bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ion transport and metal sensitivity of vacuolar channels from the roots of the aquatic plant Eichhornia crassipes
Authors: Paganetto A. , Carpaneto A. , Gambale F. 
Published: March 2003

AbstractUsing the patch‐clamp technique, we investigated the transport properties of vacuolar ion channels from the roots of water hyacinth, Eichhornia crassipes (Mart. Solms, Pontederiacae). Eichhornia crassipes vacuoles displayed large voltage‐dependent rectifying slow‐vacuolar (SV) currents, which activated in a few seconds at positive potentials and deactivated at negative voltages in a few hundreds of millseconds. Similarly to SV channel previously identified in the tonoplast of terrestrial plants, SV currents in E. crassipes were activated by micromolar concentrations of Ca2+ and current slightly increased (25%) on addition (10 mm) of the reducing agent dithiothreitol (DTT). Eichhornia crassipes SV channels were equally permeable to K+ and Na+. The permeability sequence derived from current values is: K+ ≈ Na+ > Rb+ > NH4+ ≈ Cs+ >> TEA+. Excised membrane patches displayed single channel transitions typical of SV‐type single channel openings with a conductance of (83·0 ± 5·6) pS; a smaller channel with a conductance of (31·0 ± 2·7) pS was also identified. Metals such as Ni2+ and Zn2+ decreased the vacuolar current in a reversible manner. However, although Zn2+ inhibition is comparable to that induced by the same metal in vacuoles from the main root of sugar beet (Beta vulgaris L.), the inhibition of the SV currents by Ni2+ is not as substantial in E. crassipes as in sugar beet. To our knowledge, this is the first electrophysiological characterization of ionic transport in E. crassipes, a pervasive troublesome aquatic weed, which has exceptional absorption properties of several water contaminants such as heavy metals, pesticides and phenols.
The effect of drought and ultraviolet radiation on growth and stress markers in pea and wheat
Authors: Alexieva V. , Sergiev I. , Mapelli S. , Karanov E. 
Published: March 2003

AbstractIt emerged recently that there is an inter‐relationship between drought and ultraviolet‐B (UV‐B) radiation in plant responses, in that both stresses provoke an oxidative burst. The purpose of this investigation was to compare the effects and interaction of drought and UV‐B in wheat and pea. The absence of changes in relative leaf water content (RWC) after UV‐B treatments indicate that changes in water content were not involved. RWC was the main factor resulting in reduced growth in response to drought. Increases in anthocyanin and phenols were detected after exposure to UV‐B. The increases do not appear to be of sufficient magnitude to act as a UV‐B screen. UV‐B application caused greater membrane damage than drought stress, as assessed by lipid peroxidation as well as osmolyte leakage. An increase in the specific activities of antioxidant enzymes was measured after UV‐B alone as well as after application to droughted plants. Proline increased primarily in drought‐stressed pea or wheat. Proline may be the drought‐induced factor which has a protective role in response to UV‐B. The physiological and biochemical parameters measured indicate the UV‐B light has stronger stress effectors than drought on the growth of seedlings of both species. The two environmental stresses acted synergistically to induce protective mechanisms in that pre‐application of either stress reduced the damage caused by subsequent application of the other stress.
N2 fixation by Acacia species increases under elevated atmospheric CO2
Authors: Schortemeyer M. , Atkin O. K. , McFarlane N. , Evans J. R. 
Published: March 2003

AbstractIn the present study the effect of elevated CO2 on growth and nitrogen fixation of seven Australian Acacia species was investigated. Two species from semi‐arid environments in central Australia (Acacia aneura and A. tetragonophylla) and five species from temperate south‐eastern Australia (Acacia irrorata, A. mearnsii, A. dealbata, A. implexa and A. melanoxylon) were grown for up to 148 d in controlled greenhouse conditions at either ambient (350 µmol mol−1) or elevated (700 µmol mol−1) CO2 concentrations. After establishment of nodules, the plants were completely dependent on symbiotic nitrogen fixation. Six out of seven species had greater relative growth rates and lower whole plant nitrogen concentrations under elevated versus normal CO2. Enhanced growth resulted in an increase in the amount of nitrogen fixed symbiotically for five of the species. In general, this was the consequence of lower whole‐plant nitrogen concentrations, which equate to a larger plant and greater nodule mass for a given amount of nitrogen. Since the average amount of nitrogen fixed per unit nodule mass was unaltered by atmospheric CO2, more nitrogen could be fixed for a given amount of plant nitrogen. For three of the species, elevated CO2 increased the rate of nitrogen fixation per unit nodule mass and time, but this was completely offset by a reduction in nodule mass per unit plant mass.
Cadmium causes the oxidative modification of proteins in pea plants
Authors: Romero‐Puertas M. C. , Palma J. M. , Gómez M. , Del Río L. A. , Sandalio L. M. 
Published: March 2003

