bluuebunny/crossref_metadata_2025 huggingface dataset:
Photosynthetic responses to temperature of phosphoenolpyruvate carboxykinase type C4 species differing in cold sensitivity
Authors: MATSUBA K. , IMAIZUMI N. , KANEKO S. , SAMEJIMA M. , OHSUGI R.
Published: November 2003

Photosynthetic rates, the activities of key enzymes associated with the C4 cycle and ribulose‐1,5‐bisphosphate carboxylase (RuBPCase), and the levels of metabolites involved in the C4 cycle were compared between the two phosphoenolpyruvate carboxykinase (PCK) type C4 species Spartina anglica, which is cold‐tolerant, and Zoysia japonica, which is cold‐sensitive, during exposure to low temperature. Plants of both species grown outside in summer were placed in a growth chamber at 27/20 °C day/night temperatures. After 1 week, plants were exposed to 20/17 °C for 1 week and then to 10/7 °C for 2 weeks. Photosynthetic rates in Z. japonica decreased progressively to about 25% during the chilling treatments. In contrast, S. anglica exhibited a 43% increase in photosynthetic rates after exposure to 20 °C for 1 week, which remained relatively constant thereafter. Consistent with these observations, most of the C4 enzymes and RuBPCase in Z. japonica declined. Phosphoenolpyruvate carboxylase (PEPC) and PCK activities declined particularly drastically during the treatments. However, the activities of these enzymes in S. anglica showed either a slight increase or decrease upon a mild cold treatment, and remained relatively constant during further chilling treatments. There was a sharp decline in phosphoenolpyruvate in Z. japonica after exposure to 10 °C. On the other hand, metabolite levels in S. anglica were largely unaffected by the chilling treatments. These results suggest that the drastic declines of both PEPC and PCK activities may be important limiting factors responsible for cold sensitivity in C4 photosynthesis of Z. japonica.
Effects of carbon dioxide concentration on the interactive effects of temperature and water vapour on stomatal conductance in soybean
Authors: WILSON K. B. , BUNCE J. A.
Published: November 2003

Soybeans were grown at three CO2 concentrations in outdoor growth chambers and at two concentrations in controlled‐environment growth chambers to investigate the interactive effects of CO2, temperature and leaf‐to‐air vapour pressure difference (LAVPD) on stomatal conductance. The decline in stomatal conductance with CO2 was a function of both leaf temperature and LAVPD. In the field measurements, stomatal conductance was more sensitive to LAVPD at low CO2 at 30 °C but not at 35 °C. There was also a direct increase in conductance with temperature, which was greater at the two elevated carbon dioxide concentrations. Environmental growth chamber results showed that the relative stomatal sensitivity to LAVPD decreased with both leaf temperature and CO2. Measurements in the environmental growth chamber were also performed at the opposing CO2, and these experiments indicate that the stomatal sensitivity to LAVPD was determined more by growth CO2 than by measurement CO2. Two models that describe stomatal responses to LAVPD were compared with the outdoor data to evaluate whether these models described adequately the interactive effects of CO2, LAVPD and temperature.
Growth and water‐use efficiency of 10 Triticum aestivum cultivars at different water availability in relation to allocation of biomass
Authors: VAN DEN BOOGAARD R. , ALEWIJNSE D. , VENEKLAAS E. J. , LAMBERS H.
Published: November 2003

In environments where the amount of water is limiting growth, water‐use efficiency (biomass production per unit water use) is an important trait. We studied the relationships of plant growth and water use efficiency with the pattern of biomass allocation, using 10 wheat cultivars, grown at two soil moisture levels in a growth chamber. Allocation pattern and relative growth rate were not correlated, whereas allocation pattern and water use efficiency were. Variation in transpiration per plant resulted from variation in the rate of transpiration per unit leaf area or root weight, rather than from differences in leaf area or root weight per plant. Transpiration per unit leaf area or root weight was lower when the leaf area or root weight per unit plant weight was larger. Also, the efficiency of water use at the plant and leaf levels was higher for plants with a higher leaf area per unit plant weight, and it was not correlated with the plant's growth rate. Differences in water‐use efficiency at the leaf level were related to variation in stomatal conductance, rather than in the rate of photosynthesis. A high photosynthetic water‐use efficiency was associated with a low efficiency of nitrogen use for photosynthesis.
Evidence that inducible C4‐type photosynthesis is a chloroplastic CO2‐concentrating mechanism in Hydrilla, a submersed monocot
Authors: REISKIND J. B. , MADSEN T. V. , VAN GINKEL L. C. , BOWES G.
Published: November 2003

