bluuebunny/crossref_metadata_2025_split huggingface dataset:
The selective advantage of buoyancy provided by gas vesicles for planktonic cyanobacteria in the Baltic Sea
Authors: WALSBY ANTHONY E. , HAYES PAUL K. , BOJE ROLF , STAL LUCAS J. 
Published: March 2003

summaryObservations were made on the vertical distribution of colonies of Aphanizomenon flos‐aquae for 9 d at a drift‐station east of Bornholm Island in the Baltic Sea. The buoyant colonies were dispersed in the upper layers of the water column during periods of wind‐induced mixing but floated up during calm periods. From measurements of the vertical light extinction, surface irradiance and the photosynthesis versus irradiance curve, calculations were made of the changes in the daily integral of photosynthesis with respect to time and depth throughout the water column. From these calculations it is demonstrated that net photosynthesis by the population of Aphanizomenon flos‐aquae increased nearly threefold by floating up after a deep mixing event. It is estimated that, averaged over alternating periods of calm and mixing, the buoyancy provided by gas vesicles in this organism will result in a nearly twofold increase in photosynthesis. A quantitative analysis has been made of the relationship of the daily integral of photosynthesis by the Aphanizomenon population with the mean depth of the population in the water column and the daily insolation. The analysis shows that the integral decreases linearly with respect to mean depth.
Physiological changes on agricultural crops induced by different ambient ozone exposure regimes
Authors: MEYER U. , KÖLLNER B. , WILLENBRINK J. , KRAUSE G. H. M. 
Published: March 2003

SUMMARYSpring wheat (Triticum aeslivum cv. Nandu) cultivated under glasshouse conditions was exposed to ozone in large fumigation chambers for 2 wk. Different exposure regimes were applied as constant concentrations as well as with ozone peaks, partly under equal dose‐conditions, in times of high solar radiation during different stages of development (seedling, late tillering, anthesis). Chlorophyll fluorescence was monitored and amounts of carbohydrates (hexoses, sucrose, starch) and chlorophyll were measured in young leaves (seedling) and flag leaves (late tillering, anthesis) during and after ozone exposure. Although seedlings showed no significant response in photosynthesis, strong effects on photosynthesis and carbohydrate accumulation were measured when plants were fumigated during anthesis, especially after a heat stress period preceding ozone treatments. Under equal dose conditions chlorophyll fluorescence parameters (Fv:Fm) and electron transport rate decreased and sucrose content of flag leaves increased significantly if ozone at a concentration of 220 μg m−3 was supplied for 4 h, indicating that peak concentrations show stronger effects than constant concentrations. The reaction of wheat plants is dependent on environmental conditions such as preceding heat stress and on the developmental stage during exposure. The results favour the hypothesis that photoinhibition and disturbance of photosynthesis are only secondary effects as a consequence of retarded sucrose export from the leaf, because of damage at the plasma membrane.
Quantitative trait loci associated with stomatal conductance, leaf rolling and heading date mapped in upland rice (Oryza sativa)
Authors: PRICE A. H. , YOUNG E. M. , TOMOS A. D. 
Published: March 2003

summaryImproving the drought resistance of high yielding rice (Oryza sativa L.) varieties for upland areas is a goal of rice breeders since upland rice relies exclusively on rainfall for water and is generally low yielding. Identifying quantitative trait loci (QTLs) which confer drought resistance promises to speed this goal. We have previously described the use of 82 restriction fragment length polymorphism (RFLP) markers in the genetic mapping of root growth characteristics that are potentially involved in drought resistance in a population of 178 F2 plants derived from a cross of two drought resistant upland varieties, Azucena and Bala. Here we report the characterization and QTL mapping of three other mechanisms of drought resistance, leaf rolling, stomatal behaviour and early flowering, in this population. When the youngest fully expanded leaf was excised from 12 rice varieties,‘IR20’and‘Bala’ were identified as slow at rolling. Although ‘Azucena’ rolled its leaves much faster than ‘Bala’ upon excision, stomatal resistance rose more rapidly in‘Bala’, resulting in a lower rate of water loss. By assessing leaf rolling and stomatal resistance in the F2 population, it was possible to identify QTLs for these traits. A QTL for slow leaf rolling from ‘Bala’ was found on chromosome 1. Two QTLs associated with resting stomatal conductance were found on chromosomes 3 and 12. QTLs for the rate of stomatal closure were found on chromosomes 3 and 7. In addition, it was possible to map QTLs associated with the days to heading which were found on chromosomes 3, 8 and 10. These results identify markers of potential value to breeders and are discussed in the context of previously reported data for heading date QTLs in rice and for stomatal conductance QTLs in maize.
Toxic interactions of metal ions (Cd2+, Pb2+, Zn2+ and Sb3−) on in vitro biomass production of ectomycorrhizal fungi
Authors: HARTLEY JEANETTE , CAIRNEY JOHN W. G. , SANDERS FRANCIS E. , MEHARG ANDREW A. 
Published: March 2003

