bluuebunny/crossref_metadata_2025_split huggingface dataset:
Microvascular assembly and cell invasion in chick mesonephros grafted onto chorioallantoic membrane
Authors: Navarro Marc , DeRuiter Marco C. , Carretero Ana , Ruberte Jesús 
Published: March 2003

AbstractEmbryonic tissues, in common with other tissues, including tumours, tend to develop a substantial vasculature when transplanted onto the chorioallantoic membrane (CAM). Studies conducted to date have not examined in any detail the identity of vessels that supply these grafts, although it is known that the survival of transplanted tissues depends on their ability to connect with CAM vessels supplying oxygen and nutrients. We grafted the mesonephros, a challenging model for studies in vascular development, when it was fully developed (HH35). We used reciprocal chick‐quail transplantations in order to study the arterial and venous connections and to analyse the cell invasion from the CAM to the organ, whose degeneration in normal conditions is rapid. The revascularization of the grafted mesonephros was produced by the formation of peripheral anastomoses between the graft and previous host vasculatures. The assembly of graft and CAM blood vessels occurred between relatively large arteries or veins, resulting in chimeric vessels of varying morphology depending on their arterial or venous status. Grafts showed an increased angiogenesis from their original vasculature, suggesting that the normal vascular degeneration of the mesonephros was partially inhibited. Three types of isolated host haemangioblast were identified in the mesonephros: migrating angioblast‐like cells, indicating vasculogenesis, undifferentiated haematopoietic cells and macrophages, which might have been involved in the angiogenesis. Tomato lectin was found to bind activated macrophages in avian embryos.
The late‐glacial at Lac de Creno (Corsica, France): a key site in the western Mediterranean basin
Authors: REILLE M. , GAMISANS J. , de BEAULIEU J.‐L. , ANDRIEU V. 
Published: March 2003

summaryThe lower part (460–650 cm) of a lacustrine sequence from Lac de Creno, Corsica (1310 m) is analysed on the basis of 68 pollen spectra and with the support of 10 14C dates (including nine A.M.S. dates). This sequence, which extends from the end of the Würm to the beginning of the Postglacial, reveals a complete late‐glacial. The absence of forest dynamics during the late glacial Interstadial in Corsica is a real mystery. Pollen data clearly suggest that Pinus laricio (=Pinus nigra Arnold ssp. laricio Maire) and perhaps other tree species did not exist in Corsica at that time.
Water distribution in fungal lesions in the wood of sycamore,Acer pseudoplatanus, determined gravimetrically and using nuclear magnetic resonance imaging
Authors: PEARCE R. B. , FISHER B. J. , CARPENTER T. A. , HALL L. D. 
Published: March 2003

SUMMARYWater contents in healthy xylem, reaction zones (column boundary layers) and decayed wood were determined in sycamore (Acer pseudoplatanusL.) naturally infected by sooty bark disease (Cryptostroma corticale(Ellis & Everh.) Gregory & Waller) or wound‐inoculated withUstulina deusta(Fr.) Petrak. orGanoderma adspersum(Schulz) Donk. Water contents determined gravimetrically were greater in reaction zones than in healthy wood by factors of 1.1–2.1 times. Maps of imageable proton density (M0), essentially equivalent to relative water contents, were also calculated from two independent nuclear magnetic resonance (NMR) imaging (MRI) data sets, acquired fromT1orT2weighted experiments. M0values derived from these, corrected forT2andT1respectively, were in good agreement, and paralleled the results obtained when total water was determined gravimetrically, although the proportional increase inM0in reaction zones (1.3–3.7 times) was greater than the corresponding increase in total water.Living wood saturated with water by vacuum infiltration contained approx. 1.3 times more water, determined gravimetrically, than uninfiltrated wood. The proportional increase inM0was greater (1.8–2.4 times). This was attributable to the alleviation of magnetic susceptibility effects by elimination of the gas‐water interfaces normally present in the uninfiltrated wood. The similarities between infiltrated wood and reaction zone tissues in both total gravimetric water content and NMR‐visible water suggest that the biophysical environment of the water might be similar in both. This is compatible with the hypothesis that in reaction zones the gases normally present in the lumens of empty (dead) xylem fibres are replaced by an aqueous solution of phytoalexin‐like compounds. This has been confirmed by microscopy. The implications of this in relation to antimicrobial defence and xylem function are discussed.Although contrast in NMR images of lesions was predominantly attributable to changes inM0, a decrease in the spin‐spin relaxation time(T2)was seen in the vicinity of some lesions. Spin‐lattice relaxation times (T1) were not altered to the same extent.Results obtained from both early and late stages of decay were much more variable than those from healthy wood or from reaction zones, and reflected both the low water content of decayed wood (and hence poor signal‐to‐noise ratios for NMR data) and the changing physical environment as the wood was degraded.
Effect of habitat disturbance on inoculum potential of ericoid endophytes of Western Australian heaths (Epacridaceae)
Authors: HUTTON B. J. , DIXON K. W. , SIVASITHAMPARAM K. , PATE J. S. 
Published: March 2003