Hydrilla verticillata (L.f.) Royle exhibits an inducible C4‐type photosynthetic cycle, but lacks Kranz anatomy. Leaves in the C4‐type state (but not C3‐type) contained up to 5‐fold higher internal dissolved inorganic carbon (DIC) concentrations than the medium, indicating that they possessed a CO2‐concentrating mechanism (CCM). Several lines of evidence indicated that the chloroplast was the likely site of CO2 generation. From C4‐type leaf [DIC] measurements, the estimated chloroplastic free [CO2] was 400 mmol m−3. This gave a calculated 2% O2 inhibition of photosynthesis, which was identical to the measured value, and provided independent evidence that the estimated [CO2] was close to the true value. A homogeneous distribution of DIC in the C4‐type leaf could not account for such a high [CO2], or the resultant low O2 inhibition. For C3‐type leaves the estimated chloroplastic [CO2] was only 7 mmol m−3, which gave high, and similar, calculated and measured O2 inhibition values of 22 and 26%, respectively. The CCM did not appear to be located at the plasma membrane, as it operated at low and high pH, indicating that it was independent of use of HCO3− from the medium. Also, both C3− and C4‐type Hydrilla leaves showed pH polarity in the light, with abaxial and adaxial boundary layer values of about pH 4·0 and 10·5, respectively. Thus, pH polarity was not a direct component of the CCM, though it probably improved access to HCO3. Additionally, iodoacetamide and methyl viologen greatly reduced abaxial acidification, but not the steady‐state CCM. Inhibitor studies suggested that the CCM required photosynthetically generated ATP, but Calvin cycle activity was not essential. Both leaf types accumulated DIC in the dark by an ATP‐requiring process, possibly respiration, and C4‐type leaves fixed CO2 at 11·8% of the light rate. The operation of a CCM to minimize photorespiration, and the ability to recapture respiratory CO2 at night, would conserve DIC in a densely vegetated lake environment where daytime [CO2] is severely limiting, while [O2] and temperatures are high.
Effects of NO3−, NH4+ and urea nutrition on endogenous levels of IAA and four cytokinins in two epiphytic bromeliads
Authors: MERCIER H. , KERBAUY G.B. , SOTTA B. , MIGINIAC E.
Published: November 2003

The long‐term effects of different nitrogen sources on the endogenous IAA and cytokinin levels in two bromeliad species were investigated. In nature, Vriesea philippocoburgii is a tank‐forming epiphytic bromeliad which uses the tank water reservoir as a substitute for soil, whereas Tillandsia pohliana is a tankless atmospheric epiphytic species. A culture was established from seeds germinated in aseptic condictions, and the plantlets were grown for 6 months in a modified Knudson medium to which was added 8 mol m−3 of nitrogen in the form of NO3−, NH4+ or urea. The hormonal contents of the bromeliad shoots were determined by means of high‐performance liquid chromatography (HPLC), coupled to an enzyme‐linked immunosorbent assay (ELISA) for indole‐3‐acetic acid (IAA), isopentenyladenine (iP), isopentenyladenosine ([9R]iP), zeatin (Z) and zeatin riboside ([9R]Z). Nitrogen supplied in the form of urea gave the highest values of fresh and dry weights for both species, and this was positively correlated to IAA levels. The cytokinin patterns showed that isopentenyladenosine was the predominant form for both species in all samples. However, urea induced the highest level of this riboside form and also the highest level of total cytokinins for V. philippocoburgii, while NH4+ had the same effect on the atmospheric species. These results are discussed in terms of the different growth habits of these two species in nature. It is suggested that urea may be an important source of nitrogen often found inside the tank of V. philippocoburgii. NO3− treatment increased the IAA/Cks balance, mainly for V. philippocoburgii, while urea and NH4+ shifted this ratio in favour of cytokinins, thus apparently inhibiting root development in both species.
Protoplast hexose carrier activity is a determinate of genotypic difference in hexose storage in tomato fruit
Authors: RUAN Y.‐L. , PATRICK J.W. , BRADY C.
Published: November 2003

Post‐phloem sugar transport in developing tomato (Lycopersicon esculentum Mill. cv. Flora‐Dade) fruit follows an apoplastic route during the rapid phase of sugar accumulation. The pathway is characterized by sugar retrieval by the storage parenchyma cells from the fruit apoplast. Two tomato genotypes differing in fruit hexose content were compared in terms of the transport and transfer processes controlling fruit sugar levels. The genotypic difference in fruit sugar content was independent of photoassimilate export from source leaves. Discs of pericarp tissue were cultured in a medium based on analyses of the fruit apoplastic sap. The cultured discs maintained a composition, a relative growth rate and a respiration rate similar to those of the pericarp tissue of intact fruit. Estimates of hexose fluxes into metabolic and storage pools suggested that membrane transport regulated the genotypic difference in hexose accumulation. Short‐term [14C]hexose uptake experiments demonstrated a genotypic difference in Vmax for glucose, fructose and 3‐O‐methyl‐glucose, and this difference was abolished in the presence of the inhibitor p‐chloromercuribenzenesulphonic acid (PCMBS). The results support the hypothesis that the activity of energized hexose carriers on the plasma membranes of storage parenchyma cells is a significant determinate of the genotypic difference in hexose accumulation.
Stomatal responses to changes in air humidity are not necessarily linked to nocturnal CO2 uptake in the CAM plant Plectranthus marrubioides Benth. (Lamiaceae)
Authors: HERPPICH W. B.
Published: November 2003

Plants of the crassulacean acid metabolism (CAM) species Plectranthus marrubioides (Lamiaceae) were subjected to short‐ and long‐term changes in air humidity in controlled‐environment experiments. Stomata of well‐watered individuals of this all‐cell leaf‐succulent taxon responded directly, quickly and reversibly to variations of the water vapour gradient between leaf and air (Δw). Mean night‐time leaf conductance to water vapour decreased curvilinearly with increasing Δw but linearly with lowered relative air humidity. Stomatal response was generally independent of the prevailing temperature and was not linked to CO2 uptake rates. Therefore, net night‐time carbon gain, nocturnal malic acid accumulation and, thus, relative carbon recycling were not influenced by changes in air humidity in the temperature range tested. Mean nocturnal molar water use efficiency, however, decreased with decreasing air humidity because of the increased transpirational water loss. If watering was repeatedly withheld for several days during the experiments, employing a temperature regime of 35/30°C day and night, stomatal conductance became low enough to inhibit CO2 uptake, but only at the highest Δw. The results suggest that drought stress was necessary to increase responsiveness of plants to the point where CAM was also inhibited by decreases in air humidity.
EPR evidence for superoxide anion formation in leaves during exposure to low levels of ozone
Authors: RUNECKLES V. C. , VAARTNOU M.
Published: November 2003

