bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correlating δ13C and δ18O in cellulose of trees
Authors: SAURER M. , AELLEN K. , SIEGWOLF R. 
Published: November 2003

ABSTRACTWe measured the carbon and oxygen isotopic composition of stem cellulose of Pinus sylvestris, Picea abies, Fagus sylvatica and Fraxinus excelsior. Several sites along a transect of a small valley in Switzerland were selected which differ in soil moisture conditions. At every site, six trees per species were sampled, and a sample representing a mean value for the period from 1940 to 1990 was analysed. For all species, the mean site δ13C and δ18O of stem cellulose are related to the soil moisture availability, whereby higher isotope ratios are found at drier sites. This result is consistent with isotope fractionation models when assuming enhanced stomatal resistance (thus higher δ13C of incorporated carbon) and increased oxygen isotope enrichment in the leaf water (thus higher δ18O) at the dry sites. δ18 O‐δ13C plots reveal a linear relationship between the carbon and oxygen isotopes in cellulose. To interpret this relationship we developed an equation which combines the above‐mentioned fractionation models. An important new parameter is the degree to which the leaf water enrichment is reflected in the stem cellulose. In the combined model the slope of the δ18O‐δ13C plot is related to the sensitivity of the pi/pa of a plant to changing relative humidity.
Temporal and spatial expression of mRNAs encoding pathogenesis‐related proteins during ethylene‐promoted leaflet abscission in Sambucus nigra*
Authors: COUPE S. A. , TAYLOR J‐ E. , ROBERTS J. A. 
Published: November 2003

ABSTRACTDifferential screening of a cDNA library generated from RNA extracted from ethylene‐treated leaflet abscission zones of Sambucus nigra resulted in the isolation of 20 abscission‐related clones. These clones could be grouped into seven families. Sequencing of members of these families revealed that the majority encoded pathogenesis‐related (PR) proteins, and these could be identified by sequence homology as a polyphenol oxidase (PPO), a PR‐1 type protein, a Chial type chitinase, a PR‐4 type protein similar to the potato win peptides, a PR‐6 type proteinase inhibitor, a Chia4 type chitinase and a metallothionein‐like protein (Coupe, Taylor & Roberts 1995, Planta 197, 442–447). Northern analysis revealed that these mRNAs were not expressed in freshly excised material but accumulated primarily in the abscission zone tissue after 18 h of exposure to ethylene at a time when abscission of the leaflet explants had reached 70%. Expression of the PPO and the Chia4‐type chitinase was ethylene‐dependent while that of the PR‐4 type was up‐regulated in the abscission zone tissue in the absence of the gas. The characterization of these mRNAs and their encoded proteins is presented and their possible roles during abscission are discussed.
Relationship between respiratory depletion of sugars and loss of cold hardiness in coniferous seedlings over‐wintering at raised temperatures: indications of different sensitivities of spruce and pine
Authors: ÖGREN E. , NILSSON T. , SUNDBLAD L.‐G. 
Published: November 2003

ABSTRACTLong‐term effects of elevated winter temperatures on cold hardiness were investigated for Norway spruce (Picea abies L. Karst.), lodgepole pine (Pinus contorta Dougl.) and Scots pine (Pinus sylvestris L.). Two‐year‐old seedlings with the same pre‐history of growth and cold hardening in the field were maintained from early December to late March at two field sites in northern Sweden and in a cold room. The temperatures at these locations averaged –13·5, –8·9 and 5·5°C, respectively. Following treatments, carbohydrate contents and cold tolerances were assessed. Needle respiration was also analysed during the 5·5°C treatment. Cold tolerance of lodgepole pine and Scots pine was much reduced following the 5·5°C treatment. Cold tolerance was somewhat reduced in lodgepole pine following the –8·9 °C treatment, but was essentially maintained in spruce throughout all treatments. The cold tolerance of needles was strongly correlated with their soluble sugar contents. Spruce maintained cold hardiness by having larger reserves of sugars and lower rates of respiration which decreased more rapidly as sugars were depleted. Tolerance of lodgepole pine to frost desiccation was also much reduced following the 5·5°C treatment.
Mineral nutrient supply, cell wall adjustment and the control of leaf growth
Authors: SNIR N. , NEUMANN P. M. 
Published: November 2003

