bluuebunny/crossref_metadata_2025_split huggingface dataset:
Plant distribution and the temperature coefficient of metabolism
Authors: CRIDDLE R. S. , HOPKIN M. S. , McARTHUR E. D. , HANSEN L. D. 
Published: April 2006

ABSTRACTThe spatial distribution of a plant species is limited by the range of climatic conditions to which the species can adapt. Temperature is one of the most significant determinants of plant distribution, but except for the effects of lethal limits, little is known about physiological changes in responses to differences in environmental temperature. In this study, temperature coefficients of non‐photosynthetic metabolism have been determined in the normal environmental temperature range for selected annual and perennial plants. Distinct differences were found in the temperature coefficient of metabolism of woody perennial plants from high latitudes and high elevations and closely related low‐latitude and low‐elevation plants. Low‐latitude and low‐elevation woody perennials have Arrhenius temperature coefficients for metabolism that are larger than those for congeneric high‐latitude and high‐elevation plants. The Arrhenius temperature coefficient is not rapidly adapted to new environments. A simple function was developed relating Arrhenius temperature coefficient to latitude and elevation for accessions of three, woody, perennial species complexes of plants collected from a wide geographic range but grown in common gardens. Within these taxa, plants that experience broader ranges of temperature during growth in their native habitat have smaller temperature coefficients. Temperature coefficients also varied with growth stage or season. No similar relationship was found for annuals and herbaceous perennials. For the plants tested, Arrhenius temperature coefficients are high during early spring growth, but shift to lower values later in the season. The shift in Arrhenius temperature coefficients occurs early in the season for southern and low‐elevation plants and progressively later for plants from further north or higher elevation. The changes in Arrhenius temperature coefficients result largely from increases in plant metabolic rates at lower temperatures while little change occurs in the rates at higher temperatures. Altering the temperature dependence of the control of metabolic rate is apparently an important means of response to climate change.
Differential stimulation of an arid‐environment winter ephemeral Dimorphotheca pluvialis (L.) Moench by ultraviolet‐B radiation under nutrient limitation
Authors: MUSIL C. F. , WAND S. J. E. 
Published: April 2006

ABSTRACTA South African winter ephemeral D. pluvialis was exposed, under low and high nutrient conditions, to four different daily doses of biologically effective UV‐B radiation. These simulated different depletions (range 0–30%) in the ozone layer at the southerly distribution limit (33° 56′S) of this species, and included daily UV‐B doses received at the northerly distribution limit (26° 38′S) without ozone depletion. Growth inhibition by increased UV‐B radiation was observed during early vegetative stages, but only under low nutrient conditions. Thereafter, net CO2 assimilation rate, growth and reproduction were stimulated by an increase in UV‐B radiation, though doses above those approximating a 20% ozone depletion appeared to be inhibitory. Differential stimulation occurred in the two nutrient treatments. Under high nutrient conditions, photosynthesis (specifically carboxylation efficiency), and numbers of leaves, inflorescences and diaspores per plant, and leaf areas increased, but leaf thickness decreased with increased UV‐B radiation. Under low nutrient conditions, dry masses of leaves, stems, inflorescences and diaspores, and total above‐ground dry masses increased with increased UV‐B radiation. Foliar organic carbon and nitrogen concentrations and foliar concentrations of UV‐B absorbing compounds were unaffected by increased UV‐B radiation, but foliar P concentrations declined. Diaspore viability declined with increased UV‐B radiation. The net effect was a 35 to 43% reduction in viable diaspore production under high nutrient conditions at UV‐B doses equivalent to those currently received at the northerly distribution limit during the reproductive phase. It is concluded that anticipated increases in UV‐B radiation could reduce regeneration success, and seedling survival in areas of low soil fertility, particularly at lower latitudes, and consequently increase the risk of localized population extinctions from stochastic causes.
Control of steady‐state photosynthesis in sunflowers growing in enhanced CO2
Authors: WOODROW I. E. 
Published: April 2006

