bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermographic visualization of cell death in tobacco and Arabidopsis
Authors: Chaerle L. , De Boever F. , Montagu M. Van , Straeten D. Van Der 
Published: March 2003

ABSTRACTPending cell death was visualized by thermographic imaging in bacterio‐opsin transgenic tobacco plants. Cell death in these plants was characterized by a complex lesion phenotype. Isolated cell death lesions were preceded by a colocalized thermal effect, as previously observed at sites infected by tobacco mosaic virus (TMV) (Chaerle et al. 1999Nature Biotechnology 17, 813–816). However, in most cases, a coherent front of higher temperature, trailed by cell death, initiated at the leaf base and expanded over the leaf lamina. In contrast to the homogenous thermal front, cell death was first visible close to the veins, and subsequently appeared as discrete spots on the interveinal tissue, as cell death spread along the veins. Regions with visible cell death had a lower temperature because of water evaporation from damaged cells. In analogy with previous observations on the localized tobacco–TMV interaction (Chaerle et al. 1999), the kinetics of thermographic and continuous gas exchange measurements indicated that stomatal closure preceded tissue collapse. Localized spontaneous cell death could also be presymptomatically visualized in the Arabidopsis lsd2 mutant.
The guard‐cell apoplast as a site of abscisic acid accumulation in Vicia faba L.
Authors: Zhang S. Q. , Outlaw W. H. 
Published: March 2003

ABSTRACTAbscisic acid (ABA) integrates the water status of a plant and causes stomatal closure. Physiological mechanisms remain poorly understood, however, because guard cells flanking stomata are small and contain only attomol quantities of ABA. Here, pooled extracts of dissected guard cells of Vicia faba L. were immunoassayed for ABA at sub‐fmol sensitivity. A pulse of water stress was imposed by submerging the roots in a solution of PEG. The water potentials of root and leaf declined during 20 min of water stress but recovered after stress relief. During stress, the ABA concentration in the root apoplast increased, but that in the leaf apoplast remained low. The ABA concentration in the guard‐cell apoplast increased during stress, providing evidence for intra‐leaf ABA redistribution and leaf apoplastic heterogeneity. Subsequently, the ABA concentration of the leaf apoplast increased, consistent with ABA import via the xylem. Throughout, the ABA contents of the guard‐cell apoplast, but not the guard‐cell symplast, were convincingly correlated with stomatal aperture size, identifying an external locus for ABA perception under these conditions. Apparently, ABA accumulates in the guard‐cell apoplast by evaporation from the guard‐cell wall, so the ABA signal in the xylem is amplified maximally at high transpiration rates. Thus, stomata will display apparently higher sensitivity to leaf apoplastic ABA if stomata are widely open in a relatively dry atmosphere.
Computer‐based analysis of steady‐state and transient heat transfer of small‐sized leaves by free and mixed convection
Authors: Roth‐Nebelsick A. 
Published: March 2003

AbstractIn order to study convective heat transfer of small leaves, the steady‐state and transient heat flux of small leaf‐shaped model structures (area of one side = 1730 mm2) were studied under zero and low (= 100 mm s−1) wind velocities by using a computer simulation method. The results show that: (1) distinct temperature gradients of several degrees develop over the surface of the model objects during free and mixed convection; and (2) the shape of the objects and onset of low wind velocities has a considerable effect on the resulting temperature pattern and on the time constant τ. Small leaves can thus show a temperature distribution which is far from uniform under zero and low wind conditions. The approach leads, however, to higher leaf temperatures than would be attained by ‘real’ leaves under identical conditions, because heat transfer by transpiration is neglected. The results demonstrate the fundamental importance of a completely controlled environment when measuring heat dissipation by free convection. As slight air breezes alter the temperature of leaves significantly, the existence of purely free convection appears to be questionable in the case of outdoor conditions. Contrary to the prognoses yielded by standard approximations, no quantitative effect of buoyancy on heat transfer under the considered conditions could be detected for small‐sized leaf shapes.
Rate of acclimation of the capacity for isoprene emission in response to light and temperature
Authors: Hanson D. T. , Sharkey T. D. 
Published: March 2003

