bluuebunny/crossref_metadata_2025 huggingface dataset:
Toxicity of arsenate in Silene vulgaris, accumulation and degradation of arsenate‐induced phytochelatins
Authors: SNELLER F. E. C. , VAN HEERWAARDEN L. M. , KRAAIJEVELD‐SMIT F. J. L. , TEN BOOKUM W. M. , KOEVOETS P. L. M. , SCHAT H. , VERKLEIJ J. A. C.
Published: March 2003

The results presented in this paper describe the short‐ and long‐term toxicity of arsenate in Silene vulgaris. Short‐term toxicity, measured as inhibition of root elongation, depended on phosphate nutrition, arsenate being much less toxic at high phosphate supply. At low phosphate levels more arsenic was taken up by the plants. Under chronic exposure, toxicity (measured as inhibition of biomass production) did not increase with time. In addition, the accumulation of phytochelatins (PCs) as a function of toxicity and duration of exposure was studied. Short‐term PC accumulation (over a 3 d period) was positively correlated with exposure. Isolation of peptide complexes from prolongedly exposed plants showed that PC2, PC3 and PC4 were present, although the latter not until at least 3 d exposure. Arsenic co‐eluted mainly with PC2 and PC3. Fractions containing PC4 were devoid of As, probably due to dissociation of the complexes during extraction or elution. The breakdown of PCs after arresting As exposure was very slow. This could explain the continuous accumulation of PCs throughout longer periods of As exposure.
Isolation and characterization of a general amino acid permease from the ectomycorrhizal fungus Amanita muscaria
Authors: NEHLS UWE , KLEBER REGINE , WIESE JOACHIM , HAMPP RÜDIGER
Published: March 2003

A cDNA coding for a fungal amino acid transporter (AmAAP1) was identified from Amanita muscaria ectomycorrhizas. The transporter gene was expressed at a basal level under all conditions investigated, but its expression was enhanced 10‐fold in the absence of a N source utilized by the fungus. Nitrate was not a suitable N source for A. muscaria and resulted in maximal AmAAP1 expression. The expression of AmAAP1 in a yeast mutant revealed its function as a high‐affinity amino acid transporter with a broad substrate spectrum. AmAAP1 takes up all investigated amino acids with Km values between 22 μM for histidine and up to 100 μM for proline. Gene expression and amino acid uptake data together indicate two main functions for AmAAP1: uptake of amino acids from soil for fungal nutrition, and prevention of an amino acid loss by hyphal leakage in the absence of a suitable N source.
Common anastomosis and internal transcribed spacer RFLP groupings in binucleate Rhizoctonia isolates representing root endophytes of Pinus sylvestris, Ceratorhiza spp. from orchid mycorrhizas and a phytopathogenic anastomosis group
Authors: SEN ROBIN , HIETALA ARI M. , ZELMER CARLA D.
Published: March 2003

Binucleate Rhizoctonia endophytes from the roots of nursery‐grown Pinus sylvestris (Scots pine) seedlings and the orchid Goodyera repens from Scots pine forests were characterized on the basis of morphological characters, anastomosis group membership and PCR‐assisted ribosomal DNA fingerprinting. Common hyphal and colony morphological traits displayed by the Finnish binucleate Rhizoctonia isolates and a range of Canadian orchid root endophytes enabled them to be placed in the anamorphic genus Ceratorhiza. Five main anastomosis groups were identified and included groups that contained different combinations of Scots pine, G. repens and Canadian Ceratorhiza spp. isolates. Two Scots pine root endophytes anastomosed with a phytopathogenic Japanese tester isolate, confirming their membership of anastomosis group I, which is known to include the teleomorphic species Ceratobasidium cornigerum. Hierarchical cluster analysis of RFLPs in the internal transcribed spacer of ribosomal DNA enabled the division of isolates into one of five RFLP groups. The RFLP and anastomosis groupings were closely correlated; isolates within each of four RFLP groups, which shared 100% RFLP identity, anastomosed in the cross‐pairing anastomosis group tests. However, all represented different vegetatively compatible populations (clones) because the diagnostic killing reaction, a cellular vegetative incompatibility response, was identified at hyphal fusion junctions. These findings indicate a high degree of intraspecific variation within Ceratobasidium cornigerum, which includes isolates able to enter into either mutualistic or pathogenic root association with susceptible host plants. The common anastomosis group/RFLP groupings identified also strongly support the hypothesis that conifer tree roots can act as large inoculum reservoirs for these orchid endophytes, allowing the development of inter‐plant connections, via commonly shared hyphal linkages, in boreal forest ecosystems.
Responses of two provenances of Fagus sylvatica seedlings to a combination of four temperature and two CO2 treatments during their first growing season: gas exchange of leaves and roots
Authors: LEVERENZ J. W. , BRUHN D. , SAXE H.
Published: March 2003

