bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correspondence between rates of host plant consumption and responses to the Acalymma vittatum male‐produced aggregation pheromone
Authors: Smyth Rebecca R. , Hoffmann Michael P. 
Published: March 2003

Abstract In field studies, wind‐directed traps were used to investigate the resource‐based properties of the male‐produced aggregation pheromone of Acalymma vittatum (F.) (Coleoptera: Chrysomelidae). Responses to early season overwintered field‐collected male A. vittatum without food were compared with those feeding on pollen, and in turn these were compared with those feeding on cucurbit seedlings. These comparisons were modelled after transitions as they would occur at the initiation of A. vittatum host plant colonization.In another experiment, colony‐reared male A. vittatum that had been fed only near isogenic lines of potted cucumber (Cucumis sativus) seedlings that either lacked or contained cucurbitacin were placed as bait in the traps. Using the inverse relationship, which is understood for A. vittatum, between previous exposure and the phagostimulant response to cucurbitacin, rates of foliage consumption could be manipulated. The interaction between relative rates of host plant consumption of the males used as lures and responses to the pheromone could thus be tested. The use of A. vittatum reared entirely without dietary cucurbitacin as bait also enabled evaluation of the potential role of cucurbitacin in pheromone biosynthesis. Trap responses were closely correlated with the rates of feeding of the beetles in the trap lures, but cucurbitacin was neither a precursor nor a prerequisite for the pheromone. Implications for early season field colonization and the adaptive significance of this pheromone are discussed.
Relating genotype and phenotype for tryptophan synthesis in an aphid–bacterial symbiosis
Authors: Birkle L. M. , Minto L. B. , Douglas A. E. 
Published: March 2003

Abstract.The symbiotic bacteria Buchnera provide their aphid hosts with tryptophan and other essential amino acids. Tryptophan production by Buchnera varied among 12 parthenogenetic clones of the pea aphid Acyrthosiphon pisum (Harris), as determined from both the incorporation of radioactivity from 14C‐anthranilate into tryptophan and the protein‐tryptophan growth rate of larval aphids on tryptophan‐free diet. The values of tryptophan production obtained for the two methods were correlated significantly with each other but not with the level of amplification of the Buchnera genes trpEG, which code for anthranilate synthase, a key enzyme in tryptophan biosynthetic pathway. This study provides the first direct demonstration of interclonal variation in production of any nutrient in an aphid–Buchnera symbiosis and indicates that a key aspect of Buchnera phenotype (tryptophan production) does not vary in a simple fashion with Buchnera genotype.
Effect of external oxygen demand on radial oxygen loss by Juncus roots in titanium citrate solutions
Authors: Sorrell B. K. 
Published: March 2003

ABSTRACTRadial oxygen loss (ROL) from the roots of two semiaquatic rushes, Juncus effusus L. and Juncus inflexus L., was studied in reducing titanium citrate buffer, using both closed incubations and a flow‐through, titrimetric system. In closed experiments, roots released oxygen at a constant rate over a wide range of external oxygen demands, with the ROL rate only depending on sink strength at low demands, and no oxygen release into oxidized solutions. In the titrimetric experiments, roots continued to release oxygen at constant rates when provided with a constant external oxygen demand. ROL was higher in J. effusus (9·5 ± 1 × 10−7 mol O2 h−1 root−1) than in J. inflexus (4·5 ± 0·5 × 10−7 mol O2 h−1 root−1). Light and dark changes around the shoots did not affect the ROL rate in J. inflexus, whereas in J. effusus ROL was ≈ 1·75 times higher in the light than in the dark, presumably due to changes in stomatal aperture. These results suggest that ROL is controlled by the external oxygen demand at low to moderate reducing intensities, but that structural limitations to oxygen diffusion rates prevent ROL from continuing to increase at higher external oxygen demands.
Accumulation of an apoplastic solute in the guard‐cell wall is sufficient to exert a significant effect on transpiration in Vicia faba leaflets
Authors: Ewert M. S. , Jr W. H. Outlaw , Zhang S. , Aghoram K. , Riddle K. A. 
Published: March 2003

