bluuebunny/crossref_metadata_2025_split huggingface dataset:
A model of stomatal conductance to quantify the relationship between leaf transpiration, microclimate and soil water stress
Authors: Gao Q. , Zhao P. , Zeng X. , Cai X. , Shen W. 
Published: March 2003

AbstractA model of stomatal conductance was developed to relate plant transpiration rate to photosynthetic active radiation (PAR), vapour pressure deficit and soil water potential. Parameters of the model include sensitivity of osmotic potential of guard cells to photosynthetic active radiation, elastic modulus of guard cell structure, soil‐to‐leaf conductance and osmotic potential of guard cells at zero PAR. The model was applied to field observations on three functional types that include 11 species in subtropical southern China. Non‐linear statistical regression was used to obtain parameters of the model. The result indicated that the model was capable of predicting stomatal conductance of all the 11 species and three functional types under wide ranges of environmental conditions. Major conclusions included that coniferous trees and shrubs were more tolerant for and resistant to soil water stress than broad‐leaf trees due to their lower osmotic potential, lignified guard cell walls, and sunken and suspended guard cell structure under subsidiary epidermal cells. Mid‐day depression in transpiration and photosynthesis of pines may be explained by decreased stomatal conductance under a large vapour pressure deficit. Stomatal conductance of pine trees was more strongly affected by vapour pressure deficit than that of other species because of their small soil‐to‐leaf conductance, which is explainable in terms of xylem tracheids in conifer trees. Tracheids transport water by means of small pit‐pairs in their side walls, and are much less efficient than the end‐perforated vessel members in broad‐leaf xylem systems. These conclusions remain hypothetical until direct measurements of these parameters are available.
Measurement of xylem sap amino acid concentrations in conjunction with whole tree transpiration estimates spring N remobilization by cherry (Prunus avium L.) trees
Authors: GRASSI G. , MILLARD P. , WENDLER R. , MINOTTA G. , TAGLIAVINI M. 
Published: March 2003

Abstract Prunus avium trees were grown in sand culture for one vegetative season with contrasting N supplies, in order to precondition their N storage capacities. During the spring of the second year a constant amount of 15N was supplied to all the trees, and the recovery of unlabelled N in the new biomass production was used as a direct measure of N remobilization. Destructive harvests were taken during spring to determine the pattern of N remobilization and uptake. Measurements of both xylem sap amino acid profiles and whole tree transpiration rates were taken, to determine whether specific amino acids are translocated as a consequence of N remobilization and if remobilization can be quantified by calculating the flux of these amino acids in the xylem. Whereas remobilization started immediately after bud burst, N derived from uptake by root appeared in the leaves only 3 weeks later. The tree internal N status affected both the amount of N remobilization and its dynamics. The concentration of xylem sap amino acids peaked shortly after bud burst, concurrently with the period of fastest remobilization. Few amino acids and amides (Gln, Asn and Asp) were responsible for most of N translocated through the xylem; however, their relative concentration varied over spring, demonstrating that the transport of remobilized N occurred mainly with Gln whereas transport of N taken up from roots occurred mainly with Asn. Coupling measurements of amino acid N in the xylem sap with transpiration values was well correlated with the recovery of unlabelled N in the new biomass production. These results are discussed in relation to the possibility of measuring the spring remobilization of N in field‐grown trees by calculating the flux of N translocation in the xylem.
Effects of timing of Leptosphaeria maculans ascospore release and fungicide regime on phoma leaf spot and phoma stem canker development on winter oilseed rape (Brassica napus) in southern England
Authors: West J. S. , Fitt B. D. L. , Leech P. K. , Biddulph J. E. , Huang Y.‐J. , Balesdent M.‐H. 
Published: March 2003