Although the superoxide anion radical (O) has been implicated in the phytotoxicity of ozone, (O3), its role has been inferred from indirect evidence based on the activity of oxyradical scavenging systems in the leaf, particularly superoxide dismutase (SOD). Direct observations of radical signals obtained by electron paramagnetic resonance spectrometry (EPR) of intact, attached leaves of bluegrass (Poa pratensis L.) and ryegrass (Lolium perenne L.) and leaf pieces of radish (Raphanus sativus L.) during exposure to 240 μg m−3 O3 in air flowing through the spectrometer cavity have revealed the appearance of a signal with the characteristics of O. The exposures used were insufficient to cause any necrotic injury to the leaves. The appearance of the signal is light‐dependent, suggesting that it originates in the chloroplast, and its appearance is reduced in leaves in which the apoplastic pool of ascorbic acid has been enriched by prior vacuum infiltration. In each species, the signal only appeared after about 1 h of exposure to O3, and then increased steadily over the next 4 h. The lability of the species responsible for the signal is such that it can no longer be reliably detected about 15 min after cessation of the exposure to O3. These observations are interpreted as indicating that apoplastic ascorbate initially reduces the production of O, probably by reducing the penetration of O3 into the cell, with any O produced being scavenged by the chloroplastic SOD‐per‐oxidase system, but its formation from O3 then begins to exceed the capacity of the scavenging systems to remove it.
Fluxes of carbon, water and energy over Brazilian cerrado: an analysis using eddy covariance and stable isotopes
Authors: MIRANDA A. C. , MIRANDA H. S. , LLOYD J. , GRACE J. , FRANCEY R. J. , MCINTYRE J. A. , MEIR P. , RIGGAN P. , LOCKWOOD R. , BRASS J.
Published: November 2003

We present the energy and mass balance of cerrado sensu stricto (a Brazilian form of savanna), in which a mixture of shrubs, trees and grasses forms a vegetation with a leaf area index of 1·0 in the wet season and 0·4 in the dry season. In the wet season the available energy was equally dissipated between sensible heat and evaporation, but in the dry season at high irradiance the sensible heat greatly exceeded evaporation. Ecosystem surface conductance gs in the wet season rose abruptly to 0·3 mol m−2 s−1 and fell gradually as the day progressed. Much of the total variation in gs was associated with variation in the leaf‐to‐air vapour pressure deficit of water and the solar irradiance. In the dry season the maximal gs values were only 0·1 mol m−2 s−1. Maximal net ecosystem fluxes of CO2 in the wet and dry season were –10 and –15 μmol CO2 m−2 s−1, respectively (sign convention: negative denotes fluxes from atmosphere to vegetation). The canopy was well coupled to the atmosphere, and there was rarely a significant build‐up of respiratory CO2 during the night. For observations in the wet season, the vegetation was a carbon dioxide sink, of maximal strength 0·15 mol m−2 d−1. However, it was a source of carbon dioxide for a brief period at the height of the dry season. Leaf carbon isotopic composition showed all the grasses except for one species to be C4, and all the palms and woody plants to be C3. The CO2 coming from the soil had an isotopic composition that suggested 40% of it was of C4 origin.
Is glycine betaine a non‐compatible solute in higher plants that do not accumulate it?
Authors: GIBON Y. , BESSIERES M. A. , LARHER F.
Published: November 2003

Rape (Brassica napus L. var. oleifera cv. Samourai) leaf discs treated in vitro in the presence of glycine betaine (GB) exhibited very high accumulation of GB, suggesting the operation of a specific uptake system. When further subjected to osmotic upshocks by transfer to PEG 6000 media, the typical osmo‐induced proline response of the discs was strongly inhibited. The level of this inhibition was quantitatively related to the amount of GB loaded in the tissues. In contrast, the soluble sugar content increased in GB‐treated discs. Surprisingly, viability tests (i.e. membrane stability and 2,3,5‐triphenyltetrazolium chloride reduction) indicated a destabilizing effect of GB in these tissues. This is at variance with the relative compatibility of sucrose and proline. In addition, the protein content was lower in GB‐treated discs. This could be related to an inhibitory effect on protein synthesis, as demonstrated by radiolabelling of polypeptides with [35S] amino acids. This effect was particularly pronounced on Rubisco large sub‐unit synthesis and was still apparent under non‐stress conditions. The GB treatment was also followed by the induction or up‐regulation of a set of polypeptides, not seen under stress conditions, while the synthesis of osmo‐induced polypeptides was not affected by GB. These novel effects of GB lead us to discuss the reasons for its incompatibility in leaf tissues of a non‐GB‐accumulating species.
Potato plants contain multiple forms of sucrose phosphate synthase, which differ in their tissue distributions, their levels during development, and their responses to low temperature
Authors: REIMHOLZ R. , GEIGER M. , HAAKE V. , DEITING U. , KRAUSE K.‐P. , SONNEWALD U. , STITT M.
Published: November 2003