ABSTRACTAccumulation of recently photosynthesized sucrose in the guard‐cell wall is the empirical foundation for a hypothesis that links the rates of photosynthesis, translocation, and transpiration (Plant Physiology 114, 109–118). Critical assumptions of this hypothesis were tested by use of Vicia faba, an apoplastic phloem loader. Following measurements of the leaflet‐apoplastic‐water volume (by P–V isotherm analysis) and the guard‐cell wall volume (by 3‐D analysis), intact leaflets were fed dilute solutions of mannitol, an impermeant non‐toxic osmolyte. Even at bulk‐leaflet mannitol concentrations that would have only a negligible osmotic effect on stomata, transpiration at constant temperature, water‐vapour pressure, air movement and irradiance was diminished up to 25%, compared with controls. This effect on transpiration, a manifestation of smaller stomatal aperture size, was explained by accumulation of mannitol, up to 350 mol m−3, in the estimated aqueous volume of the guard‐cell wall. The conclusion is that mannitol, a xenobiotic with structural similarity to sucrose, can move throughout the apoplast of a transpiring leaflet and accumulate in an osmotically significant concentration in the guard‐cell wall. These data therefore provide support for a new role for sucrose as a signal metabolite that integrates essential functions of the whole leaf. In addition, the results raise questions about the physiological or experimental accumulation of other guard‐cell‐targeted apoplastic solutes such as plant growth regulators, particularly abscisic acid, and ions.
Electrical resistance changes during exposure to low temperature measure chilling and freezing tolerance in olive tree (Olea europaea L.) plants
Authors: Mancuso S. 
Published: March 2003

ABSTRACTElectrical resistance changes in different organs of four olive tree (Olea europaea L.) varieties, characterized by different tolerance to chilling and freezing, were examined, during exposure to low temperature. Apparent critical temperatures (CT) and freezing temperatures (Tfr) were identified on the basis of the electrical resistance changes. Both temperatures were lower for the more chilling‐tolerant genotypes. From the apparent critical temperatures, the absolute critical temperature (CTabs) and the time delay of the chilling signal transduction process were calculated. In shoots, CTabs varied from 8·8 °C for Ascolana (chilling‐tolerant variety) to 13·6 °C for Coratina (chilling‐sensitive variety). The magnitude of the transduction time was very similar (about 2 min) for the three genotypes that are more sensitive to chilling, whereas it was significantly higher (about 3 min) for the most tolerant genotype. Different freezing temperatures were observed for different organs. It would appear from this experiment that the order of sensitivity is roots > leaves > shoots > vegetative buds. Accord was found between the absolute critical temperature of electrical resistance and the critical temperature of membrane potential. The occurrence of electrical resistance changes in the tissues of the olive trees exposed to low temperature suggests the use of this experimental procedure as a quick, easy and non‐destructive tool to screen plant tissues for chilling tolerance. The strong dependence of the electrical resistance on low temperature, and the critical temperature of around 10 °C, can yield interesting information about the lowest thermal limits for the continuation of normal physiological processes and therefore about the adaptability of plants to particular environments.
Relative humidity‐ and ABA‐induced variation in carbon and oxygen isotope ratios of cotton leaves
Authors: Barbour M. M. , Farquhar G. D. 
Published: March 2003

ABSTRACTCotton (Gossypium hirsutum L. cv. CS50) plants were grown at two levels of relative humidity (RH) and sprayed daily with abscisic acid (ABA) at four concentrations. Plants grown at lower humidity had higher transpiration rates, lower leaf temperatures and lower stomatal conductance. Plant biomass was also reduced at low humidity. Within each humidity environment, increasing ABA concentration generally reduced stomatal conductance, evaporation rates, superficial leaf density and plant biomass, and increased leaf temperature and specific leaf area. As expected, decreased stomatal conductance resulted in decreased carbon isotope discrimination in leaf material (Δ13Cl). Plants grown at low humidity were more enriched in 18O than those grown at high RH, as theory predicts. Within each humidity environment, increasing ABA concentration increased oxygen isotope enrichment of leaf cellulose (Δ18Oc) and whole‐leaf tissue (Δ18Ol). Values of Δ13Cl and Δ18Ol predicted by theoretical models were close to those observed, accounting for 79% of the measured variation in Δ13Cl and 95% of the measured variation in Δ18Ol. Supporting theory, Δ13Cl and Δ18Ol in whole‐leaf tissue were negatively related.
The Arabidopsis thaliana ATP‐binding cassette proteins: an emerging superfamily
Authors: Davies T. G. E. , Coleman J. O. D. 
Published: March 2003