Physiological responses of two provenances of European beech (Fagus sylvatica) were studied in seedlings grown at two [CO2] in combination with four temperature treatments. For the local Danish provenance, the average effect of elevated [CO2] during growth was to increase light‐saturated net photosynthesis (An) and instantaneous water‐use efficiency or transpiration efficiency (ITE). These increases were strongly related to the temperature treatment. Stomatal conductance (gs) was reduced in seedlings in high [CO2], but there was no statistically significant effect of temperature treatment. Stomatal conductance was 13–26% lower at elevated [CO2] and ITE was 89–156% higher, depending on growth temperature. The effects of [CO2] on An were considerably larger than those shown for many other woody species, but similar to those in other studies on European beech. The absolute value of An for a Romanian provenance of beech was 5–18% lower than in the Danish provenance at low [CO2] and 14–26% lower at high [CO2]. There was no statistically significant interaction between the provenances and [CO2], or between provenance and temperature. A model of the response of An to [CO2] at different temperatures gave predictions close to the measured results, except at the lowest temperature treatment where the model over‐predicted the effect of elevated [CO2]. This and measurements of An made at a common, low [CO2] indicated a down‐regulation of photosynthesis in the lowest temperature treatment at high [CO2]. Root plus soil respiration on a whole‐tree basis (Rtr) was increased by elevated [CO2] at all but the lowest temperature, but no effect was seen of [CO2] on root respiration per unit root d. wt. Mean Rtr on any given date was significantly correlated with An, except at the lowest temperature treatment. It is hypothesized that low temperature limited the ability of the roots to use photosynthates resulting in a feedback inhibition of An when elevated [CO2] was combined with low temperature.
Root growth and function of three Mojave Desert grasses in response to elevated atmospheric CO2 concentration
Authors: YODER C. K. , VIVIN P. , DEFALCO L. A. , SEEMANN J. R. , NOWAK R. S.
Published: March 2003

Root growth and physiological responses to elevated CO2 were investigated for three important Mojave Desert grasses: the C3 perennial Achnatherum hymenoides, the C4 perennial Pleuraphis rigida and the C3 annual Bromus madritensis ssp. rubens. Seeds of each species were grown at ambient (360 μl l−1) or elevated (1000 μl l−1) CO2 in a glasshouse and harvested at three phenological stages: vegetative, anthesis and seed fill. Because P. rigida did not flower during the course of this study, harvests for this species represent three vegetative stages. Primary productivity was increased in both C3 grasses in response to elevated CO2 (40 and 19% for A. hymenoides and B. rubens, respectively), but root biomass increased only in the C3 perennial grass. Neither above‐ground nor below‐ground biomass of the C4 perennial grass was significantly affected by the CO2 treatment. Elevated CO2 did not significantly affect root surface area for any species. Total plant nitrogen was also not statistically different between CO2 treatments for any species, indicating no enhanced uptake of N under elevated CO2. Physiological uptake capacities for NO3 and NH4 were not affected by the CO2 treatment during the second harvest; measurements were not made for the first harvest. However, at the third harvest uptake capacity was significantly decreased in response to elevated CO2 for at least one N form in each species. NO3 uptake rates were lower in A. hymenoides and P. rigida, and NH4 uptake rates were lower in B. rubens at elevated CO2. Nitrogen uptake on a whole root‐system basis (NO3+NH4 uptake capacity × root biomass) was influenced positively by elevated CO2 only for A. hymenoides after anthesis. These results suggest that elevated CO2 may result in a competitive advantage for A. hymenoides relative to species that do not increase root‐system N uptake capacity. Root respiration measurements normalized to 20 °C were not significantly affected by the CO2 treatment. However, specific root respiration was significantly correlated with either root C∶N ratio or root water content when all data per species were included within a simple regression model. The results of this study provide little evidence for up‐regulation of root physiology in response to elevated CO2 and indicate that root biomass responses to CO2 are species‐specific.
Symbiotic germination and development of myco‐heterotrophic plants in nature: transfer of carbon from ectomycorrhizal Salix repens and Betula pendula to the orchid Corallorhiza trifida through shared hyphal connections
Authors: McKENDRICK S. L. , LEAKE J. R. , READ D. J.
Published: March 2003

Seedlings of the myco‐heterotrophic orchid Corallorhiza trifida which had been germinated in the field in mesh
bags developed hyphal links and mycorrhizas with Betula pendula and Salix repens, but not with Pinus sylvestris,
when transplanted into soil microcosms. The fungus connecting the myco‐heterotroph to Betula and Salix formed
endomycorrhiza in the orchid with typical pelotons, but formed ectomycorrhizas with the autotrophs. The orchid
plants, when linked to Betula and Salix by fungal hyphae, gained 6–14% in weight over 25–28 wk. In microcosms
supporting P. sylvestris, and in control microcosms which lacked autotrophs, the Corallorhiza plants lost 13% of
their weight over the same period. In the course of the 28‐wk experimental period new Corallorhiza seedlings, in
addition to those added as part of the experiment, appeared in the microcosms containing Salix and Betula but
not in the Pinus microcosms. Shoots of Betula and Salix plants grown in association with Corallorhiza were fed
with 14CO2, and the movement of the isotope was subsequently traced by a combination of digital autoradiography
and tissue oxidation. Direct transfer of C from both autotrophs to the myco‐heterotroph occurred in all cases
where the associates had become connected by a shared fungal symbiont. Orchid seedlings lacking these hyphal
connections, introduced to the microcosms as controls immediately before isotope feeding, failed to assimilate
significant amounts of C. The results provide the first experimental confirmation that growth of Corallorhiza
trifida can be sustained by supply of C received directly from an autotrophic partner through linked fungal mycelia.
Root responses to cereal cyst nematode (Heterodera avenae) in hosts with different resistance genes
Authors: SEAH S. , MILLER C. , SIVASITHAMPARAM K. , LAGUDAH E. S.
Published: March 2003