ABSTRACTControl coefficients were used to describe the degree to which ribulose bisphosphate carboxylase/oxygenase (Rubisco) limits the steady‐state rate of CO2 assimilation in sunflower leaves from plants grown at high (800 μmol mol−1) and low (350 μmol mol−1) CO2. The magnitude of a control coefficient is approximately the percentage change in the flux that would result from a 1% rise in enzyme active site concentration. In plants grown at low CO2, leaves of different ages varied considerably in their photosynthetic capacities. In a saturating light flux and an ambient CO2 concentration of 350 μmol mol−1, the Rubisco control coefficient was about 0.7 in all leaves, indicating that Rubisco activity largely limited the assimilation flux. The Rubisco control coefficient for leaves grown at 350 μmol mol−1 CO2 dropped to about zero when the ambient CO2 concentration was raised to 800 μmol mol−1. In relatively young, fully expanded leaves of plants grown at high CO2, the Rubisco control coefficient was also about 0.7 at a saturating light flux and at the CO2 concentration at which the plants were grown (800 μmol mol−1). This apparently resulted from a decrease in the concentration of Rubisco active sites. In older leaves, however, the control coefficient was about 0.2. Because, on the whole, Rubisco activity still largely limits the assimilation flux in plants grown at high CO2, the kinetics of this enzyme can still be used to model photosynthesis under these conditions. The relatively high Rubisco control coefficient under enhanced CO2 indicates that the young sunflower leaves have the capacity to acclimate their photosynthetic biochemistry in a way consistent with an optimal use of protein resources.
Induction of PPi‐dependent phosphofructokinase by phosphate starvation in seedlings of Brassica nigra
Authors: THEODOROU M. E. , PLAXTON W. C. 
Published: April 2006

ABSTRACTActivity of PPi‐dependent phosphofructokinase (PFP) was monitored in Brassica nigra seedlings grown under nutrient‐sufficient or phosphate (Pi)‐starved conditions. Roots, stems and leaves of 50 d Pi‐deficient seedlings displayed 4.0‐, 3.7‐ and 2.3‐fold greater PFP activity, respectively, than did nutrient sufficient controls. This induction was based primarily upon an increased susceptibility of PFP from the Pi‐starved tissues to activation by fructose‐2,6‐bisphosphate. The ratio of PFP to ATP‐dependent phosphofructokinase (PFK) was approximately 2:1 and 1:1 in the various organs of 50 d Pi‐starved and Pi‐fed plants, respectively. Immunoblots probed with anti‐(potato PFP) immune serum revealed that the induction of PFP in Pi‐starved B. nigra was coincident with an elevation in the amount of PFP α‐subunit in the leaves as well as an increase in the α:β subunit ratio in the stems and roots. Induction of PFP in the various tissues was also accompanied by an appreciable decline in intracellular Pi level, decreased soluble protein content, and elevated phosphoenolpyruvate phosphatase activity. Time course studies revealed that these responses to Pi stress were significantly delayed in the leaves as compared to the roots and stems suggesting that Pi may be preferentially sequestered to the leaves during Pi starvation. These data also provide further evidence that B. nigra PFP is an adaptive enzyme that may function during Pi deprivation as: (1) a glycolytic bypass to PFK; and (2) a ‘Pi‐recycling system’ that converts esterified‐P to Pi that would be rapidly reassimilated into the metabolism of the Pi‐deficient cells.
The importance of the ratio UV‐B/photosynthetic active radiation (PAR) during leaf development as determining factor of plant sensitivity to increased UV‐B irradiance: effects on growth, gas exchange and pigmentation of bean plants (Phaseolus vulgaris cv. Label)
Authors: DECKMYN G. , MARTENS C. , IMPENS I. 
Published: April 2006

ABSTRACTTo evaluate the effect of different naturally occurring irradiation conditions on the sensitivity of bean (Phaseolus vulgaris cv. Label) to increased UV‐B levels, plants were grown under six different light treatments. In the control series (at ambient levels of UV‐B), UV‐B and visible light were decreased in parallel, resulting in three different total irradiation treatments with the same UV‐B/PAR ratio. A second series with a 15% increase in UV‐B irradiation at each PAR level was used to investigate the effect of UV‐B under the varying total irradiance levels. The different total irradiance levels resulted in large differences in total dry weight, specific leaf weight, photosynthesis‐light response and pigment concentrations. Nevertheless, the 15% increase in UV‐B resulted in equal reductions in total dry weight (from 24.5 to 34.3%) and effective photosynthesis for all light levels. The accumulation of protective pigments in the primary bean leaves was strongly correlated to the total irradiance level (200% increase from the lowest to the highest light level), but was not influenced by increasing UV‐B levels. As the UV‐B/PAR ratio outside increases with decreasing total irradiance (when induced by cloud cover) this implies that low radiation levels are potentially dangerous to some plants, even though the UV‐B levels may seem negligible.
Growth cycle stage‐dependent NaCl induction of plasma membrane H+‐ATPase mRNA accumulation in de‐adapted tobacco cells
Authors: PEREZ‐PRAT E. , NARASIMHAN M. L. , NIU X. , BOTELLA M. A. , BRESSAN R. A. , VALPUESTA V. , HASEGAWA P. M. , BINZEL M. L. 
Published: April 2006