summaryA number of ectomycorrhizal (ECM) fungi, from sites uncontaminated by toxic metals, were investigated to determine their sensitivity to Cd2+, Pb+2, Zn2+ and Sb3−, measured as an inhibition of fungal biomass production, Isolates were grown in liquid media amended with the metals, Individually (over a range of concentrations) and in combination (at single concentrations) to determine any significant interactions between the metals. Significant interspecific variation in sensitivity to Cd2+ and Zn2+ was recorded, while Pb2+ and Sb3− individually had little effect. The presence of Pb2+ and Sb3− in the media did however, amcliorate Cd2+ and Zn2+ toxicity in some circumstances. Interactions between Cd+2 and Zn+2 were investigated further over a range of concentrations. Zn2+ was found to significantly ameliorate the toxicity of Cd2+ to three of the four isolates tested. The influence of Zn2+varied between ECM species and with the concentrations of metals tested.
Initial stages of lichen hydration observed by proton magnetic relaxation
Authors: HARAŃCZYK H. , GAŹDZIŃSKI S. , OLECH M. 
Published: March 2003

The hydration of selected lichens (Cladonia mitis, Cladonia bellidiflora, Cetraria islandica, Parmelia saxatilis, and Xanthoria parietina) was investigated using gravimetry and proton magnetic free induction decays (FIDs).The hydration from gaseous phase and dehydration to gaseous phase showed first‐order kinetics. The amount of water which was non‐removable in the air‐dry state (relative humidity p/p0=9%) did not depend significantly on the lichen species and was found to be 5·6±1·0% of the d. wt.The proton FID Gaussian component from the solid matrix of thallus structure, and two (or, depending on lichen species, one averaged) liquid signals coming from water tightly bound on the surface of thallus solid matrix and from loosely bound or free water, were recorded. The bound‐water component was distinguished by its motional properties and by its proximity to endogenous paramagnetic centres present in solid matrix (presumably PS II reaction centres of the photobiont). Mild dehydration (from gaseous phase) could completely remove the loosely bound water fraction, leaving the system below the water percolation threshold and below the water clustering point, emphasizing the passivity of lichen response to desiccation shock. In the species in which the one average liquid component was recorded, bound water behaved similarly.The hydration at which free water pool vanishes (ΔM/m0) and the relative (scaled to water) proton densities of solid matrix of lichen (β) were evaluated for all lichens investigated.
Impacts of ozone on forests: a European perspective
Authors: SKÄRBY LENA , RO‐POULSEN HELGE , WELLBURN FLORENCE A. M. , SHEPPARD LUCY J. 
Published: March 2003

In comparison with the effects of extended drought periods or severe nutrient stress, those of ozone are generally much milder, at least with respect to growth. However, there is substantial evidence from experiments, in the main using young saplings, that O3 does impose a stress on forest trees under European conditions. Decreased chlorophyll contents and photosynthetic rates, changes in carbon allocation, increased antioxidant activity, and reductions in biomass due to O3 have often been recorded, particularly in fast‐growing species. Furthermore, 3 appears to weaken the trees' resilience to a range of biotic and abiotic stresses. Interactions between O3 and climatic stress, in particular drought and frost hardiness, are likely to result in potentially detrimental effects.A link between the occurrence of O3 and forest damage is not unequivocally established in Europe, and the problem remains of extrapolating and/or scaling up from studies on seedlings to predict responses to O3 of mature trees and forest stands, because we know so little about acclimation to O3. An accurate assessment is also lacking of the magnitude of the O3 effect on European trees both in terms of the forest areas affected and its extent. In this review we suggest that C allocation is the key factor underlying the responses of trees to O3. Stomata also play a key role, since the acquisition of C must be achieved while an effective control over water consumption is retained.
In situ studies of water relations and CO2 exchange of the tropical macrolichen, Sticta tomentosa
Authors: ZOTZ G. , BÜDEL B. , MEYER A. , ZELLNER H. , LANGE O. L. 
Published: March 2003

