mean δ15N of whole‐plants of lettuce and barley varied by 3‰ when given a chemically and isotopically uniform N source. This variation was related to the presence, absence and species of arbuscular mycorrhizal (AM) fungi and to external N concentration. A highly AM‐susceptible plant (lettuce) responded to treatments differently than a less susceptible one (barley). The largest change in whole plant δ15N was related to the experimental combination most likely to be found in field conditions: species of fungus interacting with varying external concentrations of N.

The mechanisms underlying observed variations of plant δ15N are not understood, nor can they be approached directly using δ15N. However, descriptive data, such as presented here, are important to the development of a mechanistic model, because they suggest relationships for future research, using inter alia15N‐enriched tracers. They also confirm that plant N sources, cannot be identified using plant δ15N, even when the type of mycorrhizal association (endo vs. ecto) is known.
Improvement of the 15N dilution method for estimation of absorption of NOx by plants supplied with 15N‐labelled fertilizer
Authors: QIAO Z. , MURRAY F.
Published: March 2003

To develop further the methods for estimation of NOx absorption by plants supplied with 15N‐labelled fertilizer, we proposed a new calculation method, total N fixed method (TNF), and compared with the 15N dilution method and the classical mass balance method (MB).

Hydroponically grown soybean plants were supplied with 15N‐labelled nitrate and exposed to 200–250 nl l−1 NO2 for 7 d. The proportions of the N derived from NO2 to total N in exposed plants were estimated by the three methods.

The reported rates of NO2 absorption by several plant species, estimated by the 15N dilution method, were recalculated using the TNF method. The results of the two methods were compared and showed that: (1) The 15N dilution method overestimated the content of NO2‐N in exposed plants compared with the MB method whilst the TNF method produced estimations of NO2‐N closer to those by the MB method when the plants were supplied with 5 mM nitrate.
(2) The differences in estimations between the MB method and either the 15N dilution method or the TNF method increased with decreasing supply of 15N‐labelled nitrate to roots.
Host–pathogen relationship between Salix and Melampsora sheds light on the parentage of some biomass willows
Authors: PEI M. H. , HUNTER T. , ROYLE D. J.
Published: March 2003

The association between willow (Salix) and rust (Melampsora) is highly specific. Willows named Salix burjatica, S. dasyclados (S.×dasyclados) and S.×calodendron are important in renewable‐energy plantations in the UK and western Europe. There has been much controversy over their origin, species status and nomenclature. It has been suggested that they have originated from hybridization between. S. caprea, S. viminalis and S. cinerea. In the present work, 59 willow clones were investigated through morphological examination and detached leaf inoculation using willow differentials, for their association, in southwest England, with M. capraearum and three pathotypes of Melampsora epitea (Me‐A, B and C). M. capraearum was found on all clones of S. caprea and its hybrids with S. aurita; Me‐A on all S. viminalis clones; Me‐B on wild S. cinerea, S.×calodendron, S.×dasyclados‘De Biardii 445’ and S. ‘Spaethii’; Me‐C on all S. burjatica clones and most S.×dasyclados clones. Both M. caprearum and Me‐A infected all S.×sericans (S. caprea×viminalis) clones and S.×dasyclados‘LA041/03’. We suggest that S.×dasyclados‘LA041/03’ should be treated as S.×sericans (S. caprea×S. viminalis); S. burjatica, S. dasyclados and S.×dasyclados as synonyms; S.×dasyclados‘De Biardii 445’ as S.×calodendron‘De Biardii 445’; and S. ‘Spaethii’ as S.×calodendron‘Spaethii’.
Uptake and utilization of atmospheric ammonia in three native Poaceae species: leaf conductances, composition of apoplastic solution and interactions with root nitrogen supply
Authors: HANSTEIN S. , MATTSSON M. , JAEGER H.‐J. , SCHJOERRING J. K.
Published: March 2003

