bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microclimate above grass adversely affects spring growth of seedling snow gum (Eucalyptus pauciflora)
Authors: BALL M. C. , EGERTON J. J. G. , LEUNING R. , CUNNINGHAM R. B. , DUNNE P. 
Published: November 2003

ABSTRACTGrowth of snow gum seedlings (Eucalyptus pauciflora Sieb. ex Spreng.) was studied in response to differences in microclimate caused by differential heat exchange between seedlings, grass and bare, moist soil during winter and spring. Seedlings were planted in a pasture either directly into grassy groundcover or in circular patches of bare soil of 30, 60 or 120 cm in diameter. There were no differences in maximum air temperatures at seedling leaf height between treatments. However, minimum air temperature increased by 2 °C with increase in patch diameter from 0 to 120 cm such that seedlings surrounded by grass experienced lower minimum temperatures with more frequent and more severe frosts than seedlings growing in large patches of bare soil. These small‐scale differences in minimum temperature affected both photosynthetic and growth processes. Over winter, seedlings were photoinhibited, with depression in midday Fv/Fm linearly related to minimum temperatures. In spring, repeated frosts and lower minimum temperatures led to a delay in the recovery of Fv/Fm, a delay in bud‐break, damage to elongating stems and developing leaves, lower rates of stem elongation, and ultimately a shorter growing season for seedlings in grass compared to those in bare soil patches. Thus, microclimate above grass adversely affects spring growth of juvenile Eucalyptus pauciflora and may account for much of the competitive inhibition of tree seedling growth by grass during spring.
Virus‐induced differences in the response of oat plants to elevated carbon dioxide
Authors: MALMSTRÖM C. M. , FIELD C. B. 
Published: November 2003

ABSTRACTDisease is an integral element of agricultural and natural systems, but the roles pathogens play in determining ecosystem response to elevated CO2 have rarely been examined. To investigate whether disease can alter the response of plants to CO2, we examined the effects of doubled CO2 (∼700 μmol mol−1) on Avena sativa infected with barley yellow dwarf virus (BYDV), a common pathogen of cereals and grasses. Oats infected with BYDV showed a significantly greater biomass response to CO2 enrichment than did healthy plants. Root mass of diseased plants increased by 37–60% with CO2 enrichment, but was largely unaffected in healthy plants. CO2 enrichment increased midday leaf‐level photosynthesis and instantaneous water use efficiency by 34 and 93% in healthy plants and by 48 and 174% in infected plants. Foliar carbohydrates increased with both CO2 enrichment and BYDV infection, but the two factors affected individual pools dissimilarly. CO2 enrichment may alter the epidemiology of BYDV by increasing the persistence of infected plants.
The combined effects of CO2 concentration and solar UV‐B radiation on faba bean grown in open‐top chambers
Authors: VISSER A. J. , TOSSERAMS M. , GROEN M. W. , MAGENDANS G. W. H. , ROZEMA J. 
Published: November 2003

ABSTRACTThe response of faba bean seedlings to the combined effects of increased atmospheric CO2 concentrations ([CO2]) and solar UV‐B irradiance was studied using open‐top chambers transparent to UV‐B radiation. The purpose of the study was to determine whether effects of increased [CO2] on growth and physiology are modified by the present solar UV‐B fluence rate in the Netherlands. Seedlings were exposed to 350 or 700 μmol mol−1 CO2. At both [CO2], solar UV‐B irradiance was either present or reduced using polyester foil opaque to UV‐B radiation. To obtain information on the time dependence of increased [CO2] and UV‐B radiation effects, three harvests were performed during the experiment. CO2 enrichment resulted in increased biomass production at all harvests. At the final harvest, UV‐B radiation did not affect biomass production but a significant decrease was observed after 14 d of treatment. A reduction of the UV‐B fluence increased shoot length at both [CO2] throughout the experiment. UV‐B radiation slightly altered biomass allocation. Plants grown at reduced levels of UV‐B radiation invested less biomass in flowers and more in stem material compared to plants grown at ambient UV‐B levels. CO2 enrichment resulted in a stimulation of net photosynthesis after 26 and 38 d of treatment. UV‐B reduction did not alter this response. After 26 d of treatment, photosynthetic acclimation to CO2 enrichment was observed, which was probably the result of accumulation of carbohydrates in the leaves. After 38 d, photosynthetic acclimation was no longer present. The UV absorbance of methanolic leaf extracts was increased by CO2 enrichment only. Both CO2 enrichment and solar UV‐B reduced the transmittance of radiation through intact attached leaves. Interaction between [CO2] and UV‐B radiation was limited to UV‐A transmittance of leaves. Under prevalent experimental conditions, UV‐B radiation did not affect the measured physiological parameters. Most open‐top chambers used for climate change research are constructed of materials which do not transmit UV‐B radiation. Our results indicate that part of the ‘chamber effects’ on plant height often described in the literature might be explained by the absence of solar UV‐B radiation in these chambers.
CO2‐concentrating mechanisms: a direct role for thylakoid lumen acidification?
Authors: RAVEN J. A. 
Published: November 2003