At Rothamsted during 1997/98, 1998/99 and 1999/2000 winter oilseed rape growing seasons, numbers of air‐borne ascospores of Leptosphaeria maculans were often > 4 m−3 from autumn (September/October) to spring (April/May), while few or no ascospores were detected during the summer. Mature pseudothecia were generally not observed on debris of the previous crop until September. One‐year‐old debris (harvested in July 1998) had 95% discharged and 5% mature pseudothecia in August 1999, but by 15 September new pseudothecia (of which 30% were mature) were observed and the first increase in air‐borne ascospores (> 4 m−3) occurred. Phoma leaf spotting appeared in untreated field plots 14–25 days after the first increase in air‐borne ascospores in autumn. The fungicide mixture difenoconazole plus carbendazim decreased the incidence of new leaf lesions for 1 month after application in autumn and for 2 months in mid‐winter. When L. maculans was isolated from infected leaves, the growth rate of isolates from leaves to which fungicide was applied was less than that of those from untreated leaves. Foliar applications of fungicide to field plots in the autumn and winter not only decreased the incidence of crown cankers but also reduced the rate of canker development on stem bases in the spring and early summer (when severity of crown cankers increased linearly with time). In untreated crops, when phoma leaf spots appeared early in the autumn, crown cankers developed early in the spring but only became severe enough before harvest to reduce yield greatly in 1997/98. Yield loss was associated with crown cankers that girdled more than half of the stem by harvest (mean severity > 3 on a 0–5 scale). Infections of new leaves produced after stem extension, from January onwards, led to phoma stem lesion development above the crown. In the three seasons, phoma stem lesions became moderately severe (> 2) by harvest only in untreated plots in 1997/98.
Potential of sexual reproduction among host‐adapted populations of Phytophthora infestans sensu lato in Ecuador
Authors: Oliva R. F. , Erselius L. J. , Adler N. E. , Forbes G. A. 
Published: March 2003

To determine the potential of sexual reproduction among host‐adapted populations of Phytophthora infestans sensu lato in Ecuador, 13 A1 isolates belonging to clonal lineages US‐1, EC‐1 and EC‐3, and 11 A2 isolates belonging to the clonal lineage EC‐2, were paired on agar plates to induce crossing. In the first experiment, six A1 isolates (three US‐1, two EC‐1 and one EC‐3) were each crossed with three A2 isolates (total = 18 crosses). Matings involving isolates of the EC‐1 lineage produced more oospores of healthy appearance than did matings with isolates of US‐1 or EC‐3. In the second experiment, the oospores of 35 crosses (21 EC‐1 × EC‐2; 10 US‐1 × EC‐2; four EC‐3 × EC‐2) were dispersed on water agar to assess oospore germination. Overall, germination percentages were low. Only one cross produced enough progeny for evaluation. Twenty‐three single‐oospore offspring were isolated and evaluated for mating type; electrophoretic patterns of glucose‐6‐phosphate isomerase (Gpi) and peptidase (Pep) alloenzyme loci; mitochondrial DNA haplotype; and genomic DNA fingerprint. Multilocus genotype data indicated that all 23 isolates resulted from meiotic recombination. Four progeny with homothallic phenotype appeared to be unstable heterokaryons. Markers at several loci segregated according to simple Mendelian expectations for a diploid organism, but the ratios of three RFLP loci and the Pep locus were not consistent with Mendelian expectations. All progeny were nonpathogenic on hosts of the parental genotypes. Reduced mating success and reduced pathogenic fitness of progeny appear to be postmating mechanisms of reproductive isolation in populations of P. infestans sensu lato in Ecuador.
Factors affecting mummification and sporulation of pome fruit infected by Monilinia fructigena in Dutch orchards
Authors: Van Leeuwen G. C. M. , Holb I. J. , Jeger M. J. 
Published: March 2003