The development of cereal cyst nematode (CCN; Heterodera avenae) induced syncytia in the host roots of infected
resistant bread wheat (Triticum aestivum cv. AUS10894), diploid wheat (Aegilops tauschii), barley (Hordeum
vulgare cv. Chebec and cv. Galleon) and in the susceptible wheat cv. Meering and barley cv. Clipper were studied
over a period of 13 d. The resistance to CCN in these cereal plants is conferred by the resistance genes Cre1 in
the wheat cv. AUS10894, Cre3 in A. tauschii, Ha2 in barley cv. Chebec and Ha4 in barley cv. Galleon. Anatomical
observations were made on the development of the syncytia in CCN‐infected wheat and barley roots, which carry
each of these four sources of resistance genes. Accelerated development of the syncytia in resistant plants,
especially in the barley cultivars, was observed. The sites of syncytia development in susceptible wheat and barley
were also closely associated with the vascular tissues in the stele, but less so in the resistant plants. The syncytia
in the infected susceptible wheat and barley were also metabolically active at day 13. By contrast, the syncytia of
resistant wheat plants carrying the Cre1 or Cre3 genes remained extensively vacuolated and less metabolically
active. In barley plants with the Ha2 or Ha4 genes, the syncytia appeared non‐functional and in early stages of degeneration by day 13 after inoculation.
Hyphal growth and colony expansion
Authors: van Bruggen A. H. C. , Termorshuizen A. J. , Semenov A. M.
Published: March 2003

Several generations of soil microbiologists and plant pathologists have attempted to unravel the microbial composition, population dynamics and various life‐sustaining processes in the soil. However, until recently, this basic resource for plant growth and nutrient recycling has to a large extent remained a black box. Studies have been made of the behavior of individual microorganisms or their population dynamics, but the relationship between the growth of individual organisms or parts of organisms (such as fungal hyphae) and that of populations and communities has been largely unknown. In particular, the spread of fungal colonies in soil has been an enigma, but now Bailey et al. (pp. 000–000 in this issue) have clearly
demonstrated that spatial behavior of Rhizoctonia colonies can switch from finite to invasive expansion dependent on the non‐linear relationship between the distance among substrate particles and the probability of colonization.
Spatial and temporal deployment of crop roots in CO2‐enriched environments
Authors: PRITCHARD SETH G. , ROGERS HUGO H.
Published: March 2003

Growth of crops in CO2‐enriched atmospheres typically results in significant changes in root growth and
development. Increased root carbohydrates stimulate root growth either directly (functioning as substrates) or
indirectly (functioning as signal molecules) by enhancing cell division or cell expansion, or both. Although highly
variable, the literature suggests that, generally, initiation and stimulation of lateral roots is favored over the
elongation of primary roots, leading to more highly branched, shallower root systems. Such architectural shifts can
render root systems less efficient, perhaps contributing to the lower specific root activities often reported.
Allocation of carbon (C) to roots fluctuates through the life of the plant; root functional and growth responses
should therefore not be viewed as static. In annual crops, C allocation to belowground processes changes as
vegetative growth switches to reproduction and maturation. Reductions in C allocation to roots over time might
cause temporal shifts in root deployment, perhaps affecting root demography. However, significant changes in root
turnover (defined here as root flux or mortality relative to total root pool size) as a result of decreased root
longevities in crop plants are unlikely. Consideration of changing C allocation to roots, a more thorough
understanding of the mechanistic controls on root longevity, and a better characterization of the rooting habits (life
histories) of different crop species will further our understanding of how increasing atmospheric [CO2] will affect root demography. This knowledge will lead the way toward a more thorough understanding of the linkage of atmosphere with belowground plant function and also that of plant function with soil biology and structure. Ultimately, successful modeling of global C and nitrogen (N) cycles will require empirical data concerning spatial and temporal deployment of roots for a range of crop species grown under different agricultural management systems.
Assimilation and metabolism of formaldehyde by leaves appear unlikely to be of value for indoor air purification
Authors: SCHMITZ HERIBERT , HILGERS UTE , WEIDNER MANFRED
Published: March 2003

Uptake, translocation and metabolism of 14C‐labelled formaldehyde in the leaves of Epipremnum aureum (Golden
Potho) and Ficus benjamina (Weeping Fig) were investigated. Plants were exposed in light and dark to 14C‐formaldehyde (500 μg m−3) in gas exposure chambers. The amount of 14C‐incorporation into the soluble (water‐extractable) and insoluble fractions of leaves, stem sections and roots was determined. The soluble 14C‐activity
was fractionated by ion exchange chromatography followed by thin‐layer chromatography/autoradiography.
Approximately 60–70% of the applied 14C‐formaldehyde was recovered from the plants. In the light about five
times more 14C‐formaldehyde was assimilated than in the dark. The amount of 14C‐label derived from 14C‐formaldehyde, which was incorporated into acid‐stable metabolites, was enhanced to an even larger extent in the
light. The 14C‐activity pattern closely resembled the general labelling spectrum of photosynthates, obtained after
a 14CO2 exposure. A substantial amount of labelled material, mostly sucrose, was translocated into the stems and
roots. Our results suggest that in the light 14C enters the Calvin cycle after an enzymatic two‐step oxidation process
of 14C‐formaldehyde to 14CO2. The activities of the respective enzymes, formaldehyde dehydrogenase and formate dehydrogenase, were determined. Among 27 ‘leafy’ indoor decorative plants, a screening experiment revealed no outstanding species with regard to its capacity for metabolism of formaldehyde, and rate of uptake through stomata was too low to justify claims that plants contribute usefully to indoor air purification.
Functional complementarity in the arbuscular mycorrhizal symbiosis
Authors: KOIDE ROGER T.
Published: March 2003