ABSTRACTA cDNA clone encoding an isoform of the plasma membrane H+‐ATPase was isolated from Nicotiana tabacum. The steady‐state plasma membrane H+‐ATPase message levels were the same in unadapted tobacco cells and tobacco cells adapted to 428 mol m−3 NaCl. When cells adapted to 428 mol m−3 NaCl maintained in the absence of NaCl (deadapted) for an excess of 100 passages were exposed to 400 mol m−3 NaCl for 24 h, there was an increased accumulation of plasma membrane H+‐ATPase message. The NaCl responsiveness of the deadapted cells was dependent upon the growth cycle stage. Alterations in the levels of plasma membrane FT‐ATPase message during the growth cycle support a role for the H+‐ATPase in cell growth. These results document the induction by NaCl of plasma membrane FT‐ATPase message accumulation in tobacco cells, and suggest that enhanced expression of the plasma membrane FT‐ATPase has a role in the short term response of cells of NaCl, but is not necessarily involved in long‐term adaptation.
Starch metabolism in germinating soybean cotyledons is sensitive to clinorotation and centrifugation
Authors: BROWN C. S. , PIASTUCH W. C. 
Published: April 2006

ABSTRACTSoybean (Glycine max [L.] Merr. cv. McCall) seedlings germinated and grew for 6d under the altered gravity conditions of horizontal clinorotation and centrifugation. Both of these conditions resulted in decreased growth relative to the control (vertically rotated) plants. Starch concentration in the cotyledons was lower in the clinorotated plants and was higher in the centrifuged plants compared to the controls. The opposite relationship was noted for total lipid concentration. Of the six starch metabolic enzyme activities measured, only ADP glucose pyrophosphorylase was affected by the gravity treatments; being lower in the cotyledons of the horizontally rotated plants and higher in the cotyledons of the centrifuged plants relative to the control values.
Speculations on carbon dioxide starvation, Late Tertiary evolution of stomatal regulation and floristic modernization
Authors: ROBINSON J. M. 
Published: April 2006

ABSTRACTAmbient atmospheric CO2concentration ([CO2]a) has apparently declined from values above 200μmol mol−1to values below 200μmol mol−1within the last several million years. The lower end of this range is marginal for C3plants. I hypothesize that: (1) declining [CO2]aimposed a physiological strain on plants, and plant taxa evolving under declining [CO2]atended to develop compensating mechanisms, including increased stomatal efficiency; (2) angiosperms were better able to adjust to declining [CO2]athan were gymnosperms and pteridophytes; and (3) angiosperm adjustment has been uneven. Fast‐evolving taxa (e.g. grasses and herbs) have been better able to adapt to CO2starvation. If these propositions are true, stomatal adjustment mechanisms should show patterned variation, and a single pattern of stomatal regulation cannot be assumed.
A modelling analysis of the effects of climatic warming on the probability of spring frost damage to tree species in The Netherlands and Germany
Authors: KRAMER K. 
Published: April 2006

ABSTRACTTwo studies presented in the literature (Murray, Canned & Smith 1989; Hanninen 1991) evaluate the effect of increasing winter temperature on the probability of spring frost damage to trees, but yield contradictory results. It is unclear whether the disparity can be ascribed to the fact that different models were used, or is the result of different climatic warming scenarios being used, or is because the tree species at the different locations do indeed respond differently to warmer winters. To evaluate the effects of climatic warming to tree species in The Netherlands and in Germany, both models were fitted to long series of observations on the date of leaf unfolding of eleven tree species. The impact of the two scenarios (uniformly and non‐uniformly changing winter temperature) on the date of leaf unfolding and on the probability of freezing temperature around that date was evaluated. To test the importance of adaptation to local climate, hypothetical provenance transfers were analysed. It was concluded that, for tree species in The Netherlands and Germany, the probability of spring frost damage will decrease. The contradictory results found in the literature could be ascribed to differences between provenances adapted to their local climate, and is not because different models and different climatic warming scenarios were used in these studies.
Water uptake regulation in peach trees with split‐root systems
Authors: SIMONNEAU T. , HABIB R. 
Published: April 2006