AbstractIn pea (Pisum sativum L.) leaves from plants grown in the presence of 50 µm CdCl2 the oxidative production of carbonyl groups in proteins, the rate of protein degradation and the proteolytic activity were investigated. In leaf extracts the content of carbonyl groups measured by derivatization with 2,4‐dinitrophenylhydrazine (DNPH), was two‐fold higher in plants treated with Cd than in control plants. The identification of oxidized proteins was carried out by sodium dodecyl sulphate‐polyacrylamide gel electrophoresis of proteins derivatized with DNPH and immunochemical detection with an antibody against DNPH. The intensity of the reactive bands was higher in plants exposed to Cd than in controls. By using different antibodies some of the oxidized proteins were identified as Rubisco, glutathione reductase, manganese superoxide dismutase, and catalase. The incubation of leaf crude extracts with increasing H2O2 concentrations showed a progressive enhancement in carbonyl content and the pattern of oxidized proteins was similar to that found in Cd‐treated plants. Oxidized proteins were more efficiently degraded, and the proteolytic activity increased 20% due to the metal treatment. In peroxisomes purified from pea leaves a rise in the carbonyl content similar to that obtained in crude extracts from Cd‐treated plants was observed, but the functionality of the peroxisomal membrane was not apparently affected by Cd. Results obtained demonstrate the participation of both oxidative stress, probably mediated by H2O2, and proteolytic degradation in the mechanism of Cd toxicity in leaves of pea plants, and they appear to be involved in the Cd‐induced senescence previously reported in these plants.
Drought can be more critical in the shade than in the sun: a field study of carbon gain and photo‐inhibition in a Californian shrub during a dry El Niño year
Authors: Valladares F. , Pearcy R. W. 
Published: March 2003

AbstractDiurnal courses of leaf water potential (Ψl), gas exchange and chlorophyll fluorescence were measured in natural sun and shade populations ofHeteromeles arbutifoliathroughout the seasons of an unusually dry El Niño year in Central California. The onset of drought resulted in decreased stomatal conductance and net photosynthesis in both sun and shade plants. However, the decline inΨlwas much greater and carbon gain was much more strongly limited by the development of drought stress in the shade than in the sun. Photorespiratory energy dissipation was significantly higher in the sun than in the shade in spring and autumn, but not during the summer. Pre‐dawn photochemical efficiency (Fv/Fm) was significantly higher in the shade than in the sun during the spring but the differences disappeared during the summer and autumn. The strong irradiance in the open field site studied led to a chronic but only mild reduction inFv/Fm, with values around 0·79. Summer sunflecks led to a sustained photo‐inhibition in shade plants, which exhibited a significant reduction in pre‐dawnFv/Fmof 10% with the onset of drought. Photo‐inhibition became relatively more important for carbon gain in the shade than in the sun due to the low photochemical efficiency under the low light that follows sunflecks. Sun plants ofH. arbutifoliaexhibited a rather efficient photoprotection against strong irradiance conferred by both the architecture of the crown and the physiology of the leaves. There is evidence that El Niño events and the associated droughts have become more frequent and severe. Counter‐intuitively, the effects on plant performance of such extreme droughts could be more critical in the shade than in the sun.
Improvement in ozone tolerance of tobacco plants with an antisense DNA for 1‐aminocyclopropane‐1‐carboxylate synthase
Authors: Nakajima N. , Itoh T. , Takikawa S. , Asai N. , Tamaoki M. , Aono M. , Kubo A. , Azumi Y. , Kamada H. , Saji H. 
Published: March 2003