The physiological potential for acquisition of atmospheric ammonia (NH3) was investigated in three European meadow grasses (Arrhenatherum elatius, Bromus erectus and Brachypodium pinnatum) competing in chalk grasslands. Experiments were carried out with plants cultivated for about three months on a soil–sand mixture at high root nitrogen supply or in nutrient solutions at low root nitrogen supply. Two different root nitrogen regimes were applied to the solution‐grown plants: 130 μmol NO3 plant−1 wk−1 (approx. 50 kg nitrogen ha−1 in three months); or 130 μmol NO3− plus 130 μmol NH4+ plant−1 wk−1. Each regime was combined with two levels of NH3 fumigation (0 and 70 nmol mol−1 air for 24 d). Uptake of gaseous NH3 in the shoots was investigated under controlled environmental conditions including NH3 concentrations ranging from 0 to 30 nmol mol−1 air. Concurrently, photosynthesis, glutamine synthetase activity, nitrogen allocation, biomass allocation and apoplastic cation composition were measured. For A. elatius, the influence of photorespiration on NH3 acquisition was also assessed. Independently of plant nitrogen status, ammonia compensation points in A. elatius and B. erectus plants were <0.5 nmol mol−1. The total leaf conductance to NH3 absorption remained constant at increasing NH3 concentrations, showing that the capacity for assimilation was unaltered. Whereas internal factors in the leaves did not cause differences in the potential for NH3 acquisition between the species, other factors of NH3 acquisition were quite different: B. erectus had higher stomatal conductance and, thus, higher NH3 uptake rates per unit leaf area compared to A. elatius and B. pinnatum; higher stomatal conductances of B. erectus were to a large extent offset by a lower leaf area per plant, resulting from a lower growth rate and thicker leaves than in the two other species. The rate of photorespiration in Arrhenatherum constituted at least 15% of the net photosynthetic rate. Surprisingly, suppression of photorespiration indicated that NH3 uptake was supported by photorespiration. Bromus responded to fumigation with 70 nmol NH3 mol−1 air for 24 d by lowering the root∶shoot ratio and increasing the nitrogen concentration in the stem dry matter. The total leaf conductance to NH3 uptake decreased in all three species upon exposure to NH3, while the stomatal conductance was unaffected. The NH3
exposure caused lower apoplastic concentrations of H+, Mg2+ and Ca2+ in A. elatius and B. erectus.
Molecular investigation of genet distribution and genetic variation of Cortinarius rotundisporus in eastern Australian sclerophyll forests
Authors: SAWYER N. A. , CHAMBERS S. M. , CAIRNEY J. W. G.
Published: March 2003

The size and distribution of Cortinarius rotundisporus genets at three sclerophyll forest field sites in New South Wales, Australia, were estimated by using microsatellite‐primed PCR (MS‐PCR) of DNA extracted from sporocarp tissue. MS‐PCR fingerprints generated with the primers (GTG)5 and (GACA)4 indicated that two to five genets were present at each site, with each site being characterized by a single large genet (9–30 m in diameter). Analysis of internal transcribed spacer (ITS)‐RFLP patterns from individual sporocarps used in the study suggested that three distinct RFLP types were present in the sampled C. rotundisporus population. ITS sequence data indicate that the three RFLP types had less than 88.4% sequence identity to each other, strongly suggesting that C. rotundisporus is a complex of three species.
Nitrogen reserve status affects the dynamics of nitrogen remobilization and mineral nitrogen uptake during recovery of contrasting cultivars of Lolium perenne from defoliation
Authors: LOUAHLIA S. , MACDUFF J. H. , OURRY A. , HUMPHREYS M. , BOUCAUD J.
Published: March 2003

Nitrogen (N) allocated to leaf growth in forage grasses and legumes following severe defoliation is predominately mobilized from the remaining root and leaf sheath tissues, since both N uptake from the soil and N2 fixation are severely down‐regulated for several days. The hypothesis that a low N reserve status at the time of defoliation limits N remobilization and leaf regrowth was tested with contrasting cultivars of Lolium perenne (cvs Aberelan and Cariad) in flowing solution culture. Plants were grown under ‘high’ or ‘low’ (uptake of N decreased by 50%) regimes of N supply for 10 d before a single severe defoliation. Labelling with 15N was used to assess the importance of N reserves, including putative vegetative storage proteins, relative to N translocated from concurrent uptake, as a source of leaf N during regrowth. Leaf regrowth, N uptake and N mobilization were all affected by previous N supply. Low plant N status at the time of defoliation increased regrowth dry weight of ‘Aberelan’ by 10% and translocation of N absorbed from the medium by 23%, while mobilization of N reserves was decreased by 56%. On the contrary, regrowth dry weight of ‘Cariad’ was decreased by 23%, and translocation of N absorbed by 21% in low plant N status, compared with high plant N status. Concentrations of soluble protein in roots and remaining leaf sheaths decreased after defoliation in plants only under optimal N supply. Analysis of soluble proteins in sheath material by SDS–PAGE suggested that three polypeptides (55, 36.6 and 24 kDa) might function as vegetative storage proteins, although they were of low abundance in plants, subjected to monthly harvests, grown in controlled conditions and in the field. The apparent antagonism between uptake of NH4+ or NO3− by roots and mobilization of N reserves is discussed together with evidence for functional vegetative storage proteins in L. perenne.
Specific leaf area in barley: individual leaves versus whole plants
Authors: GUNN S. , FARRAR J. F. , COLLIS B. E. , NASON M.
Published: March 2003