Antibodies raised against a peptide fragment (residues 60–456) of potato sucrose phosphate synthase (SPS) were used to investigate whether potato plants contain multiple forms of SPS. When a partially purified preparation of SPS from cold‐stored potato tubers was separated on 5% polyacrylamide gel electrophoresis (PAGE), four immunopositive bands were found with estimated molecular weights of 125, 127, 135 and 145 kDa. These bands were also found in rapidly prepared extracts and were termed SPS‐1a, SPS‐1b, SPS‐2 and SPS‐3, respectively. Direct evidence that SPS‐1a and SPS‐1b represent active SPS was provided by the finding that both are greatly reduced in plants expressing an antisense sequence derived from the potato leaf SPS gene. SPS‐2 was not decreased in the antisense plants, indicating that it has a significantly different sequence. Evidence that SPS‐2 represents active SPS was obtained by showing that the amount of SPS‐1a and SPS‐1b protein remaining in the leaves and tubers of antisense potato plants was too low to account for the remaining SPS activity. The four immunopositive SPS forms had different tissue distributions. SPS‐1a was the major form in all tissues except petals, sepals and stamens. SPS‐1b and SPS‐2 were absent in very young growing tissues but were present as minor forms in source leaves and sprouting tubers. The SPS‐1b level was especially high in petals and sepals, and the SPS‐2 level was especially high in the stamens. SPS‐3 was only detected in very young tissues. The four forms also showed different responses to low temperature. Transfer of tubers to 4°C led to a specific and reversible increase of SPS‐1b during the next 4 d. The appearance of SPS‐1b correlated with a change in the kinetic properties of SPS that has recently been shown (Hill et al. 1996) to play a key role in triggering the accumulation of sugars in cold‐stored tubers. The appearance of SPS‐1b protein at low temperature was accompanied by an increase of SPS transcript. Incubation of tuber slices with calyculin A and okadaic acid to alter the phosphorylation state of SPS did not lead to appearance or disappearance of SPS‐1b. It is concluded that potato plants contain several forms of SPS that have different functions in growing and mature tissues, in flower parts, and in acclimation to low temperature.
Regulation of Rubisco by inhibitors in the light
Authors: PARRY M. A. J. , ANDRALOJC P. J. , PARMAR S. , KEYS A. J. , HABASH D. , PAUL M. J. , ALRED R. , QUICK W. P. , SERVAITES J. C.
Published: November 2003

2‐carboxy‐D‐arabinitol‐1‐phosphate (CA1P) bound to Rubisco either in leaf extracts or after purification can be displaced by SO42− ions. Thus, treatment of leaf extracts with a buffer containing 200 mol m−3 SO42− displaces any bound CA1P and enables measurement of maximum car‐boxylation potential. In tobacco leaves, the activity following treatment with SO4−2 ions (‘maximal activity’) is greater than the total Rubisco activity. The ratio of the two activities altered in a dynamic way with fluctuations in irradiance. Even in species which do not produce significant amounts of CA1P, the maximal activity greatly exceeded the total activity. Anion exchange separation of components in acid extracts confirmed the absence of CA1P in tobacco leaves harvested above an irradiance of 300 μmol quanta m−2 s−1, but the presence of another inhibitor of Rubisco. These results are consistent with the regulation of Rubisco activity by inhibitors other than CA1P which, like CA1P, can be displaced by SO42− ions.
Striga hermonthica reduces photosynthesis in sorghum: the importance of stomatal limitations and a potential role for ABA?
Authors: FROST D. L. , GURNEY A. L. , PRESS M. C. , SCHOLES J. D.
Published: November 2003

We report the effects of the root hemiparasite Striga hermonthica (Del.) Benth. on the growth and photosynthesis of two cultivars of sorghum: CSH‐1, a susceptible variety, and Ochuti, which shows some tolerance to S. hermonthica in the field. Within 4 d of parasite attachment to the host roots, infected plants of both cultivars were significantly shorter than uninfected controls. At 55 d, infected plants of both cultivars had significantly less shoot and root biomass, and significantly smaller leaf areas than uninfected controls. The dry weight of S. hermonthica attached to host roots was insufficient at this stage to explain the decreased growth in terms of a competing sink for carbon and nitrogen. Leaf chlorophyll and nitrogen per unit area were greater in infected plants of both cultivars compared with control plants. However, whereas photosynthesis and transpiration in young leaves of infected CSH‐1 plants declined with time when compared with controls, the rates in infected Ochuti plants were similar to those in uninfected controls throughout the time course of observation. In both cultivars, a strong correlation was observed between the rate of photosynthesis and stomatal conductance during photosynthetic induction, but infection resulted in a much slower induction than in controls. In CSH‐1 plants, both steady‐state photosynthesis and stomatal conductance were lower than in controls, whereas in leaves of Ochuti steady‐state photosynthesis and stomatal conductance eventually reached the same values as in the control leaves. Results from AlCi analysis and also from determination of 13C isotope discrimination were consistent with a stomatal limitation to photosynthesis in the leaves of Striga‐infected plants. The concentration of the plant growth regulator abscisic acid (ABA) was measured in the xylem sap of infected CSH‐1 plants only, and was found to be twice that of uninfected plants. A possible role of ABA in determining host response to infection by S. hermonthica is discussed.
Kinetics and relative significance of remobilized and current C and N incorporation in leaf and root growth zones of Lolium perenne after defoliation: assessment by 13C and 15N steady‐state labelling
Authors: DE VISSER R. , VIANDEN H. , SCHNYDER H.
Published: November 2003

