bluuebunny/crossref_metadata_2025_split huggingface dataset:
Patch–background contrast and patch density have limited effects on root proliferation and plant performance in Abutilon theophrasti
Authors: LAMB E. G. , HAAG J. J. , CAHILL J. F. 
Published: December 2004

Summary

We examined biomass and root proliferation responses of Abutilon theophrasti Medic. to the density of high nutrient patches and the patch–background contrast. Contrast in nutrient content between a patch and the background soil, as well as patch density, are important features of heterogeneous soil environments that have received little research attention.
Plants were grown in pots with no, one or two organic nutrient patches, and the equivalent nutrition of no, one or two patches in the background soil in a factorial design. Plant performance (root and shoot biomass) and root proliferation (root length inside and outside high‐nutrient patches) were measured.
Root and shoot biomass increased with increasing nutrient heterogeneity, and root biomass declined with increased background soil nutrient availability. Patch–background contrast did not alter root or shoot biomass, nor allocation to roots. Biomass responses appeared to be driven by heterogeneity, as plants with access to the same total nutrients were larger when nutrients were concentrated in patches. The root proliferation response was not affected by either the density of patches or the degree of contrast.
A conceptual model is presented describing how a plant's overall nutrient status could respond to changes in the patch–background contrast. The model predicts that nutrient‐sufficient plants should not respond to patches, but nutrient‐limited plants should proliferate roots proportionally to the contrast. The proliferation response should saturate when the total nutrients in both patch and background are no longer limiting.
Species richness and susceptibility to heat and drought extremes in synthesized grassland ecosystems: compositionalvsphysiological effects
Authors: VAN PEER L. , NIJS I. , REHEUL D. , DE CAUWER B. 
Published: December 2004

SummaryWe investigated effects of declining plant species richness (S) on resistance to extremes in grassland communities.Synthesized model ecosystems of differentS, grown outdoors in containers, were exposed to a stress peak combining heat and drought. The heat wave was induced experimentally by infrared irradiation in free air conditions.Before the heat wave, the more species‐rich communities produced more biomass as a result of a large and positive complementarity effect that outweighed a small negative selection effect.Water use during the heat wave was likewise enhanced byS, which could not be attributed to dominance of ‘water‐wasting’ species. Instead, water consumption at highSexceeded that expected from changes in community biomass and biomass composition. The observed enhancement of resource (water) acquisition under stress with increasingStherefore probably originated from complementarity.Despite enhanced water use in the more diverse communities, plant survival was significantly less, affecting all species alike. Physiological stress, recorded as photochemical efficiency of photosystem II electron transport, was significantly greater. Before the heat wave, the changes in biomass composition that coincided with increasingSdid not favour species that would later prove intrinsically sensitive or insensitive.Complementarity in resource use for biomass production had a cost in terms of reduced survival under stress, despite the likelihood of complementarity in water acquisition during exposure. The greater loss of individuals from the more diverse grasslands suggests enhanced risk of local extinction.
Increasing accuracy of causal inference in experimental analyses of biodiversity
Authors: BENEDETTI‐CECCHI L. 
Published: December 2004

SummaryManipulative experiments are often used to identify causal linkages between biodiversity and productivity in terrestrial and aquatic habitats.Most studies have identified an effect of biodiversity, but their interpretation has stimulated considerable debate. The main difficulties lie in separating the effect of species richness from those due to changes in identity and relative density of species.Various experimental designs have been adopted to circumvent problems in the analysis of biodiversity. Here I show that these designs may not be able to maintain the probability of type I errors at the nominal level (α = 0·05) under a true null hypothesis of no effect of species richness, in the presence of effects of density and identity of species.Alternative designs have been proposed to discriminate unambiguously the effects of identity and density of species from those due to number of species. Simulations show that the proposed experiments may have increased capacity to control for type I errors when effects of density and identity of species are also present. These designs have enough flexibility to be useful in the experimental analysis of biodiversity in various assemblages and under a wide range of environmental conditions.
Differences between structural and functional environmental heterogeneity caused by seed dispersal
Authors: GÓMEZ J. M. , VALLADARES F. , PUERTA‐PIÑERO C. 
Published: December 2004