We have explored the relationships between specific leaf area calculated for a whole plant and its individual leaves. Barley was grown in hydroponics in controlled environment cabinets. Plants were harvested on the basis of physiological age (defined as the number of days after full expansion of leaves on the main stem) and the area and weight of whole, fully expanded, leaves measured and specific leaf area (SLA) of individual leaves or whole plants calculated. Specific leaf area calculated for individual leaves (SLAL) varied with leaf position and with leaf age after full expansion whereas SLA calculated for whole plants (SLAP) varied with plant age. The same conclusions were reached whether the results were based on total dry weight or dry weight minus soluble carbohydrates (‘structural weight’). Transferring plants to shade on the day of full expansion of the third leaf on the main stem increased the SLAP, and also SLAL of leaves 3 and 4 on the main stem (leaf 4 being the younger leaf of the two), because of a decrease in the ‘structural weight’ of these leaves. However SLAL of leaf 2 (which was older than leaf 3) was not affected by shading; the effect was confined to leaves developing in the new conditions.
The expression of histone 2A in onion (Allium cepa) during the onset of dormancy, storage and emergence from dormancy
Authors: CARTER CAROL E. , PARTIS MICHAEL D. , THOMAS BRIAN
Published: March 2003

The tissue‐specific and developmental expression of histone 2A was studied in onion (Allium cepa‘Robusta’), using northern blots. Histone 2A expression was enriched in basal tissues, particularly in the inner, meristematically active parts of bulbs. The expression was assessed during a time course of bulb development, dormancy onset and post‐harvest sprouting in field‐grown material. During bulb development histone 2A expression in the inner bulb declined rapidly during bulb ripening, reaching a minimum with the onset of dormancy. During post‐harvest storage, expression increased slowly, reaching a peak in the spring, coinciding with the first observed sprout emergence. It was concluded that in onion, as in other plant systems, histone 2A expression is linked to cell division and dormancy level, the peak in expression during post‐harvest storage indicating the time of dormancy breakage. In cultivars where post‐harvest sprouting occurred much earlier or much later than in ‘Robusta’, this expression peak occurred at about the same time of year, regardless of sprouting time. It was concluded that differences in storage longevity between cultivars were not due to differing times of dormancy breakage. Factors controlling the rate of sprout emergence post‐dormancy are likely to be major determinants of storage capacity.
The dendrochronological potential of modern yew (Taxus baccata) with special reference to yew from Hampton Court Palace, UK
Authors: MOIR A. K.
Published: March 2003

Modern yew (Taxus baccata) is demonstrated to have considerable potential for dendrochronological use. A replicated 303 yr chronology has been formed from Hampton Court Palace yew and cross‐matches well with a number of different tree species, including oak. Growth is positively correlated with rainfall but inversely related to late summer temperature. Range limits and present and prehistoric sources of yew are also briefly discussed, highlighting the future potential of yew to become the third major tree species for British dendrochronological study.
Diaphragms and flooding survival
Authors: Armstrong W.
Published: March 2003

Why don't the gas spaces of submerged organs of wetland plants flood extensively when damaged? In addressing this intriguing question, Soukup et al. (pp. 71–75 in this issue) report on the role of rhizome diaphragms as barriers to flooding in Phragmites australis. This should prompt some reappraisal of the ways in which flooding resistance can be realized, even perhaps in undamaged organs.

Most emergent wetland macrophytes have an abundance of interconnected internal gas space, much of it in the form of large voids transversely partitioned at intervals by perforated cellular plates termed diaphragms. Functionally, it provides a low‐resistance pathway for internal oxygen transport to support the respiratory needs of submerged and buried organs (Armstrong, 1979; Armstrong et al., 1988; Crawford, 1992) and facilitates carbon dioxide removal. However, it does more than this, since it enables oxygen to be released from the root to where it can support aerobic microbial activity in otherwise anaerobic sediments, and phytotoxin immobilization or destruction (Armstrong et al., 1992; Begg et al., 1994; Gilbert & Frenzel, 1998). This oxygen release is regarded by some as a valuable aid to effluent purification by constructed wetlands. Perhaps a less desirable property of this gas‐space provision is its recently discovered role in enhancing the emissions of greenhouse gases such as methane from wetlands (Brix et al., 1992; Chanton & Whiting, 1996; Crutzen, 1991; Dacey & Klug, 1979).
Tansley Review No. 109.
Authors: COGDELL R. J. , LINDSAY J. GORDON
Published: March 2003

This review sets out the case that now is the time for plant science to establish the technologies required for routinely studying the structure and function of plant proteins. The impact that protein structural information can have is illustrated here with reference to photosynthesis. Our understanding of the precise molecular mechanisms of the light‐reactions of photosynthesis has been transformed by the combination of high‐resolution protein structural data and detailed functional studies. The past few years have been a particularly exciting time to be engaged in basic plant science research. The application of modern techniques of molecular biology has allowed many key questions to be addressed. The stage is now set for an even bigger revolution as the current plant genome sequencing projects are completed. If these advances are going to be fully exploited, plant science must get to grips with studying proteins, not just genes. Reliable methods for the overexpression of proteins in their native state coupled with routine access to structure determination must become the norm rather than the exception. In 1998 there were about 9000 protein structures deposited in the Brookhaven database. Very few of these are plant proteins. This trend will have to be reversed if research in molecular plant science is to fulfil its potential.