AbstractIsoprene emission from plants accounts for nearly half of all non‐methane hydrocarbons entering the atmosphere. Light and temperature regulate the instantaneous rate of isoprene emission but there is increasing evidence that they also affect the capacity for isoprene emission (i.e. the rate measured under standard conditions). We tested the rate of acclimation of the capacity for isoprene emission following step changes in growth conditions. Acclimation to new growth temperatures was very rapid, with most of the change occurring within a few hours and complete adjustment occurring within a day. Acclimation to new light levels was more complicated. Following a switch from low‐light growth conditions to standard assay conditions (30 °C and 1000 µmol photons m−2 s−1), there was a rapid (5–10 min) and a slightly slower (10–50 min) acclimation of the capacity for isoprene emission. After accounting for these short‐term changes, there was also a small, long‐term (4–6 d) acclimation of the isoprene emission capacity to the light level of growth conditions. We found no effect of growth conditions on the coefficients used to describe the instantaneous light and temperature response of isoprene emission. Therefore, current models of isoprene emission will only need to be altered to account for changes in the capacity for isoprene emission.
Fluorescence and photochemical properties of phytochromes in wild‐type wheat and a transgenic line overexpressing an oat phytochrome A (PHYA) gene: functional implications
Authors: Sineshchekov V. , Koppel L. , Shlumukov L. , Barro F. , Barcelo P. , Lazzeri P. , Smith H. 
Published: March 2003

AbstractEtiolated seedlings of wild‐type wheat and a transgenic line overexpressing an oat PHYA gene were investigated by the use of in situ low‐temperature fluorescence spectroscopy. The red‐absorbing phytochrome form, Pr, was characterized by (1) fluorescence emission spectrum; (2) total phytochrome content, and (3) by the extent of the Pr → lumi‐R photoconversion at low temperature (γ1), and of the Pr → Pfr photoconversion at ambient temperature (γ2) as derived from emission data. All the characteristics were shown to be variable and to depend on (1) organ and tissue used; (2) seedling age; (3) transgenic wheat modification, and (4) continuous far‐red irradiation of seedlings during their growth. These variations were interpreted in terms of the existence in wheat seedlings of the two phenomenological Pr types: (a), Pr′– major longer wavelength (687/673 nm, emission/absorption maxima) variable and light‐labile with γ1 ≈ 0·5; and (b), Pr′′– minor, shorter wavelength (682/668 nm), relatively constant with its concentration not changing significantly with the increase of total phytochrome content in tissues and light‐stable with γ1 ≤ 0·05–0·1. Overexpression of oat phyA increases primarily the content of Pr′ suggesting that it is comprised of phyA (phyA′) whereas Pr′′ is believed to consist of the minor phyA fraction (phyA′′) and phyB. The transgenic wheat line has been demonstrated to have a modified phenotype – the appearance of the far‐red high irradiance reaction (FR‐HIR) (Shlumukov et al. Plant, Cell and Environment 24, 703–712). The increased content of phyA′ in the transgenic line, whereas the total [phyA′′ + phyB] remains the same as in the wild type, indicates that the phyA′ pool is primarily responsible for the observed modification of the phenotype and suggests that even in wild‐type plants the phyA′ component of the phyA pool may mediate the FR‐HIR.
The effect of three rootstocks on water use, canopy conductance and hydraulic parameters of apple trees and predicting canopy from hydraulic conductance
Authors: Cohen S. , Naor A. 
Published: March 2003