Summary

This paper explores the idea that functional heterogeneity (variability of a system property affecting ecological processes) is only a fraction of the available structural heterogeneity (variability of a property measured without reference to ecological effects) caused by non‐random propagule dispersal. We report the effect of acorn dispersal by jays on the light environment experienced by Holm Oaks (Quercus ilex L.) during early recruitment in a Mediterranean montane forest.
Four light variables were estimated by studying hemispherical photographs: direct site factor (DSF); indirect site factor (ISF); and potential direct radiation during April (PDRApril) and August (PDRAugust). Means and variances of these variables were compared before and after the dispersal of acorns by jays.
The landscape occupied by Holm Oaks was very heterogeneous, which translated into differences in the available light among microhabitats of up to one order of magnitude.
Because of the spatial pattern of acorn dispersal, the light environment of the oaks during their establishment was much more homogeneous than that in the whole landscape.
This demonstrates that the heterogeneity relevant for plant recruitment is not necessarily that of the landscape as a whole.
Seasonal variation in the contribution of different behavioural mechanisms to lizard thermoregulation
Authors: DÍAZ J. A. , CABEZAS‐DÍAZ S. 
Published: December 2004

Summary

We studied seasonal changes in the thermoregulatory behaviour of the lacertid lizard Psammodroums algirus in a Mediterranean evergreen forest. Body temperatures (Tb), environmental operative temperatures (Te) and upper and lower limits of the selected thermal range (Tsel) were lower in May than in July.
On average, mean deviations of Tb from Tsel (0·7 °C in both seasons) were much smaller than those of Te (8·3 °C in both seasons). Thus both the accuracy (average difference between Tb and Tsel) and effectiveness (the extent to which Tb are closer than Te to Tsel) of thermoregulation were high, and similar in both seasons.
However the thermoregulatory contribution of two distinct behavioural mechanisms varied markedly between seasons. Daily activity contributed significantly to the regulation of Tb in May (when a population of Te thermometers matching lizard activity patterns would be, on average, 1·0 °C closer to Tsel than were randomly available Te), but not in July (when such a population would be only 0·2 °C closer to Tsel than were randomly available Te). The selection of sun–shade patches, the contribution of which was larger than that of daily activity in both seasons, was more important in July (when it produced a distribution of Te that would be, on average, 3·1 °C closer to Tsel than were randomly distributed Te) than in May (when a population of thermometers matching the lizards’ pattern of exposure to sunlight would be 1·3 °C closer to Tsel than were randomly available Te).
These changes are discussed in the light of seasonal differences in the daily patterns of among‐patch variation in Te. In spring, lizard activity was low in the early morning because even the selection of sunlit patches was of limited utility to attain Tb within Tsel; in summer, lizards could remain active at midday, despite low overall thermal suitability, by selecting shaded patches. Thus the contribution of patch selection to thermoregulation was important in the early basking period of both seasons, and at summer midday hours.
Our data suggest that shuttling between sun and shade, rather than selecting sun or shade, may be an additional mechanism of behavioural thermoregulation, the importance of which would be greatest at times of day when lizards use patches at random (e.g. spring midday hours), and that their mean Tb is closer to the grand mean of full sun and full shade Te than to the mean equilibrium Te within any type of patch.
Morphological acclimation of aquatic Littorella uniflora to sediment CO2 concentration and wave exposure
Authors: BAGGER J. , MADSEN T. V. 
Published: December 2004

Summary

Species of the isoetid life form have many physiological, anatomical and morphological traits that can be seen as adaptations to the environmental characteristics of softwater lakes. Among these, dependence on CO2 from the interstitial water for photosynthesis is one of the more distinctive.
To assess the impact of environmental conditions on morphology and resource allocation of Littorella uniflora (L.) Ascherson, and to test whether CO2 supply from the sediment constrains the maximum attainable leaf length of these plants, a suite of morphological plant traits were measured along a gradient of sediment CO2 availability. The sediment CO2 gradient (0·4–7 mol CO2 m−3 interstitial water) was obtained by collecting specimen from 13 Faroese lakes.
Along the CO2 gradient, the maximum leaf length of the plants more than doubled and was significantly correlated to sediment CO2 concentration. In addition to leaf length, plant size, leaf number and below : above‐ground biomass ratio were also correlated with sediment CO2 concentration, whereas only weak or no correlations between wave exposure and morphological features of the plants were found. Likewise, no correlation between the nutrient status of the plants and morphology was observed.
The results obtained emphasize the importance of sediment CO2 for the performance of L. uniflora and support the suggestion that the maximum attainable leaf length of these plants is set by the CO2 concentration in the interstitial water.
Meta‐analysis: phytotherapy of functional dyspepsia with the herbal drug preparation STW 5 (Iberogast)
Authors: Melzer J. , Rösch W. , Reichling J. , Brignoli R. , Saller R. 
Published: December 2004