contents

Summary
167

I.
introduction
168

II.
the impact of protein structural information on the understanding of the primary reactions in photosynthesis
169

III.
developing overexpression systems for the study of plant protein
188

IV.
conclusions
190
Fumigation with exogenous monoterpenes of a non‐isoprenoid‐emitting oak (Quercus suber): monoterpene acquisition, translocation, and effect on the photosynthetic properties at high temperatures
Authors: DELFINE SEBASTIANO , CSIKY OLAV , SEUFERT GUENTHER , LORETO FRANCESCO
Published: March 2003

We tested if fumigation with exogenous monoterpenes might induce thermotolerance in leaves of an oak species (Quercus suber) which does not form and emit isoprenoids. To understand if exogenous monoterpene fumigation results in internal accumulation of monoterpenes, a physical method of monoterpene extraction was used. The internal content of monoterpenes increased in concert with increasing fumigation doses. This unambiguously demonstrated acquisition of exogenous monoterpenes. We exposed fumigated Q. suber leaves to two cycles of increasing temperatures from 35 to 55°C at 5°C steps. When leaves were exposed to a low dose of exogenous monoterpenes, yielding an internal content similar to that endogenously formed in the leaves of the monoterpene‐emitter Q. ilex, no clear improvement in thermotolerance was found. When leaves were exposed to a high dose of exogenous monoterpenes, yielding an internal content of about five fold the endogenous pool of Q. ilex, but comparable with the expected content following stress‐induced stomatal closure, photosynthesis inhibition at high temperatures was attenuated. This effect was observed only at temperatures <45°C during the first cycle, but at all temperatures between 35 and 55°C when plants were exposed to two cycles of high temperatures. Monoterpenes were still found in the leaves of Q. suber 12 h after ending the fumigation. Monoterpenes were also found in non‐fumigated leaves distant up to 45 cm from the fumigated leaves. If monoterpenes make the photosynthetic apparatus more resistant to high temperatures, the effect might not be limited to the fumigated leaves and might be persistent after fumigation.
Elevated atmospheric CO2, fine roots and the response of soil microorganisms: a review and hypothesis
Authors: ZAK DONALD R. , PREGITZER KURT S. , KING JOHN S. , HOLMES WILLIAM E.
Published: March 2003

There is considerable uncertainty about how rates of soil carbon (C) and nitrogen (N) cycling will change as CO2
accumulates in the Earth's atmosphere. We summarized data from 47 published reports on soil C and N cycling
under elevated CO2 in an attempt to generalize whether rates will increase, decrease, or not change. Our synthesis
centres on changes in soil respiration, microbial respiration, microbial biomass, gross N mineralization, microbial
immobilization and net N mineralization, because these pools and processes represent important control points for
the below‐ground flow of C and N. To determine whether differences in C allocation between plant life forms
influence soil C and N cycling in a predictable manner, we summarized responses beneath graminoid, herbaceous
and woody plants grown under ambient and elevated atmospheric CO2. The below‐ground pools and processes
that we summarized are characterized by a high degree of variability (coefficient of variation 80–800%), making
generalizations within and between plant life forms difficult. With few exceptions, rates of soil and microbial
respiration were more rapid under elevated CO2, indicating that (1) greater plant growth under elevated CO2
enhanced the amount of C entering the soil, and (2) additional substrate was being metabolized by soil
microorganisms. However, microbial biomass, gross N mineralization, microbial immobilization and net N
mineralization are characterized by large increases and declines under elevated CO2, contributing to a high degree
of variability within and between plant life forms. From this analysis we conclude that there are insufficient data
to predict how microbial activity and rates of soil C and N cycling will change as the atmospheric CO2
concentration continues to rise. We argue that current gaps in our understanding of fine‐root biology limit our
ability to predict the response of soil microorganisms to rising atmospheric CO2, and that understanding
differences in fine‐root longevity and biochemistry between plant species are necessary for developing a predictive
model of soil C and N cycling under elevated CO2.
Comparative anatomy of ectomycorrhizas synthesized on Douglas fir by Rhizopogon spp. and the hypogeous relative Truncocolumella citrina
Authors: MASSICOTTE HUGUES B. , MELVILLE LEWIS H. , PETERSON R. LARRY , MOLINA RANDY
Published: March 2003

The morphology and anatomy of ectomycorrhizas of Rhizopogon parksii, Rhizopogon vinicolor and
Rhizopogon subcaerulescens, and a hypogeous relative, Truncocolumella citrina, synthesized on Douglas fir in glasshouse
conditions using spore slurries as inoculum, are described and compared. Mycorrhizas formed with R. parksii and
R. vinicolor did not exhibit their characteristic subtuberculate morphology in these tests, but rather had a pinnate
form. All species had diagnostic features of ectomycorrhizas: a well‐developed Hartig net and a fungal mantle. In
addition, several species exhibited crystal inclusions in the outer mantle, usually at the interface between the
mantle and soil. Truncocolumella citrina had crystal‐like inclusions within the mantle but external to fungal hyphae, a feature rarely described in ectomycorrhizas.
Tansley Review No. 118
Authors: KINGSTON‐SMITH A. H. , THEODOROU M. K.
Published: March 2003