The causes and consequences of biodiversity are central themes in ecology. Perhaps one reason for much of the current interest in biodiversity is the belief that the loss of species (by extinction) or their gain (by invasion) will significantly influence ecosystem function. Arbuscular mycorrhizal (AM) fungi are components of most terrestrial ecosystems and, while many research programs have shown that variability among species or isolates of AM fungi does occur (Giovannetti & Gianinazzi‐Pearson, 1994), the basis for this variability and its consequences to the function of communities and ecosystems remains largely unexplored. Smith et al. (pp. 357–366 in this issue) now show clearly that ecologically significant functional diversity exists among AM fungal species in the regions of the soil from which they absorb phosphate, and their results suggest that such diversity may have significant ecological consequences.
Identification of endophytic fungi from Livistona chinensis based on morphology and rDNA sequences
Authors: GUO L. D. , HYDE K. D. , LIEW E. C. Y.
Published: March 2003

A survey of the endophytic fungi in fronds of Livistona chinensis was carried out in Hong Kong. The endophyte
assemblages identified using morphological characters consisted of 16 named species and 19 ‘morphospecies’, the
latter grouped based on cultural morphology and growth rates. Arrangement of taxa into morphospecies does not
reflect species phylogeny, and therefore selected morphospecies were further identified based on ribosomal DNA
(rDNA) sequence analysis. The 5.8S gene and flanking internal transcribed spacers (ITS1 and ITS2) regions of
rDNA from 19 representative morphospecies were amplified by the polymerase chain reaction and sequenced.
Phylogenetic analysis based on 5.8S gene sequences showed that these morphospecies were filamentous
Ascomycota, belonging in the Loculoascomycetes and Pyrenomycetes. Further identification was conducted by
means of sequence comparison and phylogenetic analysis of both the ITS and 5.8S regions. Results showed that
MS704 belonged to the genus Diaporthe and its anamorph Phomopsis of the Valsaceae. MS594 was inferred to be
Mycosphaerella and its anamorph Cladosporium of the Mycosphaerellaceae. MS339, MS366, MS370, MS395,
MS1033, MS1083 and MS1092 were placed in the genus Xylaria of the Xylariaceae. MS194, MS375 and MS1028 were close to the Clypeosphaeriaceae. MS191 and MS316 were closely related to the Pleosporaceae within the Dothideales. The other 5 morphospecies, MS786, MS1043, MS1065, MS1076 and MS1095, probably belong in the Xylariales. The value of using DNA sequence analysis in the identification of endophytes is discussed.
Symptomless infection of banana and maize by endophytic fungi impairs photosynthetic efficiency
Authors: COSTA PINTO LUCIANA SANTOS RODRIGUES , AZEVEDO JOÃO LÚCIO , PEREIRA JOSÉ ODAIR , CARNEIRO VIEIRA MARIA LÚCIA , LABATE CARLOS ALBERTO
Published: March 2003

Very little is known about the physiological interactions between plant hosts and symptomless endophytic fungi despite their widespread occurrence. We investigated the impact of two such fungi, Colletotrichum musae and
Fusarium moniliforme, upon the photosynthetic capacity of two crop plants, banana and maize, respectively.
Endophyte‐free plants were obtained first and then infected with the fungi. Measurements of total chlorophyll
content revealed very little difference between endophyte‐free and infected plants of banana, whereas in maize they
showed 50% reductions in the endophyte‐infected plants. The maximum photochemical capacity (Fv/Fm ) was
measured in order to determine if the plants had any photoinhibitory effect caused by biotic or abiotic factors.
After 45 d of growth, endophyte‐free banana plants had similar values of Fv/Fm to plants typical of nonstressed
conditions, whereas the endophyte‐infected plants showed a reduction of approx. 15%. Unlike banana, infected
maize plants displayed values of Fv/Fm similar to those of control and endophyte‐free plants, indicating that the
maximum photochemical capacity was not affected by infection. The light response curves of both species showed
that the photosynthethic capacity was severely reduced in endophyte‐infected plants, reaching saturation at c. 400 μmol m−2s−1 whereas the control and endophyte‐free plants were saturated at much higher photon flux densities. In banana the effect seemed to be due to an impairment of electron transport in the thylakoid membranes. By contrast, reduction of the photosynthetic capacity in maize was due to a reduction in chlorophyll content, leading to a decrease in the electron transport components and a consequent reduction in carbohydrate synthesis. It is possible that the reduction in the maximum yield of photosynthesis in both crops was caused by toxins produced by the fungi. Nevertheless there were no major macroscopic effects on the plants to indicate disease symptoms.
Water relations and carbon gain are closely related to cushion size in the moss Grimmia pulvinata
Authors: ZOTZ GERHARD , SCHWEIKERT ANJA , JETZ WALTER , WESTERMAN HERTA
Published: March 2003