SummaryBackground : Despite a long‐standing use of herbal drugs with dyspeptic symptoms, little attention has been paid to their clinical evaluation.Aim : To assess efficacy and safety of the herbal drug preparation STW 5 (containing, e.g. Iberis, peppermint, chamomile) in the treatment of functional dyspepsia.Methods : Research in electronic databases, consultation of experts and of the producer identified STW 5 (Iberogast) as descriptor in six randomized‐controlled trials. The raw data of three placebo‐controlled studies which met the selection criteria, were reanalysed and pooled for meta‐analysis; one reference‐controlled study supported the safety analysis (STW 5: n = 199, control: n = 198).Results : Pooled data showed verum (n = 138) to be more effective than placebo (n = 135) with regard to the severity of the most bothersome gastrointestinal symptom (P‐value: 0.001, odds ratio: 0.22, 95% CI: 0.11–0.47). A fourth randomized‐controlled trial showed no significant difference between STW 5 and cisapride. As to safety, adverse events were similar with verum and placebo; no serious adverse events occurred.Discussions : From the point of view of efficacy and safety, the herbal medicinal product STW 5 appears to be a valid therapeutic option for patients seeking phytotherapy for their symptoms of functional dyspepsia.
Frequency analyses of gastric pH in control and gastro‐oesophageal reflux disease subjects treated with a proton‐pump inhibitor
Authors: Gardner J. D. , Sloan S. , Robinson M. , Miner Jr P. B. 
Published: December 2004

SummaryBackground : We are unaware of any solid theoretical or pathophysiological basis for selecting pH 4 or any other pH value to assess gastric acidity.Aim : To examine the frequency of different gastric pH values in control and GERD subjects.Methods : Gastric pH was measured for 24 h in 26 control subjects, 26 gastro‐oesophageal reflux disease subjects at baseline and the same 26 gastro‐oesophageal reflux disease subjects during treatment with a proton‐pump inhibitor. Histograms were constructed using the 21 600 values generated from each recording and bins of 0.25 pH units.Results : The distribution of gastric pH values in gastro‐oesophageal reflux disease subjects was significantly different from that in controls and in some instances the distributions detected significant differences that were not detected by integrated acidity. Proton‐pump inhibitor treatment significantly altered the distribution of gastric pH values and the nature of this alteration during the postprandial period was different from that during the nocturnal period. Using time pH≤4 can significantly underestimate the magnitude of inhibition of gastric acidity caused by a proton‐pump inhibitor.Conclusions : The distribution of gastric pH values provides a rationale for selecting a particular pH value to assess gastric acidity. In some instances, the distribution of gastric pH values detects significant differences between gastro‐oesophageal reflux disease and normal subjects that are not detected by integrated acidity.
Plant isolation reduces outcross pollen receipt in a partially self‐compatible herb
Authors: DUNCAN DAVID H. , NICOTRA ADRIENNE B. , WOOD JEFF T. , CUNNINGHAM SAUL A. 
Published: December 2004