Diel (24‐h) time courses of CO2 exchange, water relations, and microclimate of the foliose lichen, Sticta tomentosa (Swartz) Ach., and responses to experimentally manipulated conditions were measured at a forest edge in a lower montane rainforest in Panama.Similar to earlier observations on two other rain forest lichens, daily desiccation suppressed net photosynthesis (NP) during the period when irradiation was highest. Not surprisingly, the light response curves of NP showed saturation at rather low light levels. Rehydration was associated with an initial resaturation burst of short duration, which could be demonstrated both under natural conditions and experimentally. This additional loss of CO2 seems too low to be ecologically relevant. Moreover, high thallus hydration was also detrimental to NP: at maximum water content net CO2 uptake was depressed by >50%. Although NP was well adapted to the prevailing high temperatures, the latter also stimulated dark respiration. On average, almost 60% of the diurnal carbon gain was lost during the night.In spite of these limitations, the integrated 24‐h C gain was quite high, on average 0·5% of the thallus C content. Whilst these figures were determined for horizontally exposed samples, we also assessed the role of different exposures on photosynthetic performance. Diel C gain was highest under conditions of semi‐shade (westerly exposure), which allowed long periods of activity, whilst much higher irradiance at other exposures could not be utilized for photosynthetic production: easterly exposed thalli dried out even faster than horizontally exposed samples.
Physiological evidence for a high‐affinity cadmium transporter highly expressed in a Thlaspi caerulescens ecotype
Authors: Lombi E. , Zhao F. J. , McGrath S. P. , Young S. D. , Sacchi G. A. 
Published: March 2003

Abstract• Uptake kinetics and translocation characteristics of cadmium and zinc are presented for two contrasting ecotypes of the Cd/Zn hyperaccumulator Thlaspi caerulescens, Ganges (southern France) and Prayon (Belgium).• Experiments using radioactive isotopes were designed to investigate the physiology of Cd and Zn uptake, and a pressure‐chamber system was employed to collect xylem sap.• In contrast to similar Zn uptake and translocation, measurements of concentration‐dependent influx of Cd revealed marked differences between ecotypes. Ganges alone showed a clear saturable component in the low Cd concentration range; maximum influx Vmax for Cd was fivefold higher in Ganges; and there was a fivefold difference in the Cd concentration in xylem sap. Addition of Zn to the uptake solution at equimolar concentration to Cd did not decrease Cd uptake by Ganges, but caused a 35% decrease in Prayon.• There is strong physiological evidence for a high‐affinity, highly expressed Cd transporter in the root cell plasma membranes of the Ganges ecotype of T. caerulescens. This raises evolutionary questions about specific transporters for non‐essential metals. The results also show the considerable scope for selecting hyperaccumulator ecotypes to achieve higher phytoextraction efficiencies.
Ancestry of KNOX genes revealed by bryophyte (Physcomitrella patens) homologs
Authors: Champagne Connie E. M. , Ashton Neil W. 
Published: March 2003