ABSTRACTThe water uptake of 3‐ to 4‐year‐old peach trees ‘May‐crest/Prunus Damas’ grown in an aerated nutrient solution was studied using a split‐root system. Each container and the whole tree were weighed independently to measure water absorption by both parts of the root system and tree transpiration. Water potential of leaves was measured with a pressure chamber. Water potential of roots was estimated using root suckers sealed in plastic bags before the measurement. The nutrient solution was removed from one container so that half the root system was left in humid air for 48 h. Water potential of roots left in solution decreased, which (partly) maintained water absorption and thus transpiration. No modification of root hydraulic resistance was required to simulate the experimental results. Nevertheless, enhancement of absorption by the roots supplied with solution cannot compensate for the water loss by transpiration. Depletion of water from the plant essentially came from the non‐absorbing roots. This was demonstrated by substituting vegetable oil for nutrient solution around one half of the split‐root system, and by following the changes in root volume on the basis of Archimedes principle. Conflicting results in the literature about apparent changes in hydraulic resistance are discussed.
Reversing cavitation in tracheids of Pinus sylvestris L. under negative water potentials
Authors: EDWARDS W. R. N. , JARVIS P. G. , GRACE J. , MONCRIEFF J. B. 
Published: April 2006

ABSTRACTXylem cavitation is a frequent event, but since resistance to flow does not generally increase in vivo, reversal must also occur even under negative potentials. We demonstrated that this can occur in excised wood. Our results suggest that refilling of cavitated tracheids at negative water potentials may result from a change in equilibrium between gas concentrations, water potential and surface tension at the embolism interface. Excised branch‐wood specimens from small trees of Pinus sylvestris were dried on the bench to a range of relative water contents and then rehydrated in a permeability apparatus using ultra‐filtered, de‐aerated water as permeant. Water inflow and outflow were measured gravimetrically by recording the gain or loss from two reservoirs held on balances. Flow was induced through the specimen by holding the balances at different levels, while an overall negative water potential could be imposed by raising the specimen above the inflow/outflow reservoirs. Changes in water content of the specimen were calculated as the difference between inflow and outflow. The time‐course data for both relative water content and permeability were fitted to an exponential function to give initial and final estimates and a time constant. Rehydration occurred at all imposed water potentials, but the speed of recovery was affected at lower potentials. Where drying of the specimen was more protracted, permeability was initially lower but also recovered during permeation. Both flow and de‐aeration were necessary for complete rehydration. A model requiring new information on gas concentrations and transport coefficients is suggested.
The influence of elevated CO2 on non‐structural carbohydrate distribution and fructan accumulation in wheat canopies
Authors: SMART D. R. , CHATTERTON N. J. , BUGBEE B. 
Published: April 2006

ABSTRACTWe grew 2.4 m2 wheat canopies in a large growth chamber under high photosynthetic photon flux (1000 μmol m−2 s−1) and using two CO2 concentrations, 360 and 1200 μmol mol−1. Photosynthetically active radiation (400–700 nm) was attenuated slightly faster through canopies grown in 360μmol mol−1 than through canopies grown in 1200μmol mol−1, even though high‐CO2 canopies attained larger leaf area indices. Tissue fractions were sampled from each 5‐cm layer of the canopies. Leaf tissue sampled from the tops of canopies grown in 1200μmol mol−1 accumulated significantly more total non‐structural carbohydrate, starch, fructan, sucrose, and glucose (p≤ 0.05) than for canopies grown in 360μmol mol−1. Non‐structural carbohydrate did not significantly increase in the lower canopy layers of the elevated CO2 treatment. Elevated CO2 induced fructan synthesis in all leaf tissue fractions, but fructan formation was greatest in the uppermost leaf area. A moderate temperature reduction of 10 °C over 5d increased starch, fructan and glucose levels in canopies grown in 1200μmol mol−1, but concentrations of sucrose and fructose decreased slightly or remained unchanged. Those results may correspond with the use of fructosyl‐residues and release of glucose when sucrose is consumed in fructan synthesis.
Root elongation rate is accounted for by intercepted PPFD and source‐sink relations in field and laboratory‐grown sunflower
Authors: AGUIRREZABAL L. A. N. , DELEENS E. , TARDIEU F. 
Published: April 2006