ABSTRACTThe possibility that changes in the plasticity of expanding cell walls are involved in regulating early leaf growth responses to nutrient deficiencies in monocot plants was investigated. Intact maize seedlings (Zea mays L.) which were hydroponically grown with their roots in low‐nutrient solution (1 mol m−3 CaCl2) showed early inhibition of first‐leaf growth, as compared with seedlings on complete nutrient solution. This early inhibition of leaf growth was not associated with reduced cell production. However, segmental elongation along the cell expansion zone at the base of the leaf and the lengths of mature epidermal cells were reduced by the low‐nutrient treatment. Solute (osmotic) potentials in the expanding leaf tissues were unchanged. In contrast, low‐nutrient treatments significantly altered leaf plasticity, i.e. the irreversible extension caused by applying a small force in the direction of leaf growth. For example, in vivo plasticity decreased, along with leaf growth, after transfer of seedlings from complete nutrient solution to low‐nutrient solution for 15 h. Conversely, in vivo plasticity increased, along with leaf growth, after transfer of plants previously grown on low‐nutrient solution to complete nutrient solution for 15 h. The nutrient treatments also induced similar changes in the in vitro plasticity of the expanding leaf cell walls. There were no consistent changes in elasticity. Thus, reductions in the plasticity of expanding leaf cell walls appear to be involved in controlling the early inhibition of maize leaf growth by root imposition of nutrient stress.
Effects of low and elevated CO2 partial pressure on growth and reproduction of Arabidopsis thaliana from different elevations
Authors: WARD J. K. , STRAIN B. R. 
Published: November 2003

ABSTRACTAtmospheric CO2 partial pressure may have been as low as 18 Pa during the Pleistocene and is expected to increase from 35 to 70 Pa before the end of the next century. Low CO2 reduces the growth and reproduction of C3 plants, whereas elevated CO2 often increases growth and reproduction. Plants at high elevation are exposed to reduced CO2 partial pressure and may be better adapted to the low CO2 of the Pleistocene. We examined genotypes of Arabidopsis thaliana from different elevations for variation in growth and reproduction at the CO2 levels of the Pleistocene, the present and the future. Genotypes exhibited limited genetic variation in the response of the production of biomass to changes in CO2, but showed significant variation in reproductive characters. We found evidence that plants from high elevations may be better adapted to low CO2 when considering seed number, which is an important component of fitness. Genotypes showed greater variation in the response of seed number between 35 and 20 Pa CO2 compared to 35 and 70 Pa CO2. We conclude that present‐day C3 annuals may have greater potential for evolution in response to the low CO2 of the Pleistocene relative to the elevated CO2 predicted for the future.
Interactions between inorganic phosphate (Pi) assimilation, photosynthesis and respiration in the Pi‐limited green alga Selenastrum minutum*
Authors: GAUTHIER D. A. , TURPIN D. H. 
Published: November 2003

ABSTRACTInorganic phosphate (Pi)‐limited chemostat cultures of the green alga Selenastrum minutum were employed to investigate interactions between Pi assimilation, respiration and photosynthetic processes. Changes in net and gross gas exchange rates indicated that O2 evolution decreases during photosynthetic Pi assimilation. Room temperature and 77K Chi a fluorescence measurements revealed that this photosynthetic suppression is correlated with a transition from state 1 to state 2. Substantial photosynthetic Pi uptake rates occur in the presence of DCMU and KCN. Additionally, the cellular ratio of ATP:NADPH increases following Pi enrichment, suggesting that the ratio of cyclic to linear electron flow is enhanced in response to the high energy requirements of Pi uptake. Net starch degradation was observed during photosynthetic Pi assimilation and the cellular pool size of 3‐phosphoglycerate increased; however, gross gas exchange parameters and cellular metabolite pool sizes indicated that mitochondrial respiration plays a smaller role during Pi assimilation in the light than it does in the dark. These observations were used to formulate a model depicting possible interactions between photosynthetic electron flow, photosynthetic and respiratory carbon metabolism and metabolite exchange between the chloroplast, cytosol and mitochondrion during photosynthetic Pi assimilation.
Dual effect of phytochrome A on hypocotyl growth under continuous red light
Authors: MAZZELLA M. A. , ALCONADA MAGLIANO T. M. , CASAL J. J. 
Published: November 2003