AbstractThis study investigated the effect of the dwarfing M9, semi‐dwarfing MM106 and local Hashabi rootstocks on the water use, canopy conductance (Gc) and hydraulic conductance (k) of apple orchards with the same scion, Golden Delicious. The average summer leaf area index (LAI) was 2·4, 2·7 and 1·7 for M9, MM106 and Hashabi, respectively. Irrigation in 1997 was less than water use until June, and excessive afterwards. In 1998, irrigation was doubled, and was excessive throughout the season. Sap flow (J) in June–August 1998 totalled 476, 682 and 606 mm (or 0·60, 0·86 and 0·76 of class A pan evaporation) for M9, MM106 and Hashabi, respectively. Maximum sap velocity in the three rootstocks (approximately 70 cm h−1) occurred in the outer 30–60% of the stem, and its decrease with depth was greater in M9 than in the other rootstocks. Midday Gc during both summers was least for M9, intermediate for Hashabi and greatest for MM106. The k value of M9 and MM106 for the soil to stem, stem to leaves and soil to leaves pathways were determined from daily courses of water potential of leaves, Ψl, stem, Ψstem and J. Specific k (ks, i.e. relative to stem sapwood area) did not significantly differ between the two rootstocks for soil to stem and soil to leaf pathways, but leaf specific k (kl) was greater for MM106 soil to stem (71% greater) and soil to leaf (63%) pathways, respectively. The inverse slopes of the relationships between midday canopy resistance (Rc) and vapour pressure deficit (D) for MM106 was 1·75 of that for M9, and the ratio of their Huber values, i.e. the ratio of sapwood to leaf area, was 1·6. These findings indicate that differences in water use are attributable to differences in kl, and not to differences in wood properties (ks). Application of a model relating Rc to orchard area specific k (kg) showed that the slope of the relationships between midday Rc and D for the 1998 data could be predicted using common values of ks (0·134 kg m−2 s−1 MPa−1) and midday Ψl (−1·34 MPa) for the three rootstocks. The implications of these findings, and the similarities in the differences between rootstocks of Gc, kl, kg and Huber values, are discussed with respect to rootstock water use and irrigation.
Scaling relationships for woody tissue respiration in two tropical rain forests
Authors: Meir P. , Grace J. 
Published: March 2003

AbstractThe relationship between gross primary productivity (GPP) and net primary productivity (NPP) is not fully understood. One of the uncertainties relevant to this issue is the magnitude of woody tissue respiration. Although some data exist for temperate and boreal zones, measurements of woody tissue respiration in tropical forests are sparse. We made in situ chamber measurements of woody tissue respiration in two tropical rain forests, one in the Brazilian Amazon (Reserva Jarú) and one in Central Cameroon (Mbalmayo Reserve). We made measurements on a wide range of species at each site and over a range of stem diameters from 0·02 to 1·4 m. The rate of efflux of carbon dioxide (CO2) from bark at 25 °C, Rt, varied from 0·1 to 5·2 µmol m−2 s−1 across the two sites, and the efflux was related to both volume and surface area components of the measured stem sections. The temperature response in Rt was slightly higher at Jarú than at Mbalmayo, with Q10 values of 1·8 (± 0·1 SE) and 1·6 (± 0·1 SE), respectively. A log–log regression showed that Rt was significantly related to stem diameter, D (P < 0·001; r2 = 0·58–0·62) and was significantly higher at Mbalmayo than at Jarú (P < 0·001), but that the rate of increase in Rt with stem diameter, D, was similar between sites. At the Mbalmayo site, tree growth measurements made over a 4 month period were used to make two estimates of the maintenance (Rm) and construction (Rc) components of respiration embedded in Rt. The two methods agreed closely, suggesting that Rm was approximately 80% of Rc at this site. Rm could be strongly related to D using a sigmoidal relationship that described both surface area and volume components as sources of respiratory CO2 (r2 = 0·71). This functional model was combined with inventory, growth and climate data for the Mbalmayo site to make a first estimate of annual above‐ground woody tissue respiration, RA, which was 257 (± 18 SE) g C m−2 year−1. This value corresponds to approximately 10% of GPP, slightly lower than that found for another tropical rain forest, but higher than for temperate forests. When combined with data from six other sites in tropical, temperate and boreal settings, a very strong relationship was found between RA and leaf area index (LAI), and between RA/GPP and LAI (P < 0·001, r2 = 0·98). This indicates that RA exerts an appreciable constraint on NPP and that this constraint varies closely with LAI across widely differing types of woody vegetation.
Effect of soil temperature on disease development in melon plants infected by Monosporascus cannonballus
Authors: Pivonia S. , Cohen R. , Kigel J. , Katan J. 
Published: March 2003