The present study of structural and physiological changes during the development of the cushion moss, Grimmia
pulvinata, quantifies the size‐dependence of various parameters of water relations such as changes in
surface: volume ratio (S/V) or water loss rates, and also measures net CO2 gas exchange in the light and the dark.
Larger cushions had lower S/V values than smaller ones and featured lower rates of area‐based evapotranspiration,
owing to higher boundary‐layer resistance, but did not differ in relative water storage capacity (expressed as a
percentage of d. wt). In combination, this leads to considerably longer hydration periods in larger cushions. By
contrast, CO2 gas‐exchange parameters were negatively correlated with size : larger cushions showed significantly lower (mass‐based) rates of net photosynthesis and dark respiration. Using these data, we estimated carbon budgets during a drying cycle as a function of cushion size. When including alternations of dark and light periods, the relationship proved to be rather complicated. Depending on the time of hydration, net carbon budgets not only varied quantitatively with size but sometimes took on both positive and negative values depending on cushion size. We conclude that neglecting plant size can lead to unrepeatable or even misleading results in comparative ecophysiological studies, and therefore urge for adequate attention to be paid to size in these studies.
Differentiation of polyphosphate metabolism between the extra‐ and intraradical hyphae of arbuscular mycorrhizal fungi
Authors: Tatsuhiro Ezawa , Sally E. Smith , F. Andrew Smith
Published: March 2003

• Regulation of polyphosphate metabolism is reported in arbuscular mycorrhizal symbiosis.

• Marigold (Tagetes patula) plants inoculated with Glomus coronatum or Glomus etunicatum were grown in mesh bags. Exopolyphosphatase activity in extra‐ and intraradical hyphae was measured and characterized. The hyphae were stained with Neutral red to show acidic vacuoles in which polyphosphate synthesis might occur.

• Exopolyphosphate activity was differently expressed between the extra‐ and intraradical hyphae, as indicated by different pH optima; high activity was observed at pH 5.0 in the intraradical hyphae of both fungal species. Km values were lower at neutral pH with long‐chain polyphosphate, whereas acidic activity showed lower Km with short‐chain polyphosphate. Both extra‐ and intradical hyphae had acidic vacuoles. Polyphosphate occurred in the hyphae of the high‐P, but not the low‐P treatment. By contrast, exopolyphosphatase activity and vacuolar acidity were relatively constant irrespective of polyphosphate status.

• The fungi have at least two different exopolyphosphatase‐type enzymes which are differently expressed between extra‐ and intraradical hyphae; polyphosphate accumulation might be a dynamic balance between synthesis and hydrolysis.
Photosynthesis might be limited by light, not inorganic carbon availability, in three intertidal Gelidiales species
Authors: Mercado Jesús M. , Xavier Niell F. , Candelaria Gil‐Rodríguez M.
Published: March 2003

• The interaction between incident photon fluence density (PFD) and dissolved inorganic carbon (DIC) availability on photosynthesis is reported for three species of Gelidiales (Rhodophyta) from the Canary Islands.

• Photosynthetic O2 evolution in response to both DIC concentration and PFD, and external carbonic anhydrase activity were measured in thalli of Gelidium canariensis, Gelidium arbuscula and Pterocladiella capillacea maintained in a controlled‐environment room.

• No detectable external carbonic anhydrase activity, high sensitivity to alkaline pH and moderate values of photosynthetic conductance for DIC indicated that the three species had a low capacity for using the external pool of HCO3−; therefore photosynthetic rates were dependent on CO2 availability. The seawater concentration of DIC was insufficient to saturate photosynthesis at high PFD; photosynthesis vs PFD was not affected by DIC concentration at 0.07–0.04 mol O2 mol−1 photon. ANOVA revealed that incident PFD had a greater effect than DIC availability on photosynthesis rates in G. canariensis.

• Photosynthesis is probably limited by incident light rather than DIC concentration despite the apparent low affinity for HCO3− in G. canariensis, G. arbuscula and P. capillacea in their natural habitats.
Light and salinity affect growth of the salt marsh plantAster laurentianus
Authors: Reynolds Christina E. , Houle Gilles , Marquis Christophe
Published: March 2003

• The effects are reported of substrate salinity and light on the relative growth rate of the annualAster laurentianus, an endangered species of eastern Canadian salt marshes.

• The independent and combined effects of photosynthetically active photon flux density and salinity on the relative growth rate (RGR) and overall plant performance were measured in glasshouse and growth‐chamber experiments on seedlings ofA. laurentianus.

•  Low light availability decreased RGR through its negative effect on unit leaf rate. However, specific leaf area and leaf mass ratio varied inversely with changes in light, such that leaf area ratio did not differ greatly among light levels. High salinity decreased RGR by reducing unit leaf rate and leaf area ratio; a reduction in the latter was brought about by a lower leaf mass ratio rather than by a lower specific leaf area. Low light availability combined with high substrate salinity affectedA. laurentianusin a strictly additive manner; there was no significant interaction between the two factors on overall plant performance.

• Light and salinity are important factors controlling growth ofA. laurentianus,and might explain the distribution pattern of the species in the field.
Symbiotic specificity of tropical tree rhizobia for host legumes
Authors: Bala Abdullahi , Giller Ken E.
Published: March 2003

• The host range and specificity is reported of a genetically diverse group of rhizobia isolated from nodules of Calliandra calothyrsus, Gliricidia sepium, Leucaena leucocephala and Sesbania sesban.

• Nodule number and nitrogen content was measured in seedlings of herbaceous and woody legume species after inoculation with rhizobial strains isolated from tropical soils, to establish symbiotic effectiveness groups for rhizobial strains and their hosts.