A 2‐year field experiment (1997–98, 1998–99) was conducted to study mummification and subsequent sporulation in spring of apple (cvs James Grieve, Golden Delicious) and pear (cv. Conference) fruits infected by Monilinia fructigena. Most mummified fruits were found in James Grieve and Conference, whereas in late‐infected Golden Delicious, fruits were still soft when examined in April. In the first year, these late‐infected fruits had a significantly higher sporulation intensity per sporulating fruit (P = 0·05) compared with Golden Delicious fruits infected 9 and 5 weeks before harvest maturity, which were partly mummified. It was concluded that early‐ and late‐infected fruits contributed to primary inoculum in the next season. In a postinfection regime of 25°C and 65–75% relative humidity under controlled conditions, the number of Conference fruits sporulating decreased rapidly, and after 12 weeks’ incubation sporulation had completely ceased. After 8 weeks’ incubation, sporulation intensity in the postinfection regime at 10°C was significantly higher than that at 20 and 25°C in a first experiment with inoculated unripe fruit (P = 0·05). Results of a second experiment with ripe fruit were less clear. These results are discussed in relation to orchard disease management.
Hydromagnesite replacement of biomineralized aragonite in a new location of Holocene stromatolites, Lake Walyungup, Western Australia
Authors: COSHELL L. , ROSEN M. R. , MCNAMARA K. J. 
Published: March 2003

Holocene stromatolites are described from Lake Walyungup, a coastal hyposaline lake in south‐western Australia. At summer low water, this groundwater‐fed depression comprises two permanent shallow water bodies and an ephemeral southern pool, set within an areally extensive littoral zone of variably cemented carbonate crust. Up to 5 m of organic‐rich carbonate mud has been deposited within each of these basins in less than 7000 years. Stromatolites rim the water bodies with individual columns up to 2 m tall. Stromatolite‐capped tepee structures in subparallel alignment are widespread in the littoral crust, suggesting a linkage between stromatolite growth and zones of groundwater discharge. Lake Walyungup stromatolites, regardless of external morphology and setting, are coarsely laminated and have aragonitic mesoclot microfabrics. These microfabrics are similar to those from lithified portions of active thrombolitic microbialites from nearby Lake Clifton.Hydromagnesite is a minor to subdominant phase (up to 47 wt%) of the carbonate mineral assemblage in Lake Walyungup. It occurs mainly in the littoral zone as a diagenetic replacement of precursor aragonite, particularly within the mesoclot fabric of stromatolites, but also in sediments (strandline and dune sand, crusts) derived mainly from erosion of stromatolites. In contrast with nonreplaced and impermeable inorganic aragonitic cements, stromatolite mesoclots are microper‐ meable. Micropermeability is inferred to facilitate hydromagnesite diagenesis. Dolomite is also present in minor amounts as a pore fill in stromatolites, and as a subdominant to dominant (up to 100 wt%) phase in thin, mudcracked micrite layers within the crust package. The layered dolomite may be precipitated directly from the lake water.Major element abundance of the lake water is: Na+ > Mg2+ » K+ > Ca2+ for cations, and Cl− » SO42− ≈ HCO3− > CO32− for anions. Compared to other nearby coastal lakes, Lake Walyungup has a high pH (> 9·0), and an extremely high molar Mg/Ca ratio of > 90. Groundwater in the area has a Mg/Ca ratio generally less than 1. The unusual Mg/Ca ratio in Lake Walyungup is partially a result of in‐lake processes with additional minor contribution of Mg2+ sourced from basal marine sand because no Mg‐rich bedrock source has been found in the region.
Morphological variation and mating compatibility within the mealybugs Pseudococcus calceolariae and P. similans (Hemiptera: Pseudococcidae), and a new synonymy
Authors: Charles John G. , Froud Karyn J. , Henderson Rosa C. 
Published: March 2003