The contribution of pre‐defoliation reserves and current assimilates to leaf and root growth was examined in Lolium perenne L. during regrowth after defoliation. Differential steady‐state labelling with 13C (CO2 with δ13C = ‐0.0281 and ‐0.0088) and 15N (NO3− with 1.0 and 0.368 atom percentage, i.e. δ15N = 1.742 and 0.0052, respectively) was applied for 2 weeks after defoliation. Rapidly growing tissues were isolated, i.e. the basal elongation and maturation zones of the most rapidly expanding leaves and young root tips, with a biomass turnover rate > 1 d−1. C and N weights of the elongation zone showed a transient decline. The dry matter and C concentration in fresh biomass of leaf growth zones transiently decreased by up to 25% 2 d after defoliation, while the N concentration remained constant. This ‘dilution’ of growth zone C indicates a decreased net influx of carbohydrates relative to growth‐related influx of water and N in expanding cells, immediately after defoliation. Recovery of the total C and N weights of the leaf elongation zone coincided with net incorporation of currently absorbed C and N, as shown by the kinetics of δ13C and atom percentage 15N in the growth zones after defoliation. C isotope discrimination (Δ13C) in leaf growth zones was about 23‰, 1–2‰ higher than the Δ in root tips. Δ15N in the leaf and root growth zones was 10±3‰. The leaf elongation zones (at 0–0.03 m from the tiller base) and the distant root tips (about 0.2 m from the base) exhibited similar kinetics of current C and N incorporation. The amount of pre‐defoliation C and N in the growth zones, expressed as a fraction of total C and N, decreased from 1.0 to 0.5 at 3 (C) and 5 (N) d after defoliation, and to 0.1 at 5 (C) and 14 (N) d after defoliation. Thus, the dependence of growth zones on current assimilate supply was significant, and stronger for C than for N. The important roles of current assimilates (as compared to pre‐defoliation reserves) and ‘dilution’ of dry matter in regrowth after defoliation are discussed in relation to the method of labelling and the functional and morphological heterogeneity of shoot tissues.
Detoxification of xenobiotics in plant cells by glutathione conjugation and vacuolar compartmentalization: a fluorescent assay using monochlorobimane
Authors: COLEMAN J. O. D. , RANDALL R. , BLAKE‐KALFF M. M. A.
Published: November 2003

Monochlorobimane (BmCl), a non‐fluorescent cell‐per‐meant compound that reacts with glutathione to yield a strong blue fluorescent conjugate bimane‐glutathione (Bm‐SG), was used to trace the glutathione‐dependent detoxification of xenobiotics in plant cells and protoplasts. In BmCl‐labelled cells and protoplasts, fluorescence developed rapidly and was quickly concentrated in the vacuole. The rate of fluorescence development was dependent on the concentration of BmCl and the only metabolite formed was the conjugate Bm‐SG. The formation of Bm‐SG was correlated with a decrease in the amount of intracellular GSH. Compounds which reduced the intracellular levels of GSH severely reduced the formation of Bm‐SG. Bm‐SG was shown to be transported into isolated vacuoles by an ATP‐dependent vana‐date‐sensitive mechanism. Kinetic analysis of cellular Bm‐SG formation implicated both spontaneous conjugation and enzyme catalysis. Our results demonstrate a cellular pathway for xenobiotic detoxification in plants, starting with conjugation to glutathione in the cytoplasm, followed by the transport of the conjugates into the vacuole. This pathway is used to counter the toxic effects of some herbicides and environmental pollutants and overlaps with or parallels the pathway used for the biosynthesis of anthocyanins.
Xylem dysfunction caused by water stress and freezing in two species of co‐occurring chaparral shrubs
Authors: LANGAN S. J. , EWERS F. W. , DAVIS S. D.
Published: November 2003

Water transport from the roots to leaves in chaparral shrubs of California occurs through xylem vessels and tracheids. The formation of gas bubbles in xylem can block water transport (gas embolism), leading to shoot dieback. Two environmental factors that cause gas embolism formation in xylem conduits are drought and freezing air temperatures. We compared the differential vulnerabilities of Rhus laurina and Ceanothus megacarpus, co‐dominant shrub species in the coastal regions of the Santa Monica Mountains of southern California, to both water stress‐induced and freezing‐induced embolism of their xylem. Rhus laurina has relatively large xylem vessel diameters, a deep root system, and a large basal burl from which it vigorously resprouts after wildfire or freezing injury. In contrast, Ceanothus megacarpus has small‐diameter vessels, a shallow root system, no basal burl and is a non‐sprouter after shoot removal by wildfire. We found that R. laurina became 50% embolized at a water stress of –3 MPa and 100% embolized by a freeze–thaw cycle at all hydration levels. In contrast, C. megacarpus became 50% embolized at a water stress of –9 MPa and 100% embolized by freeze–thaw events only at water potentials lower than –3 MPa. Reducing thaw rates from 0·8 °C min−1 to 0·08 °C min−1 (the normal thaw rate measured in situ) had no effect on embolism formation in R. laurina but significantly reduced embolism occurrence in well‐hydrated C. megacarpus (embolism reduced from 74 to 35%). These results were consistent with the theory of gas bubble formation and dissolution in xylem sap. They also agree with field observations of differential shoot dieback in these two species after a natural freeze–thaw event in the Santa Monica Mountains.
Is photomorphogenic shade avoidance adaptive? Perspectives from population biology
Authors: SCHMITT J.
Published: November 2003