ABSTRACTThe role of phytochrome A in the control of hypocotyl growth under continuous red light (Rc) was investigated using phyA and phyB mutants of Arabidopsis thaliana, which lack phytochrome A (phyA) or phytochrome B (phyB), respectively, and transgenic seedlings of Nicotiana tabacum overexpressing Avena phyA, compared to the corresponding wild type (WT). In WT seedlings of A. thaliana, hypocotyl growth inhibition showed a biphasic response to the fluence rate of Rc, with a brake at 10−2μmol m−2 s−1. At equal total fluence rate, hourly pulses of red light caused slightly more inhibition than Rc. The response to very low fluences of continuous or pulsed red light was absent in the phyA and phyA phyB mutants and present in the phyB mutant. The second part of the response was steeper in the phyA mutant than in the WT but was absent in the phyB mutant. In WT tobacco the response to Rc was biphasic. Overexpression of Avena phyA enhanced the response only at very low fluence rates of Rc (< 10−2μmol m−2 s−1). In both species, the effect of hourly pulses of far‐red light was similar to the maximum inhibition observed in the first phase of the response to Rc. Using reciprocity failure (i.e. higher inhibition under continuous than pulsed light) as the operational criterion, a ‘true’ high‐irradiance reaction occurred under continuous far‐red light but not under Rc or red plus far‐red light mixtures. Native and overexpressed phyA are proposed to mediate very low fluence responses under Rc. In WT A. thaliana, this effect is counteracted by a negative action of phyA on phyB‐mediated low‐fluence responses.
Lognormal distribution of water permeability and organic solute mobility in plant cuticles
Authors: BAUR P. 
Published: November 2003

ABSTRACTIt is shown that water permeabilities and organic solute mobilities in plant cuticles have a lognormal distribution. Seven‐hundred and fifty values for rate constants of desorption (∼mobility) of 2,4‐D from isolated Citrus aurantium L. cuticles from a population of leaves were pooled and analysed. A histogram of the rate constants of individual cuticles showed a skew distribution with a strong tail to higher values. Cuticular membranes with high values did not differ from others in visual appearance and were not leaky. After log‐transformation of original data an almost perfect normal distribution was obtained. Statistical tests showed that a normal distribution of original values is not acceptable. Inspection of older data for water permeability in the same species and experiments using large samples of cuticles from leaves of Pyrus communis L. and Stephanotis floribunda Brongn. and from fruits of Capsicum annuum L. showed a similar distribution, as did inspection of data for experiments with organic solutes. A lognormal distribution was found for cuticles of plants from growth chambers, glasshouses and outdoors as well as for water permeability of intact leaves of Hedera helix L. For small samples the overestimation from using the arithmetic mean of original data can be high, but use of the geometric mean or the median leads to smaller deviations. Removing cuticular waxes from cuticles produced normally distributed samples. A normal distribution was also obtained when organic compounds which increase solute mobility were sorbed into cuticles.
Water potential, turgor and cell wall properties in elongating tissues of the hydrotropically bending roots of pea (Pisum sativum L.)
Authors: HIRASAWA T. , TAKAHASHI H. , SUGE H. , ISHIHARA K. 
Published: November 2003

ABSTRACTThe hydrotropic bending of roots of an ageotropic pea mutant, ageotropum, was studied in humid air in a chamber with a steady humidity gradient. We examined the effects of atmospheric humidity around the root on the water status of root tissues, as well as the wall growth and the hydraulic properties of the elongating tissues. Atmospheric humidity at the surface of the root was clearly lower on the side orientated towards the air with lower humidity than on the side orientated towards the air with higher humidity. However, there were no differences in water potential and osmotic potential between the tissues that faced air with higher and lower humidities in the elongating and mature regions. Plastic extensibility was higher in the tissues that faced the air with lower humidity than in the tissues that faced the air with higher humidity. No differences in turgor pressure and yield threshold were observed between the tissues that faced air with higher and lower humidities. Therefore, the extensibility of the cell wall appeared to be responsible for the different growth rates of tissues in root hydrotropism. A further probable cause of the hydrotropical bending of roots is changes in the hydraulic conductance in the elongating tissues. Since the hydrotropic bending of roots occurred only when a root tip was exposed to a humidity gradient, hydrotropism might occur after perception of a difference in humidity by the root tip, with accompanying changes in cell wall extensibility and hydraulic conductance.
Alterations in light‐induced stomatal opening in a starch‐deficient mutant of Arabidopsis thaliana L. deficient in chloroplast phosphoglucomutase activity
Authors: LASCÈVE G. , LEYMARIE J. , VAVASSEUR A. 
Published: November 2003