It is generally assumed that breakdown of plant material in the rumen is a process mediated by gut microorganisms. This view arose because of the identification of a pre‐gastric fermentation in the rumen, brought about by a large and diverse microbial population. The extensive use of dried and ground feed particles in forage evaluation might have helped to promote this assumption. However, although the assumption might be correct in animals feeding on conserved forage (hay and silage) where the cells of ingested forage are dead, it is possible that with grazed (living) forage, the role played by plant enzymes in the rumen has been overlooked. In a grazing situation, plant cells that remain intact on entering the rumen are not inert, but will respond to the perceived stresses of the rumen environment for as long as they are metabolically viable. Metabolic adjustments could include anaerobic and heat‐shock responses that could promote premature senescence, leading to remobilization of cell components, especially proteins. Moreover, contact of plant cells with colonizing microorganisms in the rumen might promote a type of hypersensitive response, in much the same way as it does outside the rumen. After fresh plant material enters the rumen and prior to extensive plant cell‐wall degradation, there is often a phase of rapid proteolysis providing N in excess of that required to maintain the rumen microbial population. The inefficient use of this ingested N results in generation of ammonia and urea in exhaled breath and urine, which promotes welfare and environmental pollution concerns. Therefore an important research goal in livestock agriculture is to find ways of decreasing this initial rate of proteolysis in the rumen. This will benefit the farmer financially (through decreased use of feed supplements), but will also benefit the environment, as N pollution can adversely affect pasture diversity and ecology. This review considers the possible responses of plant metabolism to the rumen environment, and how such considerations could alter current thinking in ruminant agriculture.

Contents

Summary
37

I.
INTRODUCTION
37

II.
DIGESTION OF PLANTS IN THE RUMEN: OLD AND NEW CONCEPTS
39

III.
RUMEN‐INDUCED PLANT METABOLISM: CELL DEGRADATION AND DEATH
41

IV.
FUTURE PROSPECTS
50

Acknowledgements
51

References
51
Why do basic research? A lesson from commercial exploitation of miscanthus
Authors: Jørgensen U. , Schwarz K.‐U.
Published: March 2003

Extended areas of new crops to produce not only food, but also energy and materials, was one of the visions when the EU agricultural policy was reformed in 1992. However, this vision remains unfulfilled. The perennial C4 grass
Miscanthus, originating from eastern Asia, was one of the
crops that caught major interest as a potential biomass
crop due to its high productivity even in cool northern
European conditions (Beale & Long, 1995). However,
even very large initial programmes on Miscanthus were
conducted almost exclusively within one genotype, namely
the sterile, triploid, interspecific hybrid M. ×giganteus,
and ran into significant problems of low first winter
survival and prohibitive high costs of vegetative establishment. Thus, despite the many encouraging results on
Miscanthus productivity (van der Werf et al., 1993),
environmental acceptability (Christian & Riche, 1998) and
harvest and storage suitability (Venturi et al., 1998), it is
clear that the introduction of a new crop into agriculture is
not simple, and that basic ecophysiological understanding
is important to support commercial exploitation. The
results in this issue from Clifton‐Brown & Lewandowski
(see pp. 287–294) contribute to this vital, basic understanding,
revealing that low frost tolerance of M. ×giganteus rhizomes is probably the cause of low winter
survival in cool parts of Europe, but that within the genus
Miscanthus better frost tolerance exists.
Ontogeny modifies the effects of water stress on stomatal control, leaf area duration and biomass partitioning of Pennisetum glaucum
Authors: Winkel T. , Payne W. , Renno J.‐F.
Published: March 2003

• Experiments are presented that test the relative importance, during ontogeny, of stomatal control and leaf area expansion to optimum seasonal water use in pearl millet (Pennisetum glaucum). These parameters play a key role in the compromise between plant growth and water saving under unpredictable conditions of semiarid environments.

• The response of growth and water use of crops to successive 15 d drought periods was measured under field conditions in Niger (West Africa).

• From emergence to anthesis, biomass partitioning to stems and panicles depended strongly on leaf area development. Water use was linearly related to green leaf area duration in well watered plots, but was reduced proportionally more than green leaf area in drought‐affected plots. The relations of crop growth rate and transpiration efficiency to leaf area depended on ontogenetic changes in biomass partitioning.

• In P. glaucum, stomata play a dominant role in reducing crop water use under preanthesis drought, although this control becomes negligible after anthesis because of ontogenetic decline in the range of stomatal conductance. The rate of leaf senescence after anthesis is not drought‐dependent.
Genetic variability of Pisolithus isolates associated with native hosts and exotic eucalyptus in the western Mediterranean region
Authors: Díez Jesús , Anta Berta , Manjón José Luis , Honrubia Mario
Published: March 2003

• Genetic diversity and host specificity of Pisolithus is reported here in exotic (Eucalyptus) and native hosts in the western Mediterranean region.