Photomorphogenic shade avoidance responses provide an ideal model system for integrating genetic, physiological and population biology approaches to the study of adaptive plasticity. The adaptive plasticity hypothesis predicts that shade avoidance phenotypes induced by low ratios of red to far‐red light (R:FR) will have high relative fitness in dense stands, but will suffer a fitness disadvantage at low density. Experiments with transgenic and mutant plants in which photomorphogenic genes are disabled, as well as phenotype manipulation by means of altered R:FR, strongly support the shade avoidance hypothesis. The observation of photomorphogenic ecotypes in different selective environments also suggests that the shade avoidance response has undergone adaptive evolution. Quantitative genetic variation in R:FR sensitivity has been detected in wild populations, indicating that the evolutionary potential exists for response to natural selection. However, evolutionary response may be constrained by genetic correlations among developmentally linked traits. Therefore it cannot be assumed that an observed suite of photomorphogenic responses represents an adaptive optimum for every trait.
The COP9 complex: a link between photomorphogenesis and general developmental regulation?
Authors: CHAMOVITZ D. A. , DENG X.‐W.
Published: November 2003

Light signals perceived by photoreceptors are transduced into the nucleus to regulate gene expression and development. The COP9 protein complex localized in the nucleus has a central role in modulating light‐regulated development, and may have a role in regulating development in general in all organisms. This review considers recent advances in the study of the COP9 complex and its sub‐units in plant and animal systems, and discusses the possible functional implications.
Signal transduction in the photocontrol of chalcone synthase gene expression*
Authors: SCHÄFER E. , KUNKEL T. , FROHNMEYER H.
Published: November 2003

The photocontrol of chalcone synthase gene expression was studied by means of promoter analyses, in vitro systems, photoreceptor mutants and microinjections, and pharmacological approaches. A 52 bp element of the promoter is necessary and sufficient to transfer light regulation. Chalcone synthase expression is primarily under the control of phyA and blue/UV photo receptors; the latter are functional even in the absence of phyA and phyB. Phytochromes seem to be soluble proteins and, within seconds of irradiation, light‐dependent phosphorrylations were observed in membrane‐depleted cytosol preparations, indicating very early processes of signal transduction. Microinjection and pharmacological experiments reveal that, in the phyA pathway, heterotrimeric G‐proteins, cGMP and a genistein‐sensitive protein kinase are involved, whereas the UV pathway includes several trimeric G‐proteins and Ca/calmodulin‐dependent steps.
Gibberellins, brassinosteroids and light‐regulated development
Authors: CHORY J. , LI J.
Published: November 2003

The regulation of plant development by light requires the action of several well‐studied plant hormones. However, the mechanism by which light and hormones affect identical developmental responses remains unclear. Recently, studies of mutants altered in light signal perception or transduction have suggested a role for gibberellins and brassinosteroids in light‐regulated development. For instance, mutants in the major light‐stable phytochrome from several plant species exhibit altered responsiveness to, or metabolism of, gibberellins. In contrast, mutants that develop as light‐grown plants in the absence of light have implicated a role for brassinosteroids in the control of cell elongation, the expression of photoregulated genes, and the promotion of apical dominance, leaf senescence and male fertility. Future studies should help elucidate whether light and hormones independently affect these developmental responses or whether hormones are involved in the sequence of events initiated by excitation of photoreceptors.
Immunohistochemical analysis of procathepsin L and cathepsin B in cutaneous Kaposi's sarcoma
Authors: Thewes Matthias , Engst Reinhard , Jürgens Maren , Borelli Siegfried
Published: November 2003

Background

The expression of the proteinases cathepsins L and B are induced in tumors by malignant transformation, growth factors, and tumor promoters suggesting they play an important role in tumor invasion and metastasis.

Methods

By immunohistochemistry, procathepsin L and cathepsin B were studied in patients with Kaposi's sarcoma (KS). Formalin‐fixed and paraffin‐embedded tissues from 29 cases of KS (AIDS‐associated KS, n= 24; non‐AIDS‐associated KS, n= 5) were immunolabeled with the polyclonal antibody directed against procathepsin L and the antisera directed against cathepsin B.

Results

Normal epidermis, eccrine sweat glands, and hair follicle expressed both cathepsins. We also found a positive staining for procathepsin L in normal blood vessels. In both “angiomatous” and “fibroblastic” lesions of KS no expression of these enzymes was observed.

Conclusions

These findings support the hypothesis of a benign autochthonous origin of the lesions, such as a hyperplasia.
Onchocerciasis: clinical presentation and host parasite interactions in patients of Southern Sudan
Authors: Stingl Peter
Published: November 2003

Background

Onchocerciasis, an infection by the filarial nematode Onchoverca volvulus, is widely distributed in tropical Africa and of great dermatologic interest. This study analyses the dermatologic presentation and tries to determine the correlations between clinical disease and host parasite interactions in onchocerciasis patients of the Southern Sudan.

Methods

We performed clinical and histopathologic investigations in patients with onchocerciasis in the Wau District, Bahr el Ghazal Province, Southern Sudan. As well as a detailed clinical skin examination, skin biopsies were taken, processed, and Investigated for type and degree of host tissue response. Parasitologic, clinical, and histopathologic findings were evaluated.

Results

Onchocerciasis appears with a variety of severe skin lesions. Central is a pruritic rash. Long‐standing cases develop extensive pigmentary changes and impressive signs of skin tissue exhaustion. Cellular host tissue responses to degenerating skin microfilariae seem to play a key role in the development of skin pathology. The degree of host response appears to be inversely proportional to the host's microfilarial load.

Conclusions

Onchocerciasis represents a health problem of great dermatologic importance in Southern Sudan. The study results demonstrate clinical variations in onchocerciasis and provide support for the existence of a disease spectrum.
An outbreak of paederus dermatitis in a suburban hospital in Sri Lanka
Authors: Kamaladasa Satheeka D. , Perera W.D.H. , Weeratunge L.
Published: November 2003

Background

In a modern hospital built recently in Sri Lanka the staff members on night shifts and some patients in the open wards were known to be affected by an acute vesicating dermatitis. The study was carried out to identify the cause of the dermatitis and recommend preventive measures.