ABSTRACTA testable mechanism of CO2 accumulation in photolithotrophs, originally suggested by Pronina & Semenenko, is quantitatively analysed. The mechanism involves (as does the most widely accepted hypothesis) the delivery of HCO3− to the compartment containing Rubisco. It differs in proposing subsequent HCO3− entry (by passive uniport) to the thylakoid lumen, followed by carbonic anhydrase activity in the lumen; uncatalysed conversion of HCO3− to CO2, even at the low pH of the lumen, is at least 300 times too slow to account for the rate of inorganic C acquisition. Carbonic anhydrase converts the HCO3− to CO2 at the lower pH maintained in the illuminated thylakoid lumen by the light‐driven H+ pump, generating CO2 at 10 times or more the thylakoid HCO3− concentration. Efflux of this CO2 can suppress Rubisco oxygenase activity and stimulate carboxylase activity in the stroma. This mechanism differs from the widely accepted hypotheses in the required location of carbonic anhydrase, i.e. in the thylakoid lumen rather than the stroma or pyrenoid, and in the need for HCO3− influx to thylakoids. The capacity for anion (assayed as Cl−) entry by passive uniport reported for thylakoid membranes is adequate for the proposed mechanism; if the Cl− channel does not transport HCO3−, HCO3− entry could be by combination of the Cl− channel with a Cl− HCO3− antiporter. This mechanism is particularly appropriate for organisms which lack overt accumulation of total inorganic C in cells, but which nevertheless have the gas exchange characteristics of an organism with a CO2‐concentrating mechanism.
Combined effects of elevated CO2 and air temperature on carbon assimilation of Pinus taeda trees
Authors: TESKEY R. O. 
Published: November 2003

ABSTRACTBranches of 22‐year‐old loblolly pine (Pinus taeda, L.) trees growing in a plantation were exposed to ambient CO2, ambient + 165 μmol mol−1 CO2 or ambient + 330 μmol mol−1 CO2 concentrations in combination with ambient or ambient + 2°C air temperatures for 3 years. Field measurements in the third year indicated that net carbon assimilation was enhanced in the elevated CO2 treatments in all seasons. On the basis of A/Ci, curves, there was no indication of photosynthetic down‐regulation. Branch growth and leaf area also increased significantly in the elevated CO2 treatments. The imposed 2°C increase in air temperature only had slight effects on net assimilation and growth. Compared with the ambient CO2 treatment, rates of net assimilation were ∼1·6 times greater in the ambient + 165 μmol mol−1 CO2 treatment and 2·2 times greater in the ambient + 330 μmol mol−1 CO2 treatment. These ratios did not change appreciably in measurements made in all four seasons even though mean ambient air temperatures during the measurement periods ranged from 12·6 to 28·2°C. This indicated that the effect of elevated CO2 concentrations on net assimilation under field conditions was primarily additive. The results also indicated that the effect of elevated CO2 (+ 165 or + 330 μmol mol−1) was much greater than the effect of a 2°C increase in air temperature on net assimilation and growth in this species.
Inhibition of photosynthesis by solar radiation in Dunaliella salina: relative efficiencies of UV‐B, UV‐A and PAR
Authors: HERRMANN H. , HÄDER D.‐P. , GHETTI F. 
Published: November 2003