ABSTRACTStomatal responses to light of Arabidopsis thaliana wild‐type plants and mutant plants deficient in starch (phosphoglucomutase deficient) were compared in gas exchange experiments. Stomatal density, size and ultrastructure were identical for the two phenotypes, but no starch was observed in guard cells of the mutant plants whatever the time of day. The overall extent of changes in stomatal conductance during 14 h light–10 h dark cycles was similar for the two phenotypes. However, the slow endogenous stomatal opening occurring in darkness in the wild type was not observed in the mutant plants. Stomata in the mutant plants responded much more slowly to blue light (70 μmol m−2 s−1) though the response to red light (250 μmol m−2 s−1) was similar to that of wild‐type plants. In paradermal sections, stomatal responses to red light (300 μmol m−2 s−1) were weak for wild‐type plants as well as for mutant plants. Stomatal opening was greater under low blue light (75 μmol m−2 s−1) than under red light for the two genotypes. However, in mutant plants, a high chloride concentration (50 mol m−3) was necessary to achieve the same stomatal aperture as observed for the wild‐type plants. These results suggest that starch metabolism, via the synthesis of a counter‐ion to potassium (probably malate), is required for full stomatal response to blue light but is not involved in the stomatal response to red light.
Whole‐plant ABA flux and the regulation of water loss in Cedrella odorata
Authors: JARVIS A. J. , DAVIES W. J. 
Published: November 2003

ABSTRACTThree‐month‐old Cedrella odorata seedlings were exposed to a soil‐drying treatment. During this period, xylem sap was periodically collected from the plant by applying pneumatic pressure to the roots. This also allowed whole‐plant water status to be measured by recording the balancing pressure applied. The concentration of ABA in xylem sap (C) was related to the whole‐plant transpiration rate (V) which was measured with a sap flow gauge. The analysis of these paired measurements centred on how the reciprocal of C (R) varied with respect to V. This revealed that (1) the observed increases in C could not be explained by the reductions in V alone, (2) initially, decreases in V were associated with proportional increases in the whole‐plant ABA flux (M), and (3) this relationship broke down at low values of V since zero flow was associated with a finite value for C estimated to be 41 pmol ABA mmol−1 H2O. A simple static model is developed from the observations that is able to explain the data well, and the results are discussed in terms of the effects of ABA on stomatal conductance (gsw).
Acclimation of photosynthesis to irradiance and spectral quality in British plant species: chlorophyll content, photosynthetic capacity and habitat preference
Authors: MURCHIE E. H. , HORTON P. 
Published: November 2003

ABSTRACTTwenty‐two common British angiosperms were examined for their ability to acclimate photosynthetically to sun and shade conditions. Plants were grown under low irradiance, far‐red enriched light (50 μmol m−2 s−1), selected to mimic as closely as possible natural canopy shade, and moderately high light of insufficient irradiance to induce photoinhibitory or photoprotective responses (300 μmol m−2 s−1). Light‐and CO2‐saturated photosynthetic rates of oxygen evolution (Pmax) and chlorophyll content were measured. Large variation was found in both parameters, and two ‘strategies’ for long‐term acclimation were identified: firstly a change in chlorophyll per unit leaf area which was found to correlate positively with photosynthetic capacity, and secondly changes in chlorophyll alb ratio and Pmax, indicative of alterations at the chloroplast level, which were not associated with a change in chlorophyll content per unit leaf area. Combinations of these two strategies may occur, giving rise to the observed diversity in photosynthetic acclimation. The extent and nature of photosynthetic acclimation were compared with an index of shade association, calculated from the association each species has with woodland. It was found that the greatest flexibility for change at the chloroplast level was found in those species possessing an intermediate shade association, whilst acclimation in ‘sun’ species proceeded by a change in chlorophyll content; obligate shade species showed little capacity for acclimation at either the chloroplast or leaf level. A framework for explaining the variation between plant species in leaf‐level photosynthetic capacity, in relation to the natural light environment, is presented. This is the first time the potential for light acclimation of photosynthesis in different plant species has been satisfactorily linked to habitat distribution.
Chromoblastomycosis in India
Authors: Rajendran C. , Ramesh V. , Misra R. S. , Kandhari S. , Upreti H.B. , Datta K. K. 
Published: November 2003