Methods

Members of the hospital staff and patients who developed an acute vesicating dermatitis over a period of 2 years were studied using a questionnaire. The clinical features, relationship to night shifts and the month of occurrence were noted. Insects were caught at night on several occasions and identified. Lesions were reproduced in volunteers.

Results

Out of a total of 124 patients studied, 108 were members of the hospital staff and it was noted that they had all been on night shifts within 2 days prior to the onset of the lesions. The insect caught belongs to class Coleoptera, family Staphylinidae, genus Paederus, and species fuscipes. The incidence was seasonal with clustering of cases seen to occur twice a year.

Conclusions

This IS an outbreak of dermatltls due to Paederus fusicipes. Awareness of the condition and its clinical features will prevent misdiagnosis and the simple preventive measures suggested are based on the behavioral pattern of this nocturnal beetle.
A distinctive vesiculopustular eruption associated with hepatobiliary disease
Authors: Magro Cynthia M. , Crowson A. Neil
Published: November 2003

Background Cutaneous manifestations of hepatobiliary disease may be a clue to the clinical diagnosis. We encountered a form of vesiculopustular eruption in five patients with hepatobiliary disease. A similar eruption has been described in the setting of ulcerative colitis, and has received the designation of vesiculopustular pyoderma gangrenosum.

Methods Skin biopsy specimens were examined by conventional histopathologic methods and, in three cases, fresh tissue was available for direct immunofluorescence examination. A diagnosis of hepatobiliary disease was known in three of the patients and in the other two it was established by the skin biopsies.

Results All skin biopsies of the five patients showed a neutrophilic dermatosis that had two morphologies. One was characterised by superficial neutrophilic dermolysis with subepidermal bulla formation and the other by a nonulcerating destructive suppurative folliculitis and perifollicular neutrophilic dermolysis. Both were frequently accompanied by a neutrophilic and lymphotic eccrine hidradermitis and a Sweet's syndrome‐like vascular reaction. The lesions were held to represent a novel vesiculopustuiar eruption with features reminiscent of pyoderma gangrenosum.

Conclusions We propose the term vesiculopustular eruption of hepatobiliary disease for this distinctive clinicopathologic entity, which bears a strong histologic resemblance to pyoderma gangrenosum. Patients with a known hepatopathy who present with necrotizing vesicles and pustules may have such an eruption. The onset may be the first clue to or herald an exacerbation of underlying liver disease.
Colchicine as a novel therapeutic agent in chronic bullous dermatosis of childhood
Authors: Banodkar Degamber D. , Al‐Suwaid Abdul Raouf
Published: November 2003

Background The treatment of chronic bullous dermatosis of childhood (CBDC) so far has been limited to the use of corticosteroids and the sulfa group of drugs, e.g. daspsone and sulfapyridine. Furthermore, the therapy of CBDC cases with associated G6 PD deficiency is restricted only to systemic steroids. Histopathologically CBDC is characterized by the presence of predominantly neutrophilic Infiltration and because it has been proven to exert strong anti‐inflammatory effects through the inhibition of neutrophils, colchicine was mandated for its use in CBDC.

Methods To avoid the detrimental side‐effects of the long‐term use of steroids in children, an alternative anti‐inflammatory drug like colchicine was considered. Patients with G6 PD deficiency and those who were not satisfactorily controlled with steroid therapy, and who in addition developed unacceptable side‐effects like cushingoid faces and hypertrichiosis, were treated with the drug.

Results Eight patients were given colchicine, five (62.5%) of which showed complete remission within 4–6 weeks of starting the therapy. The remaining three (37.5%) also responded but required adjuvant small doses of steroids to maintain the remissions. The drug was very well tolerated and no side‐effects were observed.

ConclusionsColchicine is, therefore, found to be an effective treatment in CBDC and has enhanced our armamentarium of therapeutics for this condition, especially in children with G6 PD deficiency.
Perforating granuloma annulare
Authors: Peñas Pablo F. , Jones‐Caballero María , Fraga Javier , Sánchez‐Pérez Javier , García‐Díez Amaro
Published: November 2003

Background

Perforating granuloma annulare (PGA) is considered an histologic subtype of granuloma annulare (GA) and it is described as a very rare disease, usually of children, affecting the dorsum of the hands. Mechanisms leading to perforation are unknown. Our experience suggested a different clinical presentation, so we decided to review our patients and the cases published.

Methods

We present six cases of PGA and review 52 PGA cases reported in the literature. Data regarding sex, age, time of evolution of disease, clinical features, laboratory findings, treatment, and follow‐up were collected. The significance level was determined by the χ2 or Student t test when appropriate.

Results

The prevalence of PGA could be up to 5% of GA. Pustular‐like lesions can be found in 26% of cases, and scars in 37%; papular, umbilicated, and crusted lesions being the most common finding. While PGA appears as a single lesion in only 9% of cases, and half of the patients are older than 30 years, in GA 50% of cases present as a single lesion and 80% of patients are younger than 30 years.