ABSTRACTSolute transport systems are one of the major ways in which organisms interact with their environment. Typically, transport is catalysed by integral membrane proteins, of which one of the largest groups is the ATP‐binding cassette (ABC) proteins. On the basis of sequence similarities, a large family of ABC proteins has been identified in Arabidopsis. A total of 60 open reading frames (ORFs) encoding ABC proteins were identified by BLAST homology searching of the nuclear genome. These 60 putative proteins include 89 ABC domains. Based on the assignment of transmembrane domains (TMDs), at least 49 of the 60 proteins identified are ABC transporters. Of these 49 proteins, 28 are full‐length ABC transporters (eight of which have been described previously), and 21 are uncharacterized half‐transporters. Three of the remaining proteins identified appear to be soluble, lacking identifiable TMDs, and most likely have non‐transport functions. The eight other ORFs have homology to the nucleotide‐binding and transmembrane components of multi‐subunit permeases. The majority of ABC proteins found in Arabidopsis can, on the basis of sequence homology, be assigned to subfamilies equivalent to those found in the yeast genome. This assignment of the Arabidopsis ABC proteins into easily recognizable subfamilies (with distinguishable subclusters) is an important first step in the elucidation of their functional role in higher plants.
Hydraulic architecture and water relations of Spartium junceum branches affected by a mycoplasm disease
Authors: Gullo M. A. Lo , Trifilò P. , Raimondo F. 
Published: March 2003

ABSTRACTPlant water relations, xylem anatomy and the hydraulic architecture of 1‐year‐old twigs of Spartium junceum, both healthy and affected by a phytoplasm disease, were studied. The disease causes twigs to be either shortened (witches broom disease, WBD) or flat (fasciate disease, FD). WBD twigs show a sevenfold increase in total leaf area, smaller and shorter xylem conduits, a higher stomatal conductance (gl) and a decline of minimum leaf water potentials (Ψl) below the turgor loss point. FD twigs had nearly twice the leaf area of the healthy controls as well as high gl values and Ψl values below the turgor loss point. Moreover, significant differences between healthy and affected twigs in stem stomatal conductance (gs) and in the total stem area were recorded. Affected twigs die back under drought stress, which is explained by a pronounced loss of hydraulic conductivity of the infected stems (40 and 60%) in FD and WBD as well as by the unfavourable ratio of weighted conduit radius (Σr4) to total surface area (At), so that the efficiency of the stem in supplying the whole transpiring area with water is strongly reduced.
Seasonal patterns of tissue water relations in three Mediterranean shrubs co‐occurring at a natural CO2 spring
Authors: Tognetti R. , Raschi A. , Jones M. B. 
Published: March 2003

ABSTRACTSeasonal changes in tissue water relations of Erica arborea L., Myrtus communis L. and Juniperus communis L., grown in a Mediterranean environment, were analysed under field conditions over a 12 month period by comparing plants grown in the proximity of a natural CO2 spring (about 700 μmol mol−1 atmospheric CO2 concentration, [CO2]) with plants in ambient conditions. Tissue water relations varied in response to changes in water availability, but the seasonal course of tissue water relations parameters was also related to ontogeny. Tissue water relations of these co‐occurring shrubs were not alike. Osmotic potentials and saturated mass/dry mass ratio were lowest during peak drought stress periods. Diurnal changes in osmotic potential at the point of turgor loss were least early in the season, maximal in mid‐season, and decreased again in autumn. Turgor potentials decreased as drought progressed and were highest in late fall and mid‐winter. Symplastic water fraction was highest in mid‐spring for E. arborea and M. communis and decreased during the summer, while the opposite was observed for J. communis. Common to all species, under elevated [CO2], was an increase of turgor pressure, particularly during the summer months. Other parameters showed species‐specific responses to long‐term elevated [CO2]. In particular, exposure to elevated [CO2] increased osmotic potentials in E. arborea under drought, while the opposite was the case for J. communis. Site differences in predawn to midday shifts were not strong in any of the species. Differences in tissue water relations suggest that the coexistence of these shrubs in the same environment with similar water availability are partially based on differential water relations strategies and water use patterns. Regardless of the mechanisms, growth of these shrubs in elevated [CO2] may be either less, similarly or more affected by drought stress than plants in ambient [CO2] depending on the species and season.
Stomatal conductance and photosynthesis vary linearly with plant hydraulic conductance in ponderosa pine
Authors: Hubbard R. M. , Ryan M. G. , Stiller V. , Sperry J. S. 
Published: March 2003