• Polymorphism in the internal transcribed spacer (ITS) sequences of the nuclear rDNA of Pisolithus was analysed. Sequences for 17 isolates associated with native Mediterranean hosts and Eucalyptus were compared with those in the GenBank DNA database using distance and parsimony methods.

• Bootstrap analysis showed clustering of all Pisolithus isolates associated with Mediterranean hosts. The ITS sequences suggest the occurrence of several ecological species adapted to exploit different soil types (basic, acid and clayey slate‐derived soils), with specificity for particular indigenous hosts. Isolates from eucalypt plantations in Brazil, Kenya and the Mediterranean grouped together with eucalypt‐associated Australian isolates. Transfer to native hosts did not occur; the host specificity range of these exotic strains might prevent out‐competition and interbreeding with local species.

• Pisolithus spp. in eucalypt plantations in the Mediterranean basin are of Australian origin; the co‐introduction of the ectomycorrhizal fungi might explain the success of these exotic forest plantations.
Secondary metabolites and nutrient concentrations in silver birch seedlings under five levels of daily UV‐B exposure and two relative nutrient addition rates
Authors: De La Rosa T. M. , Julkunen‐Tiitto R. , Lehto T. , Aphalo P. J.
Published: March 2003

Changes in secondary metabolites in silver birch ( Betula pendula ) seedlings are presented in response to ultraviolet‐B radiation (UV‐B) and nutrient addition.

Concentrations of individual secondary metabolites and nutrients were measured in leaves of greenhouse‐grown silver birch seedlings exposed to five time‐integrated irradiances of biologically effective UV‐B (I BE
UV‐B ) and fertilized with two relative nutrient addition rates.

Several phenolics were not only induced by UV‐B, but their concentration was dependent on UV‐B daily time‐integrated irradiance. Relative nutrient addition rate also affected the concentration of phenolics but had little effect on the UV‐B daily time‐integrated irradiance‐responses. The mineral nutrient concentration of leaves was affected by nutrient addition but not by increasing I BE
UV‐B . Possible threshold‐exposures for the accumulation of secondary metabolites or nutrients were not detected.

UV‐B and relative nutrient addition rate have mainly an additive (rather than synergistic) effect in silver birch, and leaves respond to increasing UV‐B by synthesizing metabolites (e.g. flavonols), which are important UV‐B filters. This study reports the first UV‐B‐exposure‐response curves for individual secondary metabolites and nutrients in leaves of a woody tree species.
Can unidirectional influx be measured in higher plants? A mathematical approach using parameters from efflux analysis
Authors: Britto Dev T. , Kronzucker Herbert J.
Published: March 2003

A comprehensive and pragmatic approach to the design of unidirectional ion transport experiments in plants is presented here, revising and simplifying classical models.

The kinetic constant for cytosolic ion exchange ( k
c ) is critical to the understanding of the interrelated flux processes occurring simultaneously at the cellular level. This constant is most effectively estimated using the compartmental analysis by efflux method, which, by providing values for additional kinetic parameters (i.e. unidirectional influx and efflux) can be used to determine the extent of distortion inherent in assessments of influx at, or close to, the steady state.

Focusing on the kinetics of nitrogen exchange, with tracer efflux experiments in barley ( Hordeum vulgare
) using
13NH4+, conducted under perturbation conditions, it was demonstrated that a transitional state was rapidly established following a concentration shift, characterized by a restoration of the preperturbational (steady‐state) kc value. It is concluded that a reasonably accurate estimate of unidirectional influx can be made when influx measurements are conducted subsequent to the establishment of this transitional state.

A mathematical treatment of unidirectional flux processes allows the exact determination of errors caused by ionic counterfluxes under steady‐state conditions.
Soil‐borne fungal pathogens: scaling‐up from hyphal to colony behaviour and the probability of disease transmission
Authors: Stacey A. J. , Truscott J. E. , Gilligan C. A.
Published: March 2003

The transmission of many fungal soil‐borne plant pathogens is mediated by the growth of the fungal colony from an infectious to a susceptible host plant.

Here we develop a mechanistic, spatially‐explicit, mathematical model that allows us to scale from hyphal growth and branching, through colony growth to analyse and predict the transmission of infection. We derive approximate analytical solutions for colony behaviour. These are used to drive equations for the evolution of the pathozone dynamics which characterize the ability of pathogens to infect hosts from various distances in soil.

It is possible to scale up from hyphal behaviour to the scale of transmission of infection. We identify two key periods in pathozone dynamics: an initial period during which no transmission of infection occurs, followed by the advection of the pathozone profile away from the infectious host at an approximately constant rate.