Summary

Structural and phylogenetic studies of KNOX
genes identified in the bryophyte
Physcomitrella patens
are reported here, to provide insights into the evolution of class 1 and class 2
KNOX genes.
Three KNOTTED1
‐like homeobox (
KNOX
) genomic clones were isolated and sequenced from
P. patens . Corresponding cDNAs from a library, prepared from mRNA transcripts isolated from gametophytic tissues, were also sequenced.
Conceptual translation and analysis of the bryophyte coding sequences revealed a domain pattern and secondary structures typical of higher plant KNOX proteins. Intron number and positions within the genes were also highly conserved between moss and angiosperm loci, providing further support for their homology. Structural and phylogenetic analyses indicated that moss clones ( MKN2
and
MKN4
) represent class 1
KNOX
genes and the remaining clone (
MKN1–3
) is a class 2
KNOX gene.
We conclude that the observed protein domain pattern is encoded by homeobox genes that evolved after separation of the plant lineage from that of fungi and animals, and must have been present in the common ancestor to mosses and seed plants. It is proposed that gene duplication and diversification, which created class 1 and 2 KNOX
gene subfamilies, occurred after separation of this common ancestor from its algal progenitor (since a characterized algal
KNOX gene cannot be assigned to class 1 or 2), but before the moss and higher plant lineages diverged.
Phosphorus uptake by arbuscular mycorrhizal hyphae does not increase when the host plant grows under atmospheric CO2 enrichment
Authors: Gavito Mayra E. , Bruhn Dan , Jakobsen Iver 
Published: March 2003

Summary• We conducted an experiment to test whether phosphorus (P) uptake by mycorrhizal hyphae could be enhanced by growing the host plant under [CO2] enrichment and whether any response to [CO2] was dependent on C source‐sink relationships.• Plant C assimilation, mass allocation, growth and P uptake were measured in pea (Pisum sativum) plants inoculated with 0, 1 or 5% of a mixture of three Glomus spp. Intra‐ and extra‐radical mycorrhizal development was followed and hyphal 33P uptake from a root‐exclusion compartment was measured.• Total P and 33P content measurements indicated that root, not hyphal, P uptake was increased by elevated [CO2] in the mycorrhizal treatments and that hyphal P uptake was actually reduced by elevated [CO2] after 57 d. Neither intra‐ nor extraradical mycorrhizal development was related to this response.• Plant and fungal measurements suggested positive interactions in plant growth and P uptake only when C source‐sink relationships were balanced; high C source (enhanced assimilation at elevated [CO2]) and high C sink (increasing mycorrhizal development). The results also indicated that enhanced plant C supply does not alter growth or function of arbuscular mycorrhizal fungi.
Insect‐mediated reproduction of systemic infections by Puccinia arrhenatheri on Berberis vulgaris
Authors: Naef Andreas , Roy Bitty A. , Kaiser Roman , Honegger Rosmarie 
Published: March 2003

Summary• Witches’ brooms on Berberis vulgaris are induced by a systemically infecting rust fungus, Puccinia arrhenatheri. These witches’ brooms bear yellow discolored leaves on which the fungus exposes its gametes in a sugary nectar. During the spermatial stage of the fungus the infected leaves emit a strong, flowery scent.• An exclusion‐experiment was used to evaluate whether fungal reproductive success, defined by the ability of the fungus to produce aeciospores, depended on gamete transfer by insects. To determine whether insects were attracted to the infected leaves, and if so, why, visitation to infected and uninfected leaves was quantified and volatiles produced by leaves, infected leaves and flowers were analyzed.• The production of aeciospores was significantly higher on witches’ brooms with insect visitation. Visitation rates were higher and visits were longer on witches’ brooms than on uninfected branches. A wide diversity of visitors, mainly Diptera and Hymenoptera, was observed. The volatiles emitted by infected leaves were composed of sweet floral fragrances and insect pheromones.• Our results suggest that sexual reproduction of the pathogen requires out‐crossing by insects and that infected leaves attract insects by floral mimicry (bright yellow color and the production of sugary nectar and volatiles).
The cell biology of phytochrome signalling
Authors: Møller Simon G. , Ingles Patricia J. , Whitelam Garry C. 
Published: March 2003

SummaryPhytochrome signal transduction has in the past often been viewed as being a nonspatially separated linear chain of events. However, through a combination of molecular, genetic and cell biological approaches, it is becoming increasingly evident that phytochrome signalling constitutes a highly ordered multidimensional network of events. The discovery that some phytochromes and signalling intermediates show light‐dependent nucleo‐cytoplasmic partitioning has not only led to the suggestion that early signalling events take place in the nucleus, but also that subcellular localization patterns most probably represent an important signalling control point. Moreover, detailed characterization of signalling intermediates has demonstrated that various branches of the signalling network are spatially separated and take place in different cellular compartments including the nucleus, cytosol, and chloroplasts. In addition, proteasome‐mediated degradation of signalling intermediates most probably act in concert with subcellular partitioning events as an integrated checkpoint. An emerging view from this is that phytochrome signalling is separated into several subcellular organelles and that these are interconnected in order to execute accurate responses to changes in the light environment. By integrating the available data, both at the cellular and subcellular level, we should be able to construct a solid foundation for further dissection of phytochrome signal transduction in plants.