Conclusions

PGA is different to GA not only histologically but also clinically. It is a disseminated disease, affecting both children and adults, which is characterized by the presence of multiple papules, most of them umbilicated and/or crusted, and characteristically pustular lesions and scars. Histology suggests that the superficial localization of the necrobiotic granuloma leads to the epidermal perforation. Treatment is disappointing.
Epidemiology of primary cutaneous malignant melanoma in Jordan
Authors: Oumeish Oumeish Youssef
Published: November 2003

Background

Primary cutaneous malignant melanoma is an uncommon tumor in Jordan compared with other countries. There are no previous comprehensive Jordanian studies on this tumor and proper statistical data on morbidity and incidence are nonexistent. The purpose of this paper was to study the epidemiologic aspects of cutaneous malignant melanoma among Jordanians.

Methods

Both the clinical and the histopathologic feature of 138 melanoma patients (86 men, median age 56; 52 women, median age 53) seen during the period November 1969‐May 1994 were studied. The analysed data included age, sex, skin type, race, socioeconomic status, exposure to sunlight, trauma, and family history.

Results

Malignant melanoma was found to be more common in men than women, in the ratio of approximately 2:1, due to the higher exposure of men to sunlight, and occurred more in people with skin types I, II, and III, and less in people with skin types IV and V. The majority of cases were of the superficial spreading variety, followed by the nodular, lentigo maligna, and acrolentiginous melanomas, respectively.

Conclusion

The incidence of cutaneous malignant melanoma, formerly considered a rare tumor in Jordan, is now recognized to be on the increase. Exposure to sunlight seems to be the most prominent risk factor in the development of this tumor among Jordanians.
Nailfold capillary abnormality and pulmonary hypertension in systemic sclerosis
Authors: Ohtsuka Tsutomu , Hasegawa Akira , Nakano Akihiko , Yamakage Akio , Yamaguchi Mary , Miyachi Yoshiki
Published: November 2003

Background

Patients with systemic sclerosis (SSC) show a capillary abnormality of nailfolds with controversial correlation with organ involvement. Our purpose was to study the correlation between this nailfold capillary abnormality and pulmonary hypertension in patients with SSC.

Methods

We studied the nailfold capillaries, using capillary microscopy, and the pulmonary arterial pressure, using right‐heart catheterlzation, in 44 patients with SSC. Canonical discriminant analysis was used to define the capillary abnormality in patients with SSC, which was then compared with that of 40 normal controls. The correlations between the patterns of nailfold capillaries and the cardiopulmonary findings. Including the pulmonary arterial pressure, were examined using Fisher's test.

Results

Thirty‐two of 44 patients with SSC could be differentiated from normal controls by our definition of the SSC pattern. The SSC pattern correlated significantly with elevated pulmonary vascular resistance, as well as with pulmonary fibrosis, eiectrocardiographic abnormalities, decreased vital capacity, and decreased diffusing capacity for carbon monoxide. All SSC patients with pulmonary hypertension showed this SSC pattern. In patients with elevated pulmonary arterial pressure, capillary microscopy and diffusion capacity for carbon monoxide (DCCM) showed the highest rate of abnormalities. A limited‐type SSC significantly correlated with DCCM and with anticentromere antibody, and the diffuse‐type SSC with pulmonary fibrosis and anti‐sci‐70 antibody.

Conclusion

Our data suggest that in patients with SSC, nailfold capillary abnormalities correlate with pulmonary arterial hypertension as well as with clinical and laboratory findings indicating pulmonary hypertension.
Toxic epidermal necrolysis – a retrospective study
Authors: Criton S. , Devi K. , Sridevi P.K. , Asokan P.U.
Published: November 2003

Background Toxic epidermal necrolysis (TEN) is a severe, idiosyncratic, exfoliative disease of the skin and mucous membranes. The treatment of this condition is controversial. High‐dose corticosteroid therapy has been the most commonly advocated treatment, but, more recently, this has changed to a no‐steroid protocol. These conflicting treatments prompted us to evaluate retrospectively our protocol.

Methods The patients admitted to the hospital from 1989 to 1995 with a clinical diagnosis of TEN were included in the study. These patients were given systemic steroids, prophylactic antibiotic, and supportive measures.

Results The patients belonged to both sexes with an average age of 34 years. The average area of involvement was 85.62%. All the patients made an uneventful recovery without any evidence of sepsis.

Conclusions Treatment with systemic steroids is useful in the management of TEN, and there is no need for a burn care center.
Complications of 585‐nm pulsed dye laser therapy
Authors: Boixeda Pablo , Núñez Mariía , Pérez Bibiana , de las Heras María Elena , Hilara Yolanda , Ledo Antonio
Published: November 2003

Background

Port‐wine stains (PWS) are a congenital, progressive ectasia of the superficial cutaneous vascular plexus that occur in 0.3%–0.5% of children at birth. They should be considered a disease with physical and psychologic complications. Treatment with the flashlamp pulsed dye laser (FPDL) has proven to be effective. Because treatment results in selective vascular injury, the risk of complications is minimal. The purpose of this study was to determine the cutaneous side‐effects and complications and their frequency in patients with PWS treated with the FPDL. Eighty‐nine patients who had been treated with the FPDL for PWS were included in this study.

Methods

Patients were treated at 3‐month intervals using slightly overlapping pulses with fluences of 6.0–9.0 J/cm2. Treating physicians were responsible for evaluating the patients. All patients were reviewed and side‐effects and complications were recorded.

Results

Pigmentary changes were the most frequently observed complications. Hyper‐and hypopigmentation appeared in 16.8% and 2.4% of patients, respectively. Cutaneous depressions occurred in 2.2% of patients. One patient developed a hypertrophic scar, and another patient presented with transient cutaneous pustulosis. All these changes usually resolved spontaneously and completely in a few months.

Conclusions

Most of the side‐effects and complications produced by the FPDL are usually transitory, and it is essentially a very secure technique.