Summary

Few studies of pollination success in fragmented systems measure stigmatic pollen load, and those that do often find it unrelated to plant or population density, size or isolation. Reduced reproductive output, however, is commonly reported, probably because incompatible pollen is contributing substantially to pollen loads of isolated flowers.
We used manipulated floral arrays of a bee‐pollinated species (Dianella revoluta) to investigate isolation effects on deposition of outcross pollen, while precluding self‐pollen transfer.
Outcross pollen receipt declined significantly over short distances up to approximately 50 m but even the most isolated flowers received some pollen grains. In contrast, heterospecific pollen did not decline, indicating that the outcross‐pollen decline was not due to reduced pollinator visitation. Increased distance of experimental arrays from a nature reserve did not reduce the probability of pollen receipt.
Many flowers were damaged by flower feeding beetles in the genus Arsipoda, which would be likely to substantially reduce the efficiency with which flowers are converted to fruits. The probability of flower damage from these predators was significantly lower in arrays that were more distant from the nature reserve.
This study indicates that reduced plant density and increased isolation from a source of outcrossed pollen can lead to a substantial decline in the probability of outcrossing, even when pollinator visitation is maintained at a high level. Depending on the mating system, this process will lead to reduced seed set or increased inbreeding for plants in fragmented habitats, even when pollinator abundance and behaviour are unaffected.
Ribosomal RNA gene sequence diversity in arbuscular mycorrhizal fungi (Glomeromycota)
Authors: RODRIGUEZ ALIA , CLAPP JUSTIN PETER , DODD JOHN CHARLES 
Published: December 2004

Summary

The existence of multiple rRNA sequences within AMF single spores and the high levels of variability found in these symbionts for highly conserved genes with low copy numbers have provoked intense controversy over the genetic structure of the Glomeromycota. Lately, two hypotheses have been proposed to explain the source of such a variation, mainly either at internuclear (multigenomic) or intranuclear (polyploidy) levels.
Evidence reported by numerous authors suggests that the magnitude of sequence variation, and the presence in single spores of sequences from apparently unrelated taxa within the Glomeromycota, makes the use of one, or very few sequences, from only one or two isolates of AMF insufficient for taxonomic purposes in some species groups.
A large‐scale, collaborative study on genetic variation in AMF across different genes could help to address fundamental questions on the biology and genetic structure of these important symbionts.
Frequency of intravascular catheter colonization by Malassezia spp. in adult patients
Authors: Curvale‐Fauchet Nathalie , Botterel Françoise , Legrand Patrick , Guillot Jacques , Bretagne Stéphane 
Published: December 2004

SummaryColonization of intravascular catheters (IVCs) with lipid‐dependent Malassezia spp. is rarely reported in adult patients probably because of the absence of additional lipids in routine culture media. Therefore, we systematically seeded 983 consecutive IVC onto Dixon medium compatible with the growth of Malassezia spp. Seven (0.7%) IVCs were positive. Six of them were from surgical patients. Four of them also yielded common bacteria. Identification using PCR‐RFLP and restriction enzymes yielded M. furfur and M. sympodialis. Colonization of IVCs with Malassezia spp. does not appear negligible and warrants additional studies to evaluate the clinical relevance of such findings and the role of this yeast in biofilm formation.
Role of
Candida albicans
Transcription Factor Upc2p in Drug Resistance and Sterol Metabolism
Authors: Silver Peter M. , Oliver Brian G. , White Theodore C. 
Published: December 2004

ABSTRACT

In
Candida albicans
, drug resistance to clinically important antifungal drugs may be regulated through the action of transcription factors in a manner that may or may not be similar to regulation in
Saccharomyces cerevisiae
. A search of the
C. albicans
genome identified a single homolog of the
S. cerevisiae
transcription factor genes
UPC2
(
ScUPC2
) and
ECM22
(
ScECM22
) that have been associated with regulation of ergosterol biosynthesis. Sequence analysis of this
C. albicans UPC2
(
CaUPC2
) gene identifies two domains, an anchoring transmembrane domain and a transcription factor region containing multiple nuclear localization signals and a fungal Zn(2)-Cys(6) binuclear cluster domain. Heterozygous deletion, homozygous deletion, and reconstructed strains of
CaUPC2
as well as the parental strain were tested against several antifungal drugs, including ergosterol biosynthesis inhibitors. The
CaUPC2
homozygous deletion strain showed marked hypersusceptibility to most drugs, compared to the parental and reconstructed strains. The deletion strains accumulate significantly less radiolabeled cholesterol, suggesting reduced ergosterol scavenging in those strains. When grown under azole drug pressure, the parental, heterozygous deletion and reconstructed strains of
CaUPC2
upregulate the
ERG2
and
ERG11
ergosterol biosynthesis genes, while the homozygous deletion strain shows no such upregulation. Consistent with these results,
CaUPC2
deletion strains show reduced ergosterol levels, which may explain the increased susceptibilities of the
CaUPC2
deletion strains. Thus, it appears that
CaUPC2
acts as a transcription factor involved in the regulation of ergosterol biosynthetic genes and as a regulator of sterol uptake across the plasma membrane.
FoSTUA, Encoding a Basic Helix-Loop-Helix Protein, Differentially Regulates Development of Three Kinds of Asexual Spores, Macroconidia, Microconidia, and Chlamydospores, in the Fungal Plant PathogenFusarium oxysporum
Authors: Ohara Toshiaki , Tsuge Takashi 
Published: December 2004