AbstractAntisense DNA for an ozone‐inducible 1‐aminocyclopropane‐1‐carboxylate (ACC) synthase (EC 4.4.1.14; LE‐ACS6) from tomato, under the control of the cauliflower mosaic virus 35S promoter, was introduced into tobacco to generate transgenic plants. Lower rates of ozone‐induced ethylene production were observed in three of seven transgenic plants than in the wild‐type plants. Ozone‐induced visible damage was attenuated in these three lines, and the extent of damage was positively related to the level of ozone‐induced ethylene production. In the most ozone‐resistant line, ozone‐induced accumulation of ACC and levels of transcripts for ozone‐inducible endogenous ACC synthases were suppressed compared with those in wild‐type plants, demonstrating that ozone‐inducible ACC synthases have a key role in the expression of leaf damage by ozone exposure. No significant differences in growth and morphology were observed between transgenic and wild‐type plants. Stomatal conductance of transgenic plants during ozone exposure was higher than that of wild‐type plants. These findings indicate that the introduction of antisense DNA for an ozone‐inducible ACC synthase can improve the ozone tolerance of plants without reducing their gas absorption and productivity.
A technique for measuring xylem hydraulic conductance under high negative pressures
Authors: Cochard H. 
Published: March 2003

AbstractA technique for measuring hydraulic conductances of excised xylem segments exposed to high negative pressures is described. A centrifugal force is used to generate negative pressures (P) in the sample and to create a positive hydrostatic pressure difference (ΔP) between its two ends. ΔP forces water through the sample at a flow rate (F) determined optically during centrifugation. The sample hydraulic conductance k is derived from F and ΔP. The sample vulnerability curve is given by the dependence of k on P. Results for Cedrus atlantica Manetti and Laurus nobilis L. shoots are given. The technique is appropriate for the analysis of xylem refilling under negative pressure.
A computer‐operated routine of gas exchange and optical measurements to diagnose photosynthetic apparatus in leaves
Authors: Laisk A. , Oja V. , Rasulov B. , Rämma H. , Eichelmann H. , Kasparova I. , Pettai H. , Padu E. , Vapaavuori E. 
Published: March 2003

AbstractPhotosynthesis is a complex process whose rate is affected by many biochemical and biophysical factors. Fortunately, it is possible to determine, or at least estimate, many of the most important parameters using a combination of optical methods and gas transient analyses. We describe here a computer‐operated routine that has been developed to make detailed assessments of photosynthesis at a comprehensive level. The routine comprised the following measurements: steady‐state light and CO2response curves of net CO2assimilation at 21 and 2 kPa O2; transients from limiting to different saturating CO2concentrations at 2 kPa O2; post‐illumination CO2fixation transient; dark–light induction of O2evolution; O2yield from one saturating single‐turnover flash; chlorophyll fluorescenceF0,FsandFmduring the light and CO2response curves; leaf transmission at 820 nm (P700+) during the light and CO2response curves; post‐illumination re‐reduction time of P700+. The routine was executed on a two‐channel fast‐response gas exchange measurement system (A. Laisk and V. Oja:Dynamic Gas Exchange of Leaf Photosynthesis.CSIRO, Canberra, Australia). Thirty‐six intrinsic characteristics of the photosynthetic machinery were derived, including quantum yield of CO2fixation (YCO2), time constant of P700 re‐reduction (τ′), relative optical cross‐sections of PSII and PSI antennae (aII,aI), PSII and PSI density per leaf area unit, plastoquinone pool, total mesophyll resistance, mesophyll diffusion resistance,Vm,Km(CO2) and CO2/O2specificity of Rubisco, RuBP pool at CO2limitation (assimilatory charge). An example of the routine and calculations are shown for one leaf and data are presented for leaves of 8‐year‐old‐trees of two birch clones growing in Suonenjoki Forest Research Station, Finland, during summer 2000. ParametersYCO2, basicτ′,aII,aI,Km(CO2) andKsvaried little in different leaves [relative standard deviation (RSD) < 7%], other parameters scattered widely (RSD typically 10–40%). It is concluded that the little scattered parameters are determined by basic physico‐chemical properties of the photosynthetic machinery whereas the widely scattered parameters are adjusting to growth conditions. The proposed non‐destructive routine is suitable for diagnosing the photosynthetic machinery of leaves and may be applied in plant ecophysiology and in genetic engineering of plants.
Sapwood hydraulic conductivity and leaf area – sapwood area relationships following thinning of aEucalyptus nitensplantation
Authors: Medhurst J. L. , Beadle C. L. 
Published: March 2003