SummaryA laboratory study of isolines of Pseudococcus calceolariae (Maskell) and P. similans (Lidgett) collected from Hawke's Bay and Auckland, two widely separated regions in the North Island of New Zealand, threw doubt on the validity of the defining characters of these species. For P. similans, the number and position of oral rim tubular ducts varied widely and sometimes fell outside the defined limits for the species, and characteristic ‘stout abdominal setae’ were lost in the F1 generation. The morphological characters that separate one species from the other were manipulated by changing the temperature at which the mealybugs developed, such that cohorts of F1 sisters reared in the laboratory contained phenotypes of both P. calceolariae and P. similans. No impediments were found to breeding among populations of P. calceolariae and P. similans from Hawke's Bay and Auckland. All combinations of crosses between virgin females and males produced viable progeny. Those reared at 16°C laid more eggs than those reared at 23°C. The data did not suggest the existence of cryptic or sibling species, and contrasted with experiments elsewhere which quite clearly showed species incompatibility of closely related mealybugs. Examination of 160 ‘wild’ specimens of P. calceolariae from New Zealand, Australia and California (U.S.A.) and P. similans from New Zealand and Australia showed a morphological continuum from one species to the other. It is concluded that P. calceolariae and P. similans merely represent the phenotypic extremes of one widely polymorphic species, with the morphological characters of individual adults determined by the microenvironment in which they developed. Pseudococcus calceolariae is thus the senior synonym of P. similans.
Identification and molecular mapping of a single Arabidopsis thaliana locus determining resistance to a phytopathogenic Pseudomonas syringae isolate
Authors: Debener Thomas , Lehnackers Hiltrud , Arnold Martin , Dangl Jeffery L 
Published: March 2003

SummaryWe present a model pathosystem to dissect genetically the disease resistance response of plants against phytopathogenic bacteria. The interaction between Pseudomonas syringae pathovar maculicola (Psm) and Arabidopsis thaliana displays phenotypic variaion which depends on the genotype of both partners. Compatible interactions are defined by sustained inplanta bacterial growth and are normally accompanied of their appearance. For compatible interactions, resistance is defined by limited in‐planta bacterial growth accompanied by a typical ‘hypersensitive response’ (HR). We show that at least parts of this system fit the paradigms of Flor’s ‘gene‐for‐gene’ hypothesis. We identify functionally a putative bacterial avirulence gene (avrRpm 1) from a Psm isolate which conditions the HR on A. thaliana ecotypes Oy‐0 abd Col‐ 0, but not Nd‐0. We also demonstrate that resistance to the Psm strain from which avrRpm1 was isolated segregates as a single trait in the crosses Col‐o x Nd‐0 and Nd‐0 x Oy‐0. Furthermore, we map this locus (RPM1) molecularly in the Col‐0 x Nd‐0 cross to a relatively small interval defined by two RFLP markers on A. thliana chromosome 3. Resistance in the second cross also maps to this locus and cosegregates with resistance to avrRpm1.
Molecular analyses of a barley multigene family homologous to the yeast protein kinase gene SNF1.
Authors: Halford NG , Vicente‐Carbajosa J , Sabelli PA , Shewry PR , Hannappel U , Kreis M 
Published: March 2003

SummaryGenomic sequences homologous to the yeast gene SNF1 have been isolated from barley (Hordeum vulgare) cv. Sunbar. SNF1 encodes a protein serine/threonine kinase required for the derepression of a number of genes, including SUC2 (invertase) in response to glucose deprivation. Southern blotting showed the presence of a family of related genes in barley and full‐length sequences have been determined for two members of the family, one of which lacks an exon and is almost certainly non‐ functional. A partial sequence has been obtained for a third member of the family. The transcription start site of one of the genes has been determined by S1 nuclease protection. A transcript almost identical in sequence to the exons of one of the genes has been amplified from barley endosperm mRNA using the polymerase chain reaction. One of the full‐length genomic sequences contains nine introns and 10 exons and the number and position of the introns in the second full‐length sequence is identical except that it lacks exon 2. However, the length and sequence of the introns vary. Northern blot analyses indicated that related transcripts are present in aleurones, coleoptiles, endosperms, internodes, leaves, ovules, roots and root tips, with highest levels of expression in the aleurones and endosperms.
Efficient initiation of translation at non‐AUG triplets in plant cells.
Authors: Gordon K , Futterer J , Hohn T 
Published: March 2003