The effect of soil temperature on melon collapse induced by Monosporascus cannonballus was studied in the laboratory and in the field. In the laboratory, ascospore germination and hyphal penetration into melon roots were enhanced by increasing the temperature from 20 to 32°C. The optimum temperature for mycelial growth of five isolates of M. cannonballus was 30°C. In the field, the effect of temperature was studied in experiments conducted during the winter and autumn cropping seasons from 1995 to 1998. Disease progress was much faster in the autumn than in the winter crop seasons. Disease incidence reached 100% in the three consecutive autumn seasons studied. In the winter seasons, however, planting date influenced disease incidence. Early planting, at the beginning of January, resulted in a low disease incidence (6–26%, 125 days after planting), whereas planting at the end of January resulted in higher disease incidence (72–88%, 95–119 days after planting). In plots in which the soil was artificially heated to 35°C during the winter season, disease incidence reached 85%, as in the autumn season. Plants grown during the winter in unheated soil, or in artificially heated soil disinfected with methyl bromide, did not collapse. Root colonization by the pathogen was higher in the autumn and in heated soil than in the winter season in nonheated soil. Fifty per cent of root segments were colonized 35, 42 and 67 days after planting in the winter‐heated, autumn and winter‐unheated plots, respectively. A high correlation was found between soil temperatures above 20°C during the first 30 days after planting and disease severity. It is suggested that soil temperature during the early stages of plant development is an important factor in disease development and the expression of melon collapse caused by M. cannonballus.
Human Autologous Monocytes and Monocyte‐Derived Macrophages in Co‐Culture with Carcinoma F‐Spheroids Secrete IL‐6 by aNon‐CD14‐Dependent Pathway
Authors: Heimdal J.‐H. , Aarstad H. J. , Olsnes C. , Olofsson J. 
Published: March 2003

The secretion of interleukin (IL)‐1β, IL‐6 and tumour necrosis factor (TNF)‐α were compared when freshly isolated autologous monocytes or monocytederived macrophages (MDMs) were co‐cultured in vitro with autologous fragment (F)‐spheroids established from a series of head and neck squamous cell carcinoma (HNSCC) patients. F‐spheroids were generated from the malignant tumour (M‐spheroids) or from benign mucosa (B‐spheroids) from which the tumour originated control. If monocytes maturated towards MDMs before co‐culture, the IL‐6 secretion declined dependent on the extent of the MDM maturation by both M‐ and B‐spheroid stimulation. When MDMs maturated in continuous co‐culture, a steady‐state secretion of IL‐6 continued for several days but diminished when the culture medium was changed every 24 h. No co‐culture‐induced IL‐1β or TNF‐α was determined. Both the cytokine secretion and the mRNA gene expression revealed a different monocyte/MDM activation when co‐culture and lipopolysaccharide (LPS)‐stimulation were compared. Addition of anti‐CD14 (10 µg/ml) decreased monocyte LPS‐stimulated, but increased monocyte co‐culture stimulated IL‐6 secretion. In conclusion, M‐ and B‐spheroids similarly stimulated monocytes and to a lesser extent MDMs. MDMs that maturated with F‐spheroids present, retained responsiveness at the monocyte level. Co‐culture‐induced monocyte stimulation, as measured by IL‐6 secretion, was not dependent on activation via the CD14 molecule.
Origin of Dinantian zebra dolomites south of the Brabant‐Wales Massif, Belgium
Authors: NIELSEN P. , SWENNEN R. , MUCHEZ PH. , KEPPENS E. 
Published: March 2003

Zebra dolomites, characterized by a repetition of dark grey (a) and light (b) coloured dolomite sheets building up abbabba‐sequences, occur in Dinantian strata from deep boreholes (> 2000 m) south of the Brabant‐Wales Massif in Belgium. These zebra dolomite sequences are several tens of metres thick. The dark grey dolomite sheets (a) consist of non‐planar crystals, 80–150 μm in diameter. These crystals display a mottled red–orange luminescence and are interpreted to be replacive in origin. The white dolomite sheets (b) consist of coarse crystalline nonplanar b1 dolomite, which evolves outwards into transparent saddle shaped b2 dolomite. The b1 dolomites possess a mottled red–orange luminescence similar to the a dolomites, while the saddle shaped b2 rims display red to dark brown luminescent‐zones. The b1 dolomites are possibly partly replacive and partly cavity filling. Their b2 rims display criteria typical for a cement origin. Locally, cavities exist between two succeeding white dolomite sheets. These cavities make up ≈5% of the zebra rocks and are locally filled by saddle shaped ankerite and/or xenomorphic ferroan calcite.Geochemical and fluid inclusion data (Th ≈ 120 °C) indicate a burial diagenetic origin for these zebra dolomites. The a and b1 dolomites are characterized by similar geochemical compositions and fluid inclusion data pointing toward a related origin. To explain the development of the zebra textures, suprahydrostatic pressures in conjunction with late Variscan tectonic compression are invoked. A model involving dolomitizing fluids expelled during the Variscan orogeny is proposed. An overpressured system is also invoked to explain the important porosity development, the creation of centimetre‐scale subvertical displacements of the zebra pattern and the microfractures affecting the b1–b2 dolomite crystals.
Preservation of cross‐sets due to migration of current ripples over aggrading and non‐aggrading beds: comparison of experimental data with theory
Authors: Storms Joep E. A. , Dam Remke L. Van , Leclair Suzanne F. 
Published: March 2003