AbstractThis study tested the hypothesis that the relationship between leaf area (projected, or one‐sided) and sapwood area inEucalyptus nitens(Deane and Maiden) Maiden is affected by thinning treatment. However, no difference in the relationship between leaf area and sapwood area was found 8 years after thinning. This result suggests that a single regression equation can be used to predict the leaf area of trees in thinned and unthinned stands. The relationship was non‐linear, implying a causal relationship between growth rate and the ratio of leaf area to sapwood area (Al : As). Sapwood hydraulic conductivity increased by approximately 100% from breast height to crown base, whereas sapwood area decreased by 19%. This implies that the efficiency of water transport through the sapwood increased by 60% along this length. This conclusion is supported by theAl : Asrelationships which showed that the sapwood area at crown base supported, on average, close to 60% more leaf area than a similar amount of sapwood area at breast height. That large trees in this study had greater hydraulic conductivity and higherAl : Aslends support to the argument that resource capture, and hence growth rate, influence sapwood hydraulic conductivity.
Temperature response of parameters of a biochemically based model of photosynthesis. II. A review of experimental data
Authors: Medlyn B. E. , Dreyer E. , Ellsworth D. , Forstreuter M. , Harley P. C. , Kirschbaum M. U. F. , Le Roux X. , Montpied P. , Strassemeyer J. , Walcroft A. , Wang K. , Loustau D. 
Published: March 2003

AbstractThe temperature dependence of C3 photosynthesis is known to vary with growth environment and with species. In an attempt to quantify this variability, a commonly used biochemically based photosynthesis model was parameterized from 19 gas exchange studies on tree and crop species. The parameter values obtained described the shape and amplitude of the temperature responses of the maximum rate of Rubisco activity (Vcmax) and the potential rate of electron transport (Jmax). Original data sets were used for this review, as it is shown that derived values of Vcmax and its temperature response depend strongly on assumptions made in derivation. Values of Jmax and Vcmax at 25 °C varied considerably among species but were strongly correlated, with an average Jmax : Vcmax ratio of 1·67. Two species grown in cold climates, however, had lower ratios. In all studies, the Jmax : Vcmax ratio declined strongly with measurement temperature. The relative temperature responses of Jmax and Vcmax were relatively constant among tree species. Activation energies averaged 50 kJ mol−1 for Jmax and 65 kJ mol−1 for Vcmax, and for most species temperature optima averaged 33 °C for Jmax and 40 °C for Vcmax. However, the cold climate tree species had low temperature optima for both Jmax(19 °C) and Vcmax (29 °C), suggesting acclimation of both processes to growth temperature. Crop species had somewhat different temperature responses, with higher activation energies for both Jmax and Vcmax, implying narrower peaks in the temperature response for these species. The results thus suggest that both growth environment and plant type can influence the photosynthetic response to temperature. Based on these results, several suggestions are made to improve modelling of temperature responses.
Spatial separation of light perception and growth response in maize root phototropism
Authors: Mullen J. L. , Wolverton C. , Ishikawa H. , Hangarter R. P. , Evans M. L. 
Published: March 2003

AbstractAlthough the effects of gravity on root growth are well known and interactions between light and gravity have been reported, details of root phototropic responses are less documented. We used high‐resolution image analysis to study phototropism in primary roots of Zea mays L. Similar to the location of perception in gravitropism, the perception of light was localized in the root cap. Phototropic curvature away from the light, on the other hand, developed in the central elongation zone, more basal than the site of initiation of gravitropic curvature. The phototropic curvature saturated at approximately 10 µmol m−2 s−1 blue light with a peak curvature of 29 ± 4°, in part due to induction of positive gravitropism following displacement of the root tip from vertical during negative phototropism. However, at higher fluence rates, development of phototropic curvature is arrested even if gravitropism is avoided by maintaining the root cap vertically using a rotating feedback system. Thus continuous illumination can cause adaptation in the signalling pathway of the phototropic response in roots.
The Ball–Berry–Leuning and Tardieu–Davies stomatal models: synthesis and extension within a spatially aggregated picture of guard cell function
Authors: Dewar R. C. 
Published: March 2003