The models enable the prediction of probability of transmission of infection from hyphal‐scale behaviour. However, a coherent theory scaling from hyphal dynamics through colony behaviour to properties of the whole epidemic awaits further theoretical and experimental work.
Analysis of gene expression in arbuscular mycorrhizas: new approaches and challenges
Authors: Franken P. , Requena N.
Published: March 2003

This review summarizes the most recent results obtained using molecular biological techniques in the understanding of the arbuscular mycorrhizal symbiosis. On the plant side, cDNA libraries have been established from mycorrhizal RNA using several techniques, such as suppressive subtractive hybridization, and a large number of clones are being sequenced to obtain expressed sequence tags (ESTs). These ESTs can be transferred to solid supports (arrays) and hybridized with cDNA from different sources to obtain RNA accumulation profiles of genes expressed during the mycorrhizal symbiosis. On the fungal side, EST libraries are also being established, both using direct cloning and suppressive subtractive hybridization techniques. For both partners, the next steps are the detailed analysis of some relevant genes concerned with regulation and function, as well as the study of their role in the symbiosis. At the end of this review, we discuss how results about gene expression and functioning from molecular analyses can help in understanding the ecology of the symbiosis and the way in which it can be further exploited for application in plant production systems.
Stem respiration increases in CO2‐enriched sweetgum trees
Authors: Edwards Nelson T. , Tschaplinski Timothy J. , Norby Richard J.
Published: March 2003

Stem respiration in trees results in substantial CO 2
release to the atmosphere. Stem respiration is an important component of the carbon budget of forest stands that could be perturbed by CO
2 enrichment of the atmosphere.

We measured stem respiration in a free‐air CO 2
enrichment (FACE) experiment in a 15‐yr‐old sweetgum (
Liquidambar styraciflua
) plantation. The trees were exposed to ambient or 1.4× ambient [CO
2
]. Stem respiration of 12 trees in ambient [CO
2
] and 12 trees in CO
2 ‐enriched plots was continuously monitored over a period of 1 year.

CO2 enrichment caused a 23% increase in annual growth respiration (Rg) and a 48% increase in maintenance respiration (Rm). During a 4‐d period when CO2 fumigation was turned off, both respiration and stem sucrose concentrations declined in the CO2‐enriched trees. Concentrations of other soluble sugars did not change.

We conclude that elevated [CO 2
] caused stem respiration to increase and that the increase was driven by increased substrate supply from leaves. We suggest that both
R
g
and
R
m rate responses may result from changes in growth rates and live to dead tissue ratios rather than from mechanistic alterations of the respiratory processes.
Anthocyanins in vegetative tissues: a proposed unified function in photoprotection
Authors: Steyn W. J. , Wand S. J. E. , Holcroft D. M. , Jacobs G.
Published: March 2003

The function of anthocyanins in green, vegetative tissues has always been a contentious issue. Here we evaluate their proposed photoprotective function since recent findings have shown that anthocyanins reduce photoinhibition and photobleaching of chlorophyll under light stress conditions. Anthocyanins generally accumulate in peripheral tissues exposed to high irradiance, although there are some exceptions (e.g. accumulation in abaxial leaf tissues and in obligatory shade plants) and accumulation is usually transient. Anthocyanin accumulation requires light and generally coincides with periods of high excitation pressure and increased potential for photo‐oxidative damage due to an imbalance between light capture, CO2 assimilation and carbohydrate utilization (e.g. greening of developing tissues, senescence and adverse environmental conditions). Light attenuation by anthocyanin may help to re‐establish this balance and so reduce the risk of photo‐oxidative damage. Although it has been suggested that anthocyanins may act as antioxidants, the association between anthocyanins and oxidative stress appears to relate to the ability of anthocyanins to reduce excitation pressure and, hence, the potential for oxidative damage. The various aspects of anthocyanin induction and pigmentation presented here are compatible with, and support, the proposed general role of anthocyanins as photoprotective light screens in vegetative tissues.
Consumers’ views of breast care services in Ireland
Authors: Kennedy P. , Murphy‐Lawless J. , Quin S. , Hickey E.
Published: March 2003

One Irish woman in 14 develops breast cancer. There are 1700 new cases each year. These rates compare poorly with EU figures. The government indicated in 1995 that it favoured rapid, comprehensive diagnostic facilities, using the triple assessment model of clinical care, to improve survival rates and to diminish the anxiety women experience about breast cancer. Implementation of this policy was delayed until 1999, when a plan for centres of excellence in breast care was conceived. To compliment this plan, the Department of Health and Children wanted consumer views on existing breast care services. The Women’s Health Council was asked by the Department of Health and Children, through the National Cancer Forum, to conduct research on women’s views and reactions as consumers of existing services for symptomatic breast disease. The research team was asked to document women’s views on: diagnostic services; counselling; additional treatment services such as surgery and radiotherapy. The methodology consisted of four strands: questionnaires and focus groups with consumers of breast care services; postal questionnaires to clinic staff and a literature review. Striking aspects were the long delays women experienced before obtaining a completed diagnosis; often chaotic clinic settings which added greatly to women’s shock and anxiety; the lack of support if they received a diagnosis of cancer; and problems relating to limited resources for cancer treatment, including radiotherapy. We explored women’s coping mechanisms and their experiences, in the context of the model of quality of care. Finally, we argue that a centre of excellence must develop a multidimensional model of breast disease care that incorporates the full range of psycho‐social dimensions for women, if it is to earn its claim to excellence.
Reduced‐fat foods: the shopper’s viewpoint
Authors: Hill D. S. , Knox B. , Hamilton J. , Parr H. , Stringer M.
Published: March 2003