AbstractRecent work has shown that stomatal conductance (gs) and assimilation (A) are responsive to changes in the hydraulic conductance of the soil to leaf pathway (KL), but no study has quantitatively described this relationship under controlled conditions where steady‐state flow is promoted. Under steady‐state conditions, the relationship betweengs, water potential (Ψ) andKLcan be assumed to follow the Ohm's law analogy for fluid flow. When boundary layer conductance is large relative togs, the Ohm's law analogy leads togs=KL(Ψsoil−Ψleaf)/D, whereDis the vapour pressure deficit. Consequently, if stomata regulate Ψleafand limitA, a reduction inKLwill causegsandAto decline. We evaluated the regulation of ΨleafandAin response to changes inKLin well‐watered ponderosa pine seedlings (Pinus ponderosa). To varyKL, we systematically reduced stem hydraulic conductivity (k) using an air injection technique to induce cavitation while simultaneously measuring Ψleafand canopy gas exchange in the laboratory under constant light andD. Short‐statured seedlings (< 1 m tall) and hour‐long equilibration times promoted steady‐state flow conditions. We found that Ψleafremained constant near − 1·5 MPa except at the extreme 99% reduction ofkwhen Ψleaffell to − 2·1 MPa. Transpiration,gs,AandKLall declined with decreasingk(P< 0·001). As a result of the near homeostasis in bulk Ψleaf,gsandAwere directly proportional toKL(R2> 0·90), indicating that changes inKLmay affect plant carbon gain.
Slow development of leaf photosynthesis in an evergreen broad‐leaved tree,Castanopsis sieboldii: relationships between leaf anatomical characteristics and photosynthetic rate
Authors: Miyazawa S.‐I. , Terashima I. 
Published: March 2003

ABSTRACTChanges in net photosynthetic rate on a leaf area basis and anatomical properties during leaf development were studied in an evergreen broad‐leaved tree,Castanopsis sieboldii andan annual herb,Phaseolus vulgaris. InC. sieboldii, surface area of mesophyll cells facing the intercellular air spaces on a leaf area basis (Smes) was already considerable at the time of full leaf area expansion (FLE). However, surface area of chloroplasts facing the intercellular air spaces on a leaf area basis (Sc), and chlorophyll and Rubisco contents on a leaf area basis increased to attain their maximal values 15–40 d after FLE. In contrast, inP. vulgaris, chloroplast number on a leaf area basis,ScandSmesat 10 d before FLE were two to three times greater than the steady‐state levels attained at around FLE. InC. sieboldii, the internal CO2transfer conductance (gi) slightly increased for 10 d after FLE but then decreased toward the later stages. Limitation of photosynthesis bygiwas only about 10% at FLE, but then increased to about 30% at around 40 d after FLE. The large limitation after FLE bygiwas probably due to the decrease in CO2concentration in the chloroplast caused by the increases in thickness of mesophyll cell walls and in Rubisco content per chloroplast surface area. These results clearly showed that: (1) inC. sieboldii, chloroplast development proceeded more slowly than mesophyll cell expansion and continued well after FLE, whereas inP. vulgaristhese processes proceeded synchronously and were completed by FLE; (2) after FLE, photosynthesis in leaves ofC. sieboldiiwas markedly limited bygi. From these results, it is suggested that, in the evergreen broad‐leaved trees, mechanical protection of mesophyll cells has priority over the efficient CO2transfer and quick construction of the chloroplasts.
Distribution of N, Rubisco and photosynthesis in Pinus pinaster and acclimation to light
Authors: Warren C. R. , Adams M. A. 
Published: March 2003