ABSTRACTThe soil-borne fungusFusarium oxysporumcauses vascular wilt of a wide variety of plant species.F. oxysporumproduces three kinds of asexual spores, macroconidia, microconidia, and chlamydospores. Falcate macroconidia are formed generally from terminal phialides on conidiophores and rarely from intercalary phialides on hyphae. Ellipsoidal microconidia are formed from intercalary phialides on hyphae. Globose chlamydospores with thick walls are developed by the modification of hyphal and conidial cells. Here we describeFoSTUAofF. oxysporum, which differentially regulates the development of macroconidia, microconidia, and chlamydospores.FoSTUAencodes a basic helix-loop-helix protein with similarity toAspergillus nidulansStuA, which has been identified as a transcriptional regulator controlling conidiation. Nuclear localization of FoStuA was verified by using strains expressing FoStuA-green fluorescent protein fusions. TheFoSTUA-targeted mutants exhibited normal microconidium formation in cultures. However, the mutants lacked conidiophores and produced macroconidia at low frequencies only from intercalary phialides. Thus,FoSTUAappears to be necessary to induce conidiophore differentiation. In contrast, chlamydospore formation was dramatically promoted in the mutants. These data demonstrate that FoStuA is a positive regulator and a negative regulator for the development of macroconidia and chlamydospores, respectively, and is dispensable for microconidium formation in cultures. The disease-causing ability ofF. oxysporumwas not affected by mutations inFoSTUA. However, the mutants produced markedly fewer macroconidia and microconidia in infected plants than the wild type. These results suggest thatFoSTUAalso has an important role for microconidium formation specifically in infected plants.
Deletion of the Three Distal S1 Motifs of
Saccharomyces cerevisiae
Rrp5p Abolishes Pre-rRNA Processing at Site A
2
without Reducing the Production of Functional 40S Subunits
Authors: Vos Harmjan R. , Faber Alex W. , de Gier Maaike D. , Vos Jan C. , Raué Hendrik A. 
Published: December 2004

ABSTRACT

Yeast Rrp5p, one of the few
trans-
acting proteins required for the biogenesis of both ribosomal subunits, has a remarkable two-domain structure. Its C-terminal region consists of seven tetratricopeptide motifs, several of which are crucial for cleavages at sites A
0
to A
2
and thus for the formation of 18S rRNA. The N-terminal region, on the other hand, contains 12 S1 RNA-binding motifs, most of which are required for processing at site A
3
and thus for the production of the short form of 5.8S rRNA. Yeast cells expressing a mutant Rrp5p protein that lacks S1 motifs 10 to 12 (mutant
rrp5Δ6
) have a normal growth rate and wild-type steady-state levels of the mature rRNA species, suggesting that these motifs are irrelevant for ribosome biogenesis. Here we show that, nevertheless, in the
rrp5Δ6
mutant, pre-rRNA processing follows an alternative pathway that does not include the cleavage of 32S pre-rRNA at site A
2
. Instead, the 32S precursor is processed directly at site A
3
, producing exclusively 21S rather than 20S pre-rRNA. This is the first evidence that the 21S precursor, which was observed previously only in cells showing a substantial growth defect or as a minor species in addition to the normal 20S precursor, is an efficient substrate for 18S rRNA synthesis. Maturation of the 21S precursor occurs via the same endonucleolytic cleavage at site D as that used for 20S pre-rRNA maturation. The resulting D
-
A
3
fragment, however, is degraded by both 5′→3′ and 3′→5′ exonuclease digestions, the latter involving the exosome, in contrast to the exclusively 5′→3′ exonucleolytic digestion of the D
-
A
2
fragment. We also show that
rrp5Δ6
cells are hypersensitive to both hygromycin B and cycloheximide, suggesting that, despite their wild-type growth rate, their preribosomes or ribosomes may be structurally abnormal.