ABSTRACTInhibition of photosynthesis after exposure to solar radiation was investigated in the marine green alga Dunaliella salina by monitoring photosynthetic optimal quantum yield Fv/Fm and efficiency of oxygen production. Samples were exposed to solar radiation in Ancient Korinth, Greece (37°58′ N, 23°0′ E) in August 1994. Within 30 min, Fv/Fm and efficiency of oxygen production decreased with similar kinetics with increasing exposure time. The inhibition, however, diminished when ultraviolet radiation was progressively excluded by means of colour filter glasses. Samples exposed for 3 h showed complete or partial recovery of photosynthesis, with almost the same rate under all irradition conditions. The fit of the experimental data with an analytical model describing inhibition of photosynthesis as a function of a linear combination of the photon fluence in the UV‐B, UV‐A and PAR allows one to estimate the relative mean effectiveness for inhibition by the three spectral ranges [about 2 × 10−4, 4 × 10−6 and 2 × 10−7 (μmol photons m−2)−1 for UV‐B, UV‐A and PAR, respectively].
A sensitive computer‐controlled pH‐stat system allows the study of net H+ fluxes related to nitrogen uptake of intact plants in situ
Authors: WOLLENWEBER B. 
Published: November 2003

ABSTRACTProton fluxes related to the acid–base balance of intact plants were investigated in detail. A multi‐channel titration system was developed in order to regulate the pH in two different sets of nutrient solutions. This system also allowed computation of the dynamics of proton fluxes associated with nutrient uptake in situ.The pH‐stat system presented here has proved to be very reliable and sensitive. By additions of acid or base to the nutrient solutions, the set pH could typically be maintained within 0·01 pH units. Experiments investigating net proton fluxes correlated with nitrogen uptake are described. The results show a rapid response of proton fluxes to changes in the form of nitrogen supplied, indicating that alterations in net proton fluxes are directly induced by the nature of the nitrogen source. The stoichiometry of proton fluxes connected to nitrogen uptake could be followed online, and the results are discussed in relation to the charge and acid–base balances of the whole plant.
UV‐B component of sunlight causes measurable damage in field‐grown maize (Zea mays L.): developmental and cellular heterogeneity of damage and repair
Authors: STAPLETON A. E. , THORNBER C. S. , WALBOT V. 
Published: November 2003

ABSTRACTUltraviolet radiation has diverse morphogenetic and damaging effects on plants. The end point of damage is reduced plant growth, but in the short term UV radiation damages specific cellular components. We measured cyclobutane pyrimidine dimers in maize DNA from plants grown in natural solar radiation. Green maize tissues had detectable DNA damage, roots had less damage, and anthers had much more damage than green leaves. This heterogeneity in damage levels may reflect differences in dose received or in damage repair. The architecture of green tissues had no measurable effects on DNA damage levels, as leaf sheath and leaf blade were equivalent. We observed a slight increase in damage levels in plants sampled at the end of the day, but there was no accumulation of damage over the growing season. We measured photoreactivation, and found substantial levels of this light‐dependent repair in both the epidermis and inner cell layers of leaves, and in all organelles that contain DNA – the nucleus, chloroplasts and mitochondria. We conclude that maize has efficient mechanisms for photorepair of daily UV‐induced DNA damage that prevent accumulation.
The effect of elevated CO2 on the chemical composition and construction costs of leaves of 27 C3 species
Authors: POORTER H. , VAN BERKEL Y. , BAXTER R. , DEN HERTOG J. , DIJKSTRA P. , GIFFORD R. M. , GRIFFIN K. L. , ROUMET C. , ROY J. , WONG S. C. 
Published: November 2003

ABSTRACTWe determined the proximate chemical composition as well as the construction costs of leaves of 27 species, grown at ambient and at a twice‐ambient partial pressure of atmospheric CO2. These species comprised wild and agricultural herbaceous plants as well as tree seedlings. Both average responses across species and the range in response were considered. Expressed on a total dry weight basis, the main change in chemical composition due to CO2 was the accumulation of total non‐structural carbohydrates (TNC). To a lesser extent, decreases were found for organic N compounds and minerals. Hardly any change was observed for total structural carbohydrates (cellulose plus hemicellulose), lignin and lipids. When expressed on a TNC‐free basis, decreases in organic N compounds and minerals were still present. On this basis, there was also an increase in the concentration of soluble phenolics.In terms of glucose required for biosynthesis, the increase in costs for one chemical compound – TNC – was balanced by a decrease in the costs for organic N compounds. Therefore, the construction costs, the total amount of glucose required to produce 1 g of leaf, were rather similar for the two CO2 treatments; on average a small decrease of 3% was found. This decrease was attributable to a decrease of up to 30% in the growth respiration coefficient, the total CO2 respired [mainly for N AD(P)H and ATP] in the process of constructing 1 g of biomass. The main reasons for this reduction were the decrease in organic N compounds and the increase in TNC.
Aluminium speciation in the presence of wheat root cell walls: a wet chemical study
Authors: MASION A. , BERTSCH P. M. 
Published: November 2003