An experimental study of the preservation of cross‐sets during the migration of current ripples under aggrading and non‐aggrading conditions was conducted in order to test the modified Paola–Borgman theory for distribution of cross‐set thickness as a function of distribution of bed‐wave height. In a series of flume experiments, the geometry and migration characteristics of the ripples did not vary systematically with aggradation rate and are comparable to other flume and river data.Mean cross‐set thickness/mean formative bed‐wave height is less than 0·4, and mean cross‐set thickness/mean bed‐wave height is less than 0·53. In the present experiments, the primary control of cross‐set thickness is the variability of ripple height. Aggradation rate accounts for only 1–7% of the total cross‐set thickness.A two‐parameter gamma density function was fitted to histograms of ripple height to determine the value of parameter a needed for the modified Paola–Borgman model. This model underestimates cross‐set thickness because of its assumption that bed‐form height spreads evenly above and below the mean bed level, which is not the case in reality. Mean cross‐set thickness is predicted quite well if the model constant is increased to 1·3.
Deposition and early alteration of evaporites
Authors: Schreiber B. Charlotte , Tabakh Mohamed El 
Published: March 2003

SummaryThe depositional settings for primary and early diagenetic evaporite deposits generally fall into three categories: marginal (mixed shallow‐subaqueous and subaerial), shallow and deep subaqueous. These three environmental groupings hold for both marine and nonmarine settings, although the details of continental evaporites may be far more complex than in most marine‐fed water bodies. The primary evaporite morphologies from many continental (playa), hypersaline marine and marine‐marginal depositional settings are reasonably well understood, because of the numerous detailed studies of recent, Holocene and Cenozoic deposits that serve as models for sedimentary interpretation. The sedimentological features that develop in deeper water settings are inferred, based on examination of unaltered Cenozoic deposits. Each environmental setting develops characteristic depositional features and patterns, and one facies grades into the next. Because there may be significant physiochemical changes in water composition during deposition as well as sudden change(s) in both water depth and basinal circulation, description and interpretation of evaporative rocks should not be based on mineralogy alone, but on the distinct sedimentary characteristics of each part of a deposit. In cases where sediments still reflect their primary mineralogy and morphology, most of the environments can now be recognized; however, geochemical studies are commonly required to determine the source(s) of the original water. The determinative geochemical techniques that presently serve as a support to sedimentologic study include studies of fluid inclusions, bromine content of chloride salts, and the stable isotopes of strontium, sulphur, carbon and oxygen. Only after these and perhaps other chemical analyses are considered can the full depositional history of a region be reasonably unravelled.
Redescription and re‐evaluation of the Burmese amber psychodid Eophlebotomus connectens Cockerell and its phylogenetic position (Diptera: Psychodidae)
Authors: Duckhouse D. A. 
Published: March 2003

Summary Eophlebotomus is re‐examined, with the discovery of important new features and colleagues that were inaccurately described by previous workers. Hennig's scheme deriving the venation of Horaiella from that of Eophlebotomus could equally well have used a trichomyiine or a sycoracine as the starting point and therefore does not specifically support the hypothesis that Horaiella is the sister group. The phlebotomine‐like features of Eophlebotomus are plesiomorphies mostly also occurring in Sycoracinae, but there are also several synapomorphies supporting a particular relationship between Eophlebotomus and Sycoracinae or Trichomyiinae or both. It is hypothesized that Eophlebotomus represents a basal offshoot of the lineage leading to Sycoracinae and Trichomyiinae.