• Specificity for nodulation and N2 fixation varied greatly among the legumes. Symbionts of all four legumes exhibited a wide range of promiscuity and symbiotic effectiveness with isolates of S. sesban having the narrowest host range. N2 fixation varied greatly; although some strains fixed large amounts of N2 with more than one host, none was effective with all hosts. Rhizobial isolates of C. calothyrsus, G. sepium and L. leucocephala were able to effectively cross‐nodulate each others’ hosts as well as a number of other species.

• The complex nature of cross‐nodulation relationships between diverse rhizobial strains and legume hosts is highlighted. Host plants inoculated with effective rhizobial strains showed better nitrogen use efficiency than plants supplied solely with mineral nitrogen.
Nutrients and pH regulate algicide accumulation in cultures of the cyanobacterium Oscillatoria laetevirens
Authors: Ray S. , Bagchi S. N.
Published: March 2003

• The change in algicide synthesis in response to nutrients and pH in axenic cultures of the planktonic cyanobacterium, Oscillatoria laetevirens is reported.

• Analytical and bioassay techniques were used to determine the effects of nitrogen (N), sulpher (S), phosphorus (P), magnesium (Mg2+), calcium (Ca2+) and hydrogen (H+) on Oscillatoria laetevirens growth, secondary metabolite accumulation and minimum inhibitory concentration in culture filtrates.

• Growth and secondary metabolite production were affected by nutrient addition. High algicide production, which was not dependent on optimal growth, correlated with deficiences of magnesium and phosphate, and high pH. Algicidal activity in the culture medium was not detected following organic nitrogen addition while optimal growth was sustained; however, ammonia reduced biomass yield but did not affect algicide formation. The differential algicide concentration inside the cells and in the culture medium indicated secretion by an efflux mechanism rather than leakage from aging cells.

• Algicide production by Oscillatoria laetevirens was negatively regulated by both phosphate and magnesium, and by pH. The interactive influence of nutrients and allelopathy is discussed in species succession and dominance in the maintenance of freshwater blooms.
Developmental and induced responses of nickel‐based and organic defences of the nickel‐hyperaccumulating shrub, Psychotria douarrei
Authors: Davis Micheal A. , Pritchard Seth G. , Boyd Robert S. , Prior Stephen A.
Published: March 2003

• Developmental and inducible changes in metal‐based (nickel (Ni)) and organic defences (phenolics) are compared in the Ni‐hyperaccumulating shrub, Psychotria douarrei.

• Young and old leaves of P. douarrei shrubs, subjected to different degrees of simulated herbivory, were analyzed for metals, tannins, macronutrients and total carbon, and compared with a co‐occuring nonhyperaccumulator shrub, Ficus webbiana.

• Leaf age affected both nickel Ni‐based and organic defences in P. douarrei; foliar metal concentrations were higher in mature leaves, whereas organic defences were higher in young leaves. Neither metal‐based nor organic defences were increased by simulated herbivore damage, implying noninducibility, although some organic defence compounds were significantly reduced. P. douarrei had a greater percentage of total phenolics, condensed tannins and protein precipitation ability than F. webbianai. Since total carbon content did not differ between species, Psychotria invests more of its leaf carbon budget in organic defences than does Ficus.

• Data suggest that P. douarrei foliage is well protected by Ni, but tannins have multiple functions. The high concentrations of tannins in Psychotria leaves might function as a detoxification mechanism for elevated cytoplasmic metal concentrations, in addition to providing defensive benefits.
Fructans and fructan‐metabolizing enzymes in leaves of Lolium perenne
Authors: Pavis N. , Boucaud J. , Prud’homme M. P.
Published: March 2003

Longitudinal variability is reported in internal carbon partitioning as is the activity of enzymes involved in fructan synthesis during leaf development of Lolium perenne cv. Bravo.

Sink activity was reduced in L. perenne plants by cooling the roots while continuous illumination enhanced source activity, resulting in preferential accumulation of fructans at the leaf base. Fructan contents and enzymatic activity of two trisaccharides (SST (sucrose : sucrose fructosyltransferase) and 6G‐FT (fructan : fructan 6G‐fructosyltransferase)) were measured in segments of elongating leaves, both mature leaf blades and sheaths.

The complement of fructans accumulated was similar in both elongating leaves and mature leaf sheaths. 6G‐FT activity was found in L. perenne and characterized in a crude extract; this activity was greatest in the basal segment of elongating leaves and mature leaf sheaths. Throughout the leaf blade, however, SST and 6G‐FT activities remained low and constant, and did not increase under conditions of sucrose accumulation.

Differences are shown in fructan accumulation between leaf tissues; the significance of these findings and the putative pathway of fructan synthesis in L. perenne are discussed.
Nitrogen fertilization and developmental stage alter the response of Lolium perenne to elevated CO2
Authors: Daepp Markus , Nösberger Josef , Lüscher Andreas
Published: March 2003

Plant response to elevated atmospheric CO2 may depend on the carbon sink strength, determined by the availability of resources other than CO2, and the developmental stage.

 In a 2‐yr field experiment with model swards of Lolium perenne, the effect of CO2 enrichment (FACE) on yield and allocation of dry mass (DM) and N were examined under three N fertilization treatments during vegetative and reproductive growth.

 During vegetative growth, in the highest N treatment, the greatest increase in DM yield occurred at elevated CO2; there was no change in DM allocation. By contrast, at low N, residual biomass, but not yield, increased under CO2 enrichment, and the tillers were shorter. During reproductive growth, under CO2 enrichment DM yield increased similarly across all N treatments; there was no change in DM and N partitioning. The mean weight and height of the reproductive tillers increased.