ABSTRACTHydrolysis of Al3+ was performed in the presence of isolated root cell walls from a series of wheat cultivars (Triticum aestivum L.) known to have differential tolerance to Al contamination. Aluminium speciation was dependent on the cell wall concentration. At low cell wall concentrations, significant amounts of the very toxic Al13 species were formed. At higher cell wall concentrations, formation of the tridecamer was hindered or completely inhibited. The sensitive wheat cultivars displayed a higher affinity for aluminium than the tolerant cultivars. A possible Al tolerance mechanism based on cell wall permeability is discussed.
An improved dynamic model of photosynthesis for estimation of carbon gain in sunfleck light regimes
Authors: PEARCY R. W. , GROSS L. J. , HE D. 
Published: November 2003

ABSTRACTA dynamic model of leaf photosynthesis for C3 plants has been developed for examination of the role of the dynamic properties of the photosynthetic apparatus in regulating CO2 assimilation in variable light regimes. The model is modified from the Farquhar‐von Caemmerer‐Berry model by explicitly including metabolite pools and the effects of light activation and deactivation of Calvin cycle enzymes. It is coupled to a dynamic stomatal conductance model, with the assimilation rate at any time being determined by the joint effects of the dynamic biochemical model and the stomatal conductance model on the intercellular CO2 pressure. When parametrized for each species, the model was shown to exhibit responses to step changes in photon flux density that agreed closely with the observed responses for both the understory plant Alocasia macrorrhiza and the crop plant Glycine max. Comparisons of measured and simulated photosynthesis under simulated light regimes having natural patterns of lightfleck frequencies and durations showed that the simulated total for Alocasia was within ±4% of the measured total assimilation, but that both were 12–50% less than the predictions from a steady–state solution of the model. Agreement was within ±10% for Glycine max, and only small differences were apparent between the dynamic and steady–state predictions. The model may therefore be parametrized for quite different species, and is shown to reflect more accurately the dynamics of photosynthesis than earlier dynamic models.
Cytological and structural changes in Pinus pines L. needles following the application of an anionic surfactant
Authors: BUSSOTTI F. , BOTTACCI A. , GROSSONI P. , MORI B. , TANI C. 
Published: November 2003

ABSTRACTIn many coastal areas, synthetic surfactants are present as pollutants in the chemical composition of sea spray. Their phytotoxic action in synergism with sea salt is well known. This paper examines the early effects of an anionic surfactant (sodium alkylbenzene sulphonate = ABS) on the anatomy and ultrastructure of Pinus pinea L. needles. Three successive treatments in the open field on Pinus pinea trees about 2 m in height were carried out in the month of August. The crowns of the trees were sprayed with an aqueous solution containing 1000 g m−3, and subsequently the current‐year needles were observed by light microscopy, as well as by scanning and transimission electron microscopy. A few days after the treatment the needles had turned yellow. The results of the microscopical analysis show that the surfactant is absorbed prevalently through the stomata and that it causes deterioration of the epistomatal wax structures and induces alterations in the stomatal guard cell walls. Lastly, it causes degeneration of the protoplasm in cells of the mesophyll, beginning with the cells closest to the stomatal openings. The efficiency of both photosynthesis and gaseous exchange processes may be affected.
Elevated atmospheric CO2 differentially affects needle chloroplast ultrastructure and phloem anatomy in Pinus palustris: interactions with soil resource availability
Authors: PRITCHARD S. G. , PETERSON C. M. , PRIOR S. A. , ROGERS H. H. 
Published: November 2003