Abstract Background Chromoblastomycosis is reported for the first time from the states of Jammu‐Kashmir and Bihar along with two additional cases from the stales of Assam and Uttar Pradesh. The work carried out on this disease in the Indian subcontinent is reviewed. Methods Relevant mycologic investigations, including direct microscopy, histopathology, and culture, were carried out of study the four cases. Treatment was given to two patients. Results The duration of the lesions varied from 5 to 32 years. In one case the lesion was a large erythematous plaque on the buttocks extending to the backs of the thighs, and in the others they were hypertrophic lesions on the extremities. Histopathologic study of specimens carried out in three patients revealed the causative organisms. On culture, Cladosporium carrionii was isolated in one and Fonsecaea species in the other three. The lesions in one patient were surgically excised and another patient responded well of a combined regimen of amphotericin B and 5‐fluorocytosine. Conclusions Although chromoblastomycosis is widely distributed in India, many patients remain undiagnosed due to a lack of proper facilities. Treatment is difficult and most patients are not able to afford the drugs prescribed for this condition.
Cost‐benefit of oral acyclovir in the treatment of herpes zoster
Authors: Kubeyinje Emmanuel Pandy 
Published: November 2003

Abstract Background Oral acyclovir is a costly antiviral agent shown to be effective in the treatment of herpes zoster. Herpes zoster runs a relatively benign course in young, healthy individuals, as compared with elderly and immunologically compromised patients, in whom complications are common. This study attempts to assess the cost‐benefit of treatment with oral acyclovir in young healthy adults with herpes zoster. Patients and methods The records of 42 healthy young adults suffering from herpes zoster and treated with oral acyclovir (800 mg five times daily for 7 days) were compared with those of 40 healthy young adults with herpes zoster seen during the same period but treated without oral acyclovir. The duration of zoster‐associated pain and the presence of complications were noted. Results There was no statistically significant difference in the duration of zoster‐associated pain between the two groups of patients (P= 0.11). Other complications of herpes zoster were few and similar in the two groups. Conclusions At a cost of $250 to $300 for a 7–day course of oral acyclovir, the use of this antiviral agent in healthy young individuals with herpes zoster is not justified, especially in developing countries with limited resources.
Angiocentric T‐cell lymphoma presenting as lethal midline granuloma
Authors: Lee Peter Y. , Freeman Nancy J. , Khorsand Jila , Weinstock Martin A. 
Published: November 2003

Abstract Background Lethal midline granuloma (LMG) is a rare condition characterized by rapidly progressive midfacial destruction. Most LMG cases are angiocentric T‐cell lymphomas and an association with Epstein‐Barr virus (EBV) has been reported. Cutaneous involvement is poorly described and the prognosis not well documented. Methods We report a case of angiocentric T‐cell lymphoma of the palate that presented as LMG with concurrent discrete skin lesions composed of two distinct morphologic appearances: indurated nodules and annular plaques. The English language literature for LMG‐type angiocentric T‐cell lymphoma is reviewed and a survival analysis of 58 cases with follow‐up data (including our own case) is performed. Results The 1‐ and 5‐year survival rates were 45%± 7% and 22%± 9%, respectively. Poor survival was associated with advanced age and stage. EBV DNA was detected in 16 out of 21 reported cases in which it was sought (including our case). Conclusions We present photographic documentation of a broader spectrum of cutaneous lesions in the LMG‐type angiocentric T‐cell lymphoma than has previously been described, and have confirmed the association with EBV. The prognosis is poor. Aggressive therapy such as bone marrow transplantation should be considered early in the course.