 At high N availability, or during reproductive growth, L. perenne swards overcome carbon‐sink limitation and show a strong yield response to elevated CO2. Biomass allocation and the height of the plants, in response to elevated CO2, clearly depend on N fertilization and developmental stage.
Unravelling response‐specificity in Ca2+ signalling pathways in plant cells
Authors: Rudd Jason J. , Franklin‐Tong Vernonica E.
Published: March 2003

Considerable advances have been made, both in the technologies available to study changes in intracellular cytosolic free Ca2+ ([Ca2+]i), and in our understanding of Ca2+ signalling cascades in plant cells, but how specificity can be generated from such a ubiquitous component as Ca2+ is questionable. Recently the concept of ‘Ca2+ signatures’ has been formulated; tight control of the temporal and spatial characteristics of alterations in [Ca2+]i signals is thought to be responsible, at least in part, for the specificity of the response. However, the way in which Ca2+ signatures are decoded, which depends on the nature and location of the targets of the Ca2+ signals, has received little attention. In a few key systems, progress is being made on how diverse Ca2+ signatures might be transduced within cells in response to specific signals. Valuable pieces of the signal‐specificity puzzle are being put together and this is illustrated here using some key examples; these emphasize the global importance of Ca2+‐mediated signal‐transduction cascades in the responses of plants to a wide diversity of extracellular signals. However, the way in which signal specificity is encoded and transduced is still far from clear.

Contents

Summary
7

I.
Introduction: Ca2+ as a signal transducer
8

II.
Alterations in intracellular [Ca2+]
8

1. Measuring alterations in [Ca2+]
8

Imaging [Ca2+]i using Ca2+‐sensitive dyes
8

Measuring [Ca2+]i using aequorin
9

Imaging [Ca2+]i using cameleon
10

2. The concept of the ‘Ca2+ signature
10

3. How might specific Ca2+ signatures be generated?
11

Control of intracellular Ca2+ release
11

Control of influx of extracellular Ca2+
12

4. Examples of Ca2+ signatures and cellular responses to increases in [Ca2+]
13

Ca2+ signatures in stomatal guard cells in response to abscisic acid signals
14

Ca2+ signals in response to abiotic stimuli1
8

Ca2+ signatures involved in plant‐pathogen responses
19

Ca2+signatures in control of plant reproduction
20

Ca2+signatures in root hairs in response to nodulation signals
23

III.
Decoding the [Ca2+]i signatures
24

1. Coupling Ca2+ signals to responses through CaM
26

2. Coupling Ca2+ signals to responses through CDPK
27

3. Novel Ca2+ binding proteins as primary Ca2+ sensors
28

Conclusions and Perspective
28

References
29
Morphological responses of plant roots to heterogeneity of soil resources
Authors: Šmilauerová Marie , Šmilauer Petr
Published: March 2003

• Root morphological response to experimentally induced soil heterogeneity is reported here on three grassland species (Luzula campestris, Poa angustifolia and Plantago lanceolata) under field conditions.

• Nutrient application was combined with suppression of mycorrhizal infection and with substrate structure modification in experimental patches. For each isolated root, we determined five dimensional characteristics and two topological parameters, including a newly introduced topological index (dichotomous branching index).

• Nonmycorrhizal L. campestris responded little to nutrient application, but strongly to benomyl application, in all characteristics measured. Mycorrhizal P. angustifolia produced the longest, most branched roots but exhibited limited sensitivity to nutrients and benomyl application. Strongly mycorrhizal P. lanceolata was the most sensitive to nutrient application, but showed little response to benomyl application. It was the only one among the species studied with root characteristics influenced (negatively) by increased production of total root biomass in the patches. Substrate structure influenced dimensional characteristics of Poa and Luzula roots, but not the topological indices.

• Results indicate different exploitation of soil microsites by L. campestris, P. angustifolia and P. lanceolata. Root topology seems to play a limited role in this process.
Deriving a consistent δ13C signature from tree canopy leaf material for palaeoclimatic reconstruction
Authors: Turney Chris S. M. , Hunt John E. , Burrows Colin
Published: March 2003

Contemporary studies of stable carbon isotope values (δ 13
C) from leaves in the canopies of mature forest indicate that reduced irradiance and respired CO
2
might bias palaeoenvironmental reconstructions developed using the
13 C content of unsorted plant material formed within comparable ancient environments.

Here, we investigated whether any simple morphological and/or chemical characteristics could identify the position of the leaf within a canopy of the evergreen mountain beech ( Nothofagus solandri
var.
cliffortiodes ).

Leaf mass per unit area, carbon content and δ 13 C values of both bulk and lignin components of the leaves increased exponentially from the ground up through the canopy. Nitrogen, remobilized before death, was unsuitable as an indicator of canopy position. Leaf mass per unit area on the forest floor indicated that leaves from the sunlit part comprised approximately 30% of the fallen leaves; leaves originating from the upper canopy made up the remaining litter.

Application of leaf mass per unit area to a 22 000‐yr‐old sequence dominated by mountain beech leaves from Mount George (New Zealand), demonstrated that this signal was preserved in the fossil record. Sunlit leaf material can be successfully differentiated from that originating deeper within the palaeo‐canopy, thereby allowing robust δ 13 C analyses for palaeoenvironmental reconstruction.
An oxidative burst of hydrogen peroxide during rehydration following desiccation in the moss Atrichum androgynum
Authors: Mayaba Nosisa , Minibayeva Farida , Beckett Richard Peter
Published: March 2003

The Afromontane understorey moss Atrichum androgynum
is shown here to display an oxidative burst of hydrogen peroxide (H
2O2) during rehydration following desiccation.