ABSTRACTThe existence of relationships between intercepted photo‐synthetic photon flux density (PPFD) and growth of individual organs is somewhat controversial. We have tested whether such relationships could account for the natural variability in elongation rates of taproot and secondary roots of sunflower (from 2 to 135 mm d−1), in field and laboratory conditions. Elongation of taproot and secondary roots was recorded daily through windows in the field. A range of PPFD was obtained by following day‐to‐day natural fluctuation for three contrasting growing periods, and by shading part of the plants under study. A parallel experiment was carried out in a growth chamber with contrasting light intensities and with a 14CO2 labelling experiment. After the two‐leaf stage, i.e. when the contribution of photosynthetic carbon became appreciable in root growth, daily root elongation rate was closely linked to the PPFD intercepted from 36 to 12 h before the measurement of root elongation. Curvilinear relationships applied to plants grown in the field as well as in a growth chamber, and to shaded plants as well as to plants subjected to day‐to‐day changes in intercepted PPFD. For a given intercepted PPFD, the taproot elongated faster than secondary roots, and secondary roots originating near the base of the taproot elongated faster than those originating near the apex. The elongation rate of any secondary root apex was accounted for (r= 0.77) by the ratio of intercepted PPFD to the distance between the apex and the base of the taproot. No relationships between intercepted PPFD and elongation rate were observed before the two‐leaf stage, when the CO2 labelling experiment suggests that carbon essentially originates from the seed. Therefore, this study suggests a role for source‐sink relations in the distribution of elongation between apices and a role for carbon nutrition in day‐to‐day variations of root elongation rate. Precise mechanisms explaining this behaviour remain to be investigated.
Redox characteristics of normal and habituated cell lines of sugarbeet
Authors: CARRIÉ B. , GASPAR T.H. , GREPPIN H. , PENEL C. 
Published: April 2006

ABSTRACTRedox properties of cells of normal hormone‐requiring (N) and habituated (H) sugarbeet calli have been investigated. It was found that H cells at all ages reduced exogenous ferricyanide at a much higher rate than N cells, but they exhibited a lower chemiluminescence either alone or in presence of luminol. The plasma membrane NADH:fer‐ricyanide oxidoreductase measured in vitro was almost identical for the two cell types. This could indicate that the higher reducing power of H cells had an intracellular origin. Among the enzyme activities which could provide electrons, malate dehydrogenase activity was found to be a good candidate, being more active in H cells. The results are discussed in relation to the abnormal structure of the cell wall of habituated cells.
Scaling sun and shade photosynthetic acclimation ofAlocasia macrorrhizato whole‐plant performance – II. Simulation of carbon balance and growth at different photon flux densities
Authors: SIMS D.A. , GEBAUER R.L.E. , PEARCY R.W. 
Published: April 2006

ABSTRACTA whole‐plant carbon balance model incorporating a light acclimation response was developed forAlocasia macrorrhizabased on empirical data and the current understanding of light acclimation in this species. The model was used to predict the relative growth rate (RGR) for plants that acclimated to photon flux density (PFD) by changing their leaf type, and for plants that produced only sun or shade leaves regardless of PFD. The predicted RGR was substantially higher for plants with shade leaves than for those with sun leaves at low PFD. However, the predicted RGR was not higher, and in fact was slightly lower, for plants with sun leaves than for those with shade leaves at high PFD. The decreased leaf area ratios (LARs) of the plants with sun leaves counteracted their higher photosynthetic capacities per unit leaf area (Amax). The model was manipulated by changing parameters to examine the sensitivity of RGR to variation in single factors. Overall, RGR was most sensitive to LAR and showed relatively little sensitivity to variation inAmaxor maintenance respiration. Similarly, RGR was relatively insensitive to increases in leaf life‐span beyond those observed. Respiration affected RGR only at low PFD, whereasAmaxwas moderately important only at high PFD.