SummaryThe efficiency of translation initiation at triplets differing at one residue from AUG was tested by transient expression in protoplasts from two different plant species. All possible alternative codons were tested. Some triplets showed significant CAT activity, with CUG (30% of the AUG activity) being most active. Most others had between 5 and 15% of the activity obtained from AUG, whereas UUG and AUC yielded about 2% and the two composed only of purines, AAG and AGG, had no significant activity. Translation initiation from AUC, especially, responded to leader sequences outside the immediate context which did not affect translation initiation from AUG.
Metabolic regulation of rice α‐amylase and sucrose synthase genes in planta
Authors: Karrer Erik E. , Rodriguez Raymond L. 
Published: March 2003

SummaryIsolated rice embryos were used to investigate the regulatory effects of endosperm extracts and pure sugars on the expression of α‐amylase gene RAmy3D and a sucrose synthase gene homologous to the maize isozyme Ss2. The high‐level expression of RAmy3D in the scutella of isolated embryos could be inhibited by a variety of sugars as well as endosperm extracts from germinated rice grains. Glucose, at a concentration of 250 mM, was most effective in repressing RAmy3D mRNA accumulation. Furthermore, this repression was reversible. Interestingly, RAmy3D repression was always accompanied by the induction of sucrose synthase gene expression. These results support a model in which the expression of α‐amylase and sucrose synthase genes in the rice scutellum are counter‐regulated by the influx of sugars from the endosperm.
A Brassica napus gene family which shows sequence similarity to ascorbate oxidase is expressed in developing pollen. Molecular characterization and analysis of promoter activity in transgenic tobacco plants
Authors: Albani Diego , Sardana Ravinder , Robert Laurian S. , Altosaar Illimar , Arnison Paul G. , Fabijanski Steven F. 
Published: March 2003

SummaryThe genomic clone named Bp 10 contains a member of a small pollen‐specific gene family of B. napus. The expression of the Bp 10 gene family is maximal in early binucleate microspores and declines considerably in mature trinucleate pollen. Homologues of the Bp 10 genes are expressed in the pollen of other plant species. The pollen‐specific expression of the gene contained in the genomic clone was confirmed in tobacco plants transformed with a chimeric Bp 10 promoter/GUS construct. A promoter fragment of 396 bp is sufficient to direct a strong and correct spatial and temporal expression in transgenic plants. The Bp 10 gene family codes for proteins of 62 kDa showing approximately 30% sequence identity to cucumber and pumpkin ascorbate oxidases (AAOs). However, the AAO active centres are not conserved in the Bp 10 products, suggesting an evolutionary relationship but a different enzymatic activity for these proteins. Expression of a recombinant Bp 10 protein in E. coli inhibits bacterial growth on minimal medium, suggesting the production of an enzymatically active polypeptide in bacteria. No AAO activity could be correlated with the expression of the recombinant protein. Moreover, substances affecting AAO activity do not appear to influence the inhibitory activity of the protein produced in bacteria. However, as indicated by the rescue of bacterial growth in the presence of sodium bicarbonate or gaseous CO2, the Bp 10 protein activity could be modulated by CO2 levels.
Co‐assembly properties of higher plant microtubule‐associated proteins with purified brain and plant tubulins
Authors: Schellenbaum Paul , Vantard Marylin , Peter Christine , Fellous Arlette , Lambert Anne‐Marie 
Published: March 2003

SummaryThe knowledge of higher plant microtubule‐associated proteins (MAPs) remains limited to a few examples that illustrate essentially their binding properties to preformed microtubules as described in carrots. Using taxol‐stabilized microtubules a putative MAP‐enriched fraction has been isolated in maize cultured cell extracts, one of these polypeptides is immunologically related to neural tau. At present, these proteins are being characterized by co‐assembly assays that were not possible before. Similar experiments were done also in a heterologous system using brain tubulin. Three polypeptides out of seven that constituted the MAP fraction were found to co‐assemble specifically with tubulin subunits of both origins. Their apparent molecular weights are 67, 83 and 125 kDa. A two‐dimensional gel immunoblot of the 83 kDa polypeptide with tau antibodies revealed one major spot. Polypeptides were quantiated by scanning the gels. These results shed light on the present debate on higher plant MAPs and their potential activity in the regulation of microtubule assembly and function in the higher plant cell.