AbstractA new model of stomatal conductance is proposed which combines the essential features of the Ball–Berry–Leuning (BBL) and Tardieu–Davies (TD) models within a simple spatially aggregated picture of guard cell function. The model thus provides a coherent description of stomatal responses to both air and soil environments. The model also presents some novel features not included in either the BBL or TD models: stomatal sensing of intercellular (rather than leaf surface) CO2concentration; an explanation of all three observed regimes (A, B and C) of the stomatal response to air humidity (MonteithPlant, Cell and Environment18, 357–364, 1995); incorporation of xylem embolism; and maintenance of hydraulic homeostasis by combined hydraulic and chemical signalling in leaves (in which leaf epidermal hydraulic conductivity plays a key role). Significantly, maintenance of hydraulic homeostasis in the model does not require a direct feedback signal from xylem embolism, the predicted minimum leaf water potential being independent of xylem hydraulic conductivity. It is suggested that stomatal regulation through combined hydraulic and chemical signalling in leaves and/or roots provides a general mechanism enabling plants to maintain their water potentials above a minimum value. Natural selection of the key stomatal parameters would then set the minimum potential to a specific value determined by the most vulnerable plant process under water stress (e.g. cell growth, protein synthesis or xylem cavitation), depending on species and growth conditions.
Shoot P status regulates cluster‐root growth and citrate exudation in Lupinus albus grown with a divided root system
Authors: SHANE M. W. , DE VOS M. , DE ROOCK S. , LAMBERS H. 
Published: March 2003

ABSTRACTThe present study was carried out to investigate whether the P concentration in the roots or the shoots controls the growth and citrate exudation of cluster roots in white lupin (Lupinus albus L). Foliar P application indicated that low P concentration in the shoots enhanced cluster‐root growth and citrate‐exudation rate more so than low P concentration in the roots. In the split‐root study, the P concentration in the shoots increased with increased P supply (1, 25 or 75 mmol m−3 P), to the ‘privileged’ root halves. Roots ‘deprived’ of P invariably had the same low P concentrations, whereas those in the ‘privileged’ roots increased with increasing P supply (1, 25 or 75 mmol m−3 P). Nevertheless, the proportion of the total root mass allocated to cluster roots, and the citrate‐exudation rates from the root halves were always similar on both root halves, irrespective of P supply, and decreased with increasing shoot P concentrations. Peak citrate exudation rates from developing cluster roots were significantly faster from cluster roots on the ‘deprived’ root halves when the ‘privileged’ half was exposed to 1 mmol m−3 P as compared with 25 or 75 mmol m−3 P. The possibility that changes in the concentrations of P fractions in the root halves influenced cluster‐root growth and citrate exudation was discounted, because there were no significant differences in insoluble organic P, ester‐P and inorganic P among all ‘deprived’ root halves. The results indicate that cluster‐root proportions and citrate exudation rates were regulated systemically by the P status of the shoot, and that P concentrations in the roots had little influence on growth and citrate exudation of cluster roots in L. albus.
Parameterization of the CO2 and H2O gas exchange of several temperate deciduous broad‐leaved trees at the leaf scale considering seasonal changes
Authors: KOSUGI Y. , SHIBATA S. , KOBASHI S. 
Published: March 2003

ABSTRACTA combined model to simulate CO2 and H2O gas exchange at the leaf scale was parameterized using data obtained from in situ leaf‐scale observations of diurnal and seasonal changes in the CO2 and H2O gas exchange of four temperate deciduous broad‐leaved trees using a porometric method. The model consists of a Ball et al. type stomatal conductance submodel [Ball, Woodrow & Berry, pp. 221–224 in Progress in Photosynthesis Research (ed. I. Biggins), Martinus‐Nijhoff Publishers, Dordrecht, The Netherlands, 1987] and a Farquhar et al. type biochemical submodel of photosynthesis (Farquhar, von Caemmerer & Berry, Planta 149, 78–90, 1980). In these submodels, several parameters were optimized for each tree species as representative of the quantitative characteristics related to gas exchange. The results show that the seasonal physiological changes of Vcmax25 in the biochemical model of photosynthesis should be used to estimate the long‐term CO2 gas exchange. For Rd25 in the biochemical model of photosynthesis and m in the Ball et al. type stomatal conductance model, the difference should be counted during the leaf expansion period.