Contents

Summary
553

I.
Introduction
554

II.
Nucleus vs cytoplasm
556

III.
The nucleus
562

IV.
The cytoplasm
571

V.
Interactions with other signalling pathways
577

VI.
Conclusions and the future
582

Acknowledgements
583

References
583
Implications of leaf nitrogen recycling on the nitrogen isotope composition of deciduous plant tissues
Authors: Kolb K. J. , Evans R. D. 
Published: March 2003

SummaryThe effect of nitrogen (N) recycling on tissue δ15N was studied using drought‐deciduous shrubs (Encelia farinosaandE. frutescens) and deciduous trees (Quercus rubraandQ. alba) to determine if isotope discrimination occurs with N reabsorption or reallocation.There was substantial reabsorption of leaf nitrogen before abscission in all species, yet there was no difference in the δ15N of living vs abscised leaves, suggesting no isotope discrimination with reabsorption. However, the contribution of stored N for leaf production resulted in a difference in foliar and absorbed nitrogen δ15N, suggesting that isotope discrimination occurs with reallocation.The contribution of stored nitrogen to leaf production varied with timing of leaf development: leaves produced first had a δ15N that reflected utilization of both absorbed and stored N, yet the contribution of stored N decreased over time.The results from this study as well as previous research on intraplant variation in isotopic composition suggest that caution needs to be exercised when interpreting foliar δ15N because it is not always a reliable indicator of whole‐plant δ15N.
An approach to the detection of synthetic milk in dairy milk: 3. Detection of vegetable oil and sodium bicarbonate
Authors: Paradkar Manish M , Singhal Rekha S , Kulkarni Pushpa R 
Published: March 2003

A high‐performance thin layer chromatography (HPTLC) method for the detection of groundnut oil and palm oil, the main constituents of synthetic milk, was developed. The minimum detectable level of the oils was 80 mg/100 ml. The rosolic acid qualitative test was found to be sensitive enough to detect levels as low as 20 mg/100 ml sodium bicarbonate in milk.
Changes in the microbiological and chemical characteristics of an artisanal, low‐fat cheese made from raw ovine milk during ripening
Authors: Nikolaou E , Tzanetakis N , Litopoulou‐Tzanetaki E , Robinson R K 
Published: March 2003

Changes in the microbial flora of batzos cheese made from raw ovine milk were studied during ripening. Lactic acid bacteria and Enterobacteriaceae were the predominant groups of micro‐organisms. Cheeses manufactured in summer had higher microbial counts than those made in spring, with the exception of staphylococci. Nevertheless, Enterobacteriaceae and coliforms decreased more rapidly in cheese made in summer and counts at the end of storage were lower than those in spring cheese.Enterococci predominated in the ripened curd of cheese made in spring, whereas lactobacilli were the most abundant lactic acid bacteria in cheese made in summer. Enterococcus faecium was the predominant species in spring, and Lactobacillus paracasei ssp. paracasei predominated in cheese made in summer. The pH of the cheeses was > 5.0 throughout ripening, and NaCl‐in‐moisture content (> 8.0%) permitted the growth and survival of salt‐tolerant micro‐organisms. αs1‐Casein degraded at a faster rate than β‐casein; both caseins were hydrolysed more rapidly in spring than in summer. The free amino acid content became higher in summer cheese (566.24–3460.25 µg/g of glycine equivalent) than in spring cheese because of the progress of ripening. Moreover, the milk fat of the cheese was degraded more in the summer than in the spring. The results suggest that there could be advantages to using starter cultures and improving the level of hygiene during milk and cheese production in order to eliminate undesirable micro‐organisms and standardize cheese quality.