AbstractThe light–nitrogen hypothesis suggests canopy photosynthesis is maximized when there is a positive relationship between irradiance received by foliage, its nitrogen content (per unit area Narea), and maximum rate of photosynthesis (Amax). Relationships among relative irradiance and Narea, allocation of nitrogen within the photosynthetic apparatus to Rubisco and chlorophyll, and Amax were examined in Pinus pinaster Ait. needles up to 6 years of age. Measurements were made before bud break in August 1998, and in May 1999 after the first ‘winter’ rains. In August, Narea in P. pinaster needles decreased from 5·1 to 5·7 g m−2 in sunlit 1‐year‐old needles to 2·3 g m−2 in shaded 6‐year‐old needles. In May, Narea was 5–40% less but spatial trends were the same. At both sampling dates, Amax was less in old shaded needles compared with young sunlit needles, and was thus consistent with the light–nitrogen hypothesis. Relationships between Narea and Amax were positive at both dates yet varied in strength and form. Allocation of nitrogen within the photosynthetic apparatus was qualitatively consistent with acclimation to light (i.e. Rubisco/Chl decreased with shading), but quantitatively suboptimal with respect to photosynthesis owing to consistent over‐investment in Rubisco. This over‐investment increased with height in the canopy and was greater in May than in August.
Acclimation of leaf respiratory properties in Alocasia odora following reciprocal transfers of plants between high‐ and low‐light environments
Authors: Noguchi K. , Nakajima N. , Terashima I. 
Published: March 2003

AbstractAcclimation of respiration to the light environments is important for a plant’s carbon balance. Respiratory rates of mature leaves of Alocasia odora, a typical shade‐tolerant species, were measured during the night for 14 d after reciprocal transfers between high‐ (330 µ mol m−2 s−1) and low‐light (20 µ mol m−2 s−1) environments. Following the transfer, both the rate of CO2 efflux and that of O2 uptake of A. odora leaves adjusted to the new light environments. The O2‐uptake rates changed more slowly than the CO2‐efflux rates under the new environments. Leaf mass per area also changed after the transfer. We analysed whether substrate availability or ATP‐consumption rates influence the respiratory acclimation. Since the addition of sucrose to leaf segments did not influence the O2‐uptake rates, the change of respiratory substrate availability was not responsible for the respiratory acclimation. The addition of an uncoupler induced increases in the O2‐uptake rates, and the degree of enhancement significantly decreased after the transfer from low to high irradiance. Thus, the change in ATP‐consumption rates was responsible for the changes in respiratory rates in the plants transferred from low to high light. Potential rates of O2 uptake, as measured in the presence of both the substrate and the uncoupler, changed after the transfer, and strongly correlated with the O2‐uptake rates, irrespective of the directions of transfer (r = 0·961). There was a strong correlation between maximal activities of NAD‐isocitrate dehydrogenase and the potential rates of O2 uptake (r = 0·933), but a weaker correlation between those of cytochrome c oxidase and the potential rates (r = 0·689). These data indicate that the changes of light environments altered the respiratory rates via the change of the respiratory ATP demand, and that the altered rates of respiration will induce the changes of the respiratory capacities.
Exudation of carboxylates in Australian Proteaceae: chemical composition
Authors: Roelofs R. F. R. , Rengel Z. , Cawthray G. R. , Dixon K. W. , Lambers H. 
Published: March 2003

AbstractRoots of a wide range of plant species exude carboxylates, such as citrate, into the rhizosphere. In the present study, seedlings of a range of Australian Banksia, Hakea and Dryandra species (Proteaceae) were assayed for their exudation of carboxylates. All of these species (Hakea prostrata, Hakea undulata, Hakea petiolaris, Hakea baxteri, Banksia grandis, Banksia prionotes, Banksia occidentalis and Dryandra sessilis) form cluster roots when grown in nutrient solution with a low phosphate concentration. Exudation of carboxylates was studied for cluster roots and non‐cluster roots separately, and for the entire root system. Cluster roots of these Proteaceae exuded malate, malonate, lactate, acetate, maleate, citrate, fumarate, cis‐ and trans‐aconitate. The relative contributions of each of these carboxylates differed between species. Malate, malonate, lactate, citrate and trans‐aconitate, however, were invariably present in large proportions of total carboxylate exudation. Non‐cluster roots of H. prostrata exuded a spectrum of carboxylates (mainly malonate, lactate and citrate), which differed somewhat from the exudation pattern of cluster roots (mainly malate, malonate, lactate and citrate). The rate of exudation for cluster roots of the seven species was approximately 1·6 nmol g−1 FM s−1, which is considerably higher than that reported for a variety of crop and native species that do or do not form cluster roots. Contrary to what occurs in the cluster roots of Lupinus albus, which release carboxylates accompanied by protons so that the rhizosphere is acidified, the present Proteaceae exude the carboxylates as anions without concomitant proton release. The role of carboxylates in the mobilization of phosphate and other nutrients from soil is discussed.