Maximum rates of H 2O2 production, assayed spectrophotometrically using the xylenol orange assay, occurred during the first 15 min of rehydration. Although the production of H2O2 increased with increasing desiccation times, the moss produced significant amounts of H2O2 during rehydration after desiccation for times that did not inhibit photosynthesis or cause potassium (K+) leakage. Atrichum androgynum also produces H2O2 during desiccation; artificially induced desiccation, using polyethylene glycol, strongly stimulates H2O2 production.

Experiments involving inhibitors and exogenously supplied reductants indicated that peroxidases might be responsible for the production of H 2O2. Factors that influence the rate of H2O2 production during rehydration included light and the hormone abscisic acid. Patterns of H2O2 production in A. androgynum are discussed in terms of their possible role in defence against pathogenic fungi and bacteria.
Authentic British food products: a review of consumer perceptions
Authors: Groves Angela M.
Published: March 2003

Historically, soil, land, climatic constraints and individuals’ skills all contributed to the characteristics of regional food. Food, however, is also subject to the influences of colonialism, immigration, cultural exchange, international trade, improved distribution and technology. British food is constantly evolving in order to fulfil the demands of each generation. Thus, the concept of an authentic British food product is becoming increasingly unclear. This paper therefore addresses what today British consumers actually perceive to be authentic British foods. Results of an exploratory qualitative study are reviewed. Five focus groups were conducted with individuals responsible for half or more of their household’s shopping. The groups incorporated consumers with a range of demographic and economic characteristics. The data gathered from the focus groups revealed that British perceptions of authenticity relate to both artisan as well mass‐produced, branded products. In addition, five dimensions affecting consumer perceptions of an authentic British food product were identified, including: uniqueness to Britain, a cultural or traditional association with Britain, characteristics of the production process, the presence of an authority and specific extrinsic characteristics of the product. The findings have implications for product differentiation and communication, for producers and retailers and also for independent trade associations.
Swedish preschool children's experience of food
Authors: Wesslén Annika , Sepp Hanna , Fjellström Christina
Published: March 2003

Focus group interviews were carried out at 12 preschools. The aim was to investigate children's perceptions and experiences of food, and the possibility of using focus group techniques with children aged 3–5 years. A total of 103 children participated. The children associated food and eating with rules and norms. Most children described these rules and norms as well as what they were and were not allowed to do. They knew very well the difference between acceptable and non‐acceptable mealtime behaviour, and were especially aware of what they were not allowed to do. When children were asked to rate foods they ‘disliked’, they spoke instead about their favourite foods. They did not categorize food as good or bad, as adults often do, but as ‘food’ and ‘non‐food’, for example, sweets were not food. The method used in this study, the focus group interview, was judged to be a useful tool for exploring how children think about and jointly reflect upon food.
Milk fats as ingredients
Authors: Burgess Ken J
Published: March 2003

This paper reviews aspects of the use of milk fats as food ingredients from a technico‐marketing perspective. Good marketing involves matching the needs of the market place with the strengths of the supplier relative to those needs. A practical approach to using milk fats as ingredients is therefore based on understanding the background science and technology of milk fats, and on appreciating where the attributes of milk fat in its various forms can deliver real benefits to food manufacturers. These considerations have been addressed in three key areas: what are the characteristics of milk fats; how can the properties of milk fats be modified; and what are the typical milk fat ingredients and their applications.
Increased DNA Oxidation and Decreased Levels of Repair Products in Alzheimer's Disease Ventricular CSF
Authors: Lovell Mark A. , Gabbita S. Prasad , Markesbery William R.
Published: March 2003

Abstract : One of the leading etiologic hypotheses regarding
Alzheimer's disease (AD) is the involvement of free radical‐mediated oxidative
stress in neuronal degeneration. Although several recent studies show an
increase in levels of brain DNA oxidation in both aging and AD, there have
been no studies of levels of markers of DNA oxidation in ventricular CSF. This
is a study of levels of 8‐hydroxy‐2′‐deoxyguanosine (8‐OHdG), the
predominant marker of oxidative DNA damage, in intact DNA and as the
“free” repair product that results from repair mechanisms. Free
8‐OHdG was isolated from CSF from nine AD and five age‐matched control
subjects using solidphase extraction columns and measured using gas
chromatography/mass spectrometry with selective ion monitoring. Intact DNA was
isolated from the same samples and the levels of 8‐OHdG determined in the
intact structures. Quantification of results was carried out using stable
isotope‐labeled 8‐OHdG. By using this sensitive methodology, statistically
significant elevations (p < 0.05) of 8‐OHdG were observed in
intact DNA in AD subjects compared with age‐matched control subjects. In
contrast, levels of free 8‐OHdG, removed via repair mechanisms, were depleted
significantly in AD samples (p < 0.05). Our results demonstrate an increase in unrepaired oxygen radical‐mediated damage in AD DNA as evidenced by the increased presence of 8‐OHdG in intact DNA and decreased concentrations of the free repair product. These data suggest that the brain in AD may be subject to the double insult of increased oxidative stress, as well as deficiencies in repair mechanisms responsible for removal of oxidized bases.