ABSTRACTThe response of forest species to increasing atmospheric CO2, particularly under resource limitations, will require study in order to predict probable changes which may occur at the plant, community and ecosystem levels. Longleaf pine (Pinus palustris Mill.) seedlings were grown for 20 months at two levels of CO2 (365 and 720 μol mol1) in two levels of soil nitrogen (4 and 40 g m−2), and with two levels of soil moisture (–0·5 and –1·5 MPa xylem pressure potential). Leaf tissue was collected in the spring (12 months exposure) and autumn (20 months exposure) and examined using transmission electron microscopy (TEM) and light microscopy. During early spring, elevated CO2 magnified effects of N and water treatment on starch accumulation and in some cases contributed to altered organization of mesophyll chloroplasts. Disruption of chloroplast integrity was pronounced under elevated CO2, low N and water stress. In autumn, needles contained little starch; however, chloroplasts grown under high CO2 exhibited stress symptoms including increased plastoglobuli and shorter grana. A trend for reduced needle phloem cross‐sectional area resulting from fewer sieve cells was also observed under elevated CO2. These results suggest that, in nature, longleaf pine seedlings may not benefit from a doubling of CO2, especially when soil resources are limiting.
Pityriasis lichenoides et varioliformis acuta in HIV‐1 + patients: a marker of early stage disease
Authors: Smith Kathleen J. , Nelson Ann , Skelton Henry , Yeager Josef , Wagner Kenneth R ,   The Military Medical Consortium for the Advancement of Retroviral Research (MMCARR)
Published: November 2003

Abstract Background The high incidernce of cutaneous disease in HIV‐1 + patients may be a marker of the chronic state of immune activation. In addition, specific cutaneous diseases may be related to the pattern and degree of immune dysregulation present in the patients at the time of the eruption. We have observed that HIV‐1 + patients with pityriasis lichenoides et varioliformis acuta (PLEVA) were in the early to midstage of HIV‐1 disease. Materials and methods To determine if there was a correlation between the phenotype of the lymphoid infiltrate and surface markers of the epidermis and the known changes in early or late‐stage HIV‐1 disease, we studied five HIV‐1 + patients with PLEVA. Cutaneous biopsy specimens were obtained and immunohistochemical stains were used to determine the expression of ELAM‐1, ICAM‐1, and HLA‐DR and the phenotype of the lymphoid infiltrate. Results The HIV‐1 + patients showed increased expression of HLA‐DR on keratinocytes as well as on the mononuclear and dendritic cell populations in the epidermis and dermis. The majority of T cells were activated CD8+ cells. Conclusions Immunophenotyping of the inflammatory infiltrate in these patients is consistent with a pattern of immune dysregulation seen only in earlier stages of HIV‐1 disease. Thus, PLEVA may be useful as a marker of early to midstages of HIV‐1 disease.
Group therapy: a useful and supportive treatment for psoriasis patients
Authors: Seng Tan Kang , Nee Tham Siew 
Published: November 2003

Abstract Background Because of the social and psychologic effects of psoriasis, many patients with the disease experience considerable emotional stress which in turn can aggravate the disease. This study was undertaken to determine the usefulness of group therapy in helping psoriasis patients cope with their condition. Methods A structured program consisting of seven sessions was carried out with 10 psoriasis patients under the guidance of a social worker. The program covered knowledge of psoriasis, feelings of acceptance, stress management, and coping with daily living. An evaluation was carried out at the end of the program. Results Most patients found that the program enhanced their knowledge of psoriasis and helped them to cope better, and that they also learned from each other how to handle stress and gained self‐confidence. Conclusion Group therapy is a useful adjuvant therapy for psoriasis patients in coping with their illness.
A 2‐year study of liquid nitrogen therapy in cutaneous leishmaniasis
Authors: Al‐Majali Osama , Routh Hirak Behari , Abuloham Obad , Bhowmik Kazal Rekha , Muhsen Muhammed , Hebeheba Haider 
Published: November 2003

Abstract Background Among the different modalities for treatment of cutaneous leislnmaniasis, liquid nitrogen is considered an effective therapy with very mild side‐effects. Methods A study was conducted using liquid nitrogen topically for the treatment of cutaneous leishmaniasis in the King Hussain Medical Centre, Amman‐Jordan. Among 468 patients of cutaneous leishmaniasis, 293 were treated with liquid nitrogen and the rest were treated with other known treatment modalities. Results Of the patients treated with cryo surgery liquid nitrogen, 215 of 293 permitted appropriate follow‐up; the clinical response was significant and effective. No systemic adverse effects were noted. Mild cutaneous complications were infrequent, and included hypopigmentation, hyperpigmentation, and scar formation. Conclusions From the results of this study, liquid nitrogen therapy may be considered an effective treatment for cutaneous leishmaniasis.