The inclusion of reduced‐fat foods in the daily diet affords consumers the potential to reduce overall dietary fat. Nevertheless, despite an increased range of these food products throughout the market, there has remained a lack of widespread consumer acceptance. The aim of the study was therefore to understand why consumers choose or reject reduced‐fat foods. Ninety consumers were interviewed by means of a qualitative approach within food retail outlets in the United Kingdom. Thematic content analysis indicated that uptake or rejection of these products is influenced by health concerns, ‘goodness of fit’ with individual dietary health strategies, the preferences of different household members, perceived sensory properties and scepticism towards these products. The results imply a need to explore and innovate ‘natural’ fat substitutes and to improve the sensory quality of reduced‐fat products. Further research is required to determine how these foods are used within the household and incorporated within the overall diet. Policy must seek to restore consumer trust in reduced‐fat food products and the food supply generally.
The effects of the US Food Stamp Program on the dietary quality of parents and their teenagers and children1
Authors: Sapp Stephen G.
Published: March 2003

Although previous research finds that participation in Food Stamp Programs increases the nutrient availability of low‐income households, examination of the dietary quality of parents, their teenagers (aged 13–18 years), and their children (aged 1–12 years) indicates that participation has no effect on dietary quality of any of these groups. Examination of data from the Continuing Survey of Food Intake by Individuals and Diet and Health Surveys, conducted in the USA, 1994–96, indicates that although transfer payments in the Food Stamp Program might improve quality of life in other areas by freeing income otherwise spent on food, the receipt of food assistance does not improve dietary quality. The findings show that children tend to eat healthier diets than their parents or teenage siblings. Implications are suggested regarding the use of transfer payments to improve the dietary quality of persons living in poverty.
Consumer complaints and redress: an important mechanism for protecting and empowering consumers1
Authors: Hogarth Jeanne M. , English Maureen P.
Published: March 2003

This paper explores a consumer complaint programme as a tool for empowering consumers, using the consumer complaint programme of a United States federal agency as a case study. After describing the structure and role of the Federal Reserve System (the central bank of the United States) in handling complaints, the paper follows a complaint through the System, looks at trends in complaints and provides a profile of consumers who complain. The paper concludes with information on the economic impact of complaint resolution and consumer satisfaction with third‐party complaint investigation.
Food, exercise and lifestyle: an initial teacher training perspective
Authors: Lakin Liz
Published: March 2003

All too often, we are told via the media that our children are overweight, under‐exercised and eating poor diets. This is disconcerting at the best of times but even more so when we, as a country, are reviewing our farming and food production practices. So what is our perception of food and how does this relate to the lives we lead? These questions were put to initial teacher‐trainees (ITT) at the University of Gloucestershire. They will be the teachers of tomorrow, playing a significant role in the development and lifestyles of our children. The answers received were varied; both encouraging and giving cause for concern. This paper describes an action research project based around the analysis of those answers in the light of current research into food and health. Throughout the paper, published research findings relating to school children's perception of food and nutrition are compared with the trainee teachers’ views. The comparison draws striking similarities. The implications of this point to the way we teach food and nutrition in schools and on our ITT programme at the University of Gloucestershire. Whilst praising the good practice that already exists, this paper recognises that there is a need to adequately equip trainee teachers, especially at primary level, to educate children towards a more holistic understanding of the food we eat and how it relates to the lifestyles we lead.
Consumer skills for all: a research study carried out for the General Consumer Council for Northern Ireland
Authors: Edwards Carol
Published: March 2003

The General Consumer Council for Northern Ireland (GCCNI) is one of the four Consumer Councils operating within the United Kingdom (the others are the Welsh, the Scottish and the National Consumer Council, which covers England and links with the other Consumer Councils). The GCCNI has a long standing interest in consumer education, and has produced a quantity of well‐regarded consumer education material aimed at both schools and adults over recent years. It has also organised regular consumer education events for schools and conferences on this subject., However, the GCCNI is aware that many people in Northern Ireland suffer difficulties in relation to consumer issues and is looking for a clear policy on dealing with those difficulties. They contracted researchers at Queen's University, Belfast to investigate the extent of the problem, with the aim of identifying the key aspects of a new consumer education and skills development strategy and the gaps and deficiencies in current provision that need to be addressed. While the GCCNI acknowledges that these problems are not exclusive to Northern Ireland, and that the nature of the problems is relatively well‐known, they felt that conditions in Northern Ireland were unique and deserving of a specific and targeted solution. Policy and decision makers in other countries will find the Northern Ireland experience of interest, both from the way in which the problem was approached and the solution which evolved.