SUMMARYThe presence of host plants was found to be a key determinant of soil infectivity for endophytes of epacrids growing in south–west Australian jarrah forest carrying a sparse epacrid understorey. A comparable Banksia woodland with higher density of epacrids showed more uniform levels of infective endophytes, presumably because of closer overlap of host–supported patches of endophyte. Disturbed sites in jarrah forest, in which topsoil had been recently returned following bauxite mining, initially showed extremely low endophyte infectivity, probably due to disruption of the hyphal network, absence of host plants and/or increased competition from soil micro–organisms antagonistic to the endophytes. As the system stabilized and epacrids recruited and grew, inoculum potential of the soil re–established and by 12 yr it equalled that of adjacent undisturbed native forest. At disturbed sites with sparsely distributed adult members of the Epacridaceae, endophyte inoculum proved to be adequate only directly adjacent to the epacrids and declined steeply to negligible levels at only 40 cm radially distant from a host plant. The significance of live epacrid root systems on survival of endophyte inoculum in Banksia woodland was examined following removal of shoots of adult plants of the endemic epacrid, Leucopogon conostephioides DC, Coincident with demise of roots of the detopped plants, endophyte inoculum potential of closely adjacent soil declined by 50% during the growing season. However, the effect was short lived and infectivity rose the following year to equal that of undisturbed adjacent woodland as mycelial matrices supported by neighbouring epacrids invaded the depleted study areas.
Eleocharis sphacelata: internal gas transport pathways and modelling of aeration by pressurized flow and diffusion
Authors: SORRELL BRIAN K. , BRIX HANS , ORR PHILIP T. 
Published: March 2003

summaryThe ability of diffusive gas transport and pressurized, convective flow to satisfy internal oxygen demands was examined for an aquatic sedge, Eleocharis sphacelata R. Br. Resistances to convection and diffusion through the plant were quantified from anatomical studies of the airspace dimensions, and these were used in mathematical models to calculate the fluxes required to satisfy oxygen demands measured in the tissue. The greatest resistance to diffusion in the underwater tissue was the submerged culm between the waterline and sediment surface (1560 Ms m−3 per m culm length). Resistances of the nodal intercalary meristem (52 Ms m−3) and rhizome internode (34 Ms m−3) were minor. In contrast, resistances to convection were low in the culms (38 MPa s m−3 per m culm length), and higher in the nodal meristems (93 MPa s m−3). The rhizome internodes had large cortical canals with a low convective resistance (0.75 MPa s m−3), and a parallel spongy pith with a very high resistance (518 MPa s m−3) that is probably short‐circuited by convection. The resistance of the submerged culm means that diffusion is inadequate to satisfy oxygen demands in plants growing in >10 cm of water, and that convection is therefore essential in the natural habitat of this species (water to c. 2 m depth). However, a convective oxygen influx as low as 28 × 10−8 mol s−1 per culm (equivalent to a gas flow rate of 3 μl s−1 per culm) could satisfy the entire oxygen demand of the underwater tissue; this value is well below actual rates. At this flow rate, the spongy pith in the rhizome would also remain aerobic: it has a low resistance to diffusion (73 Ms m−3) and could receive sufficient oxygen by diffusion from the node. The data agree well with previous empirical measurements of convection in this species and show that diffusion and convection are both important processes for its aeration.
Productivity of leaves of a tropical tree, Theobroma cacao, grown under shading, in relation to leaf age and light conditions within the canopy
Authors: MIYAJI KEN‐ICHI , DA SILVA WALNY S. , ALVIM PAULO de T. 
Published: March 2003

summaryThe photosynthetic and respiratory activities of the leaves of a tropical tree, cacao, Theobroma cacao L., grown under shading, were determined in relation to leaf age and light conditions within the canopy, in order to gain a deeper insight into characteristics of the leaf population composing a canopy.The specific leaf weight and leaf water content varied with the height of leaves from the ground and/or the irradiance. The net photosynthetic rate also varied markedly depending on leaf age and irradiance. The leaves in full or nearly full irradiance (< 70% full daylight) attained the maximum rater. 60 d after the leaves emerged, and the rate decreased to nearly zero at a leaf age of c. 270 d.The nocturnal leaf respiratory activity was proportional to the photosynthetic activity during the day, but the proportional ratio was not constant throughout the survival period of leaves. Within the closed canopy, the upper leaves, which much higher ratios of respiratory to photosynthetic activity, under full or nearly full irradiance, tended to have much shorter mean longevities (c. 160 d) than the lower leaves under a lower irradiance (c. 310 d).
Effect of fertilization on ozone‐induced changes in the metabolism of birch (Betula pendula) leaves
Authors: LANDOLT W. , GÜNTHARDT‐GOERG M. S. , PFENNINGER I. , EINIG W. , HAMPP R. , MAURER S. , MATYSSEK R. 
Published: March 2003

summaryCloned cuttings of Betula pendula Roth were grown in field fumigation chambers at Birmensdorf throughout one growing season in filtered air with either < 3 (control) or 90/40 nl l−1O3(day/night; ozone generated from pure oxygen). Each ozone regime was split into high and low soil nutrient regimes by watering plants with either a 0.05 % or a 0.005% solution of a fertilizer which contained macronutrients and micronutrients.Fertilization had a strong effect on plant growth, enzyme activities and the expression of ozone‐induced effects at the biochemical level. The activities of PEPC and Rubisco were enhanced about threefold in the plants with high fertilization (HF). Significant effects of ozone were in most cases found only in the older leaves of the plants with low fertilization (LF), There, sucrose, glucose and fructose levels were enhanced. In both fertilization treatments, the number of starch granules along the minor veins was increased. These ozone effects point to a decreased or inhibited phloem loading. The increased PEPC activity and the enhanced malate levels in the ozone‐exposed plants might be the result of a redirection of carbon flow from sucrose synthesis and translocation towards anapleurotic processes, which can feed detoxification and repair of ozone injury as indicated by enhanced respiration. These findings agree well with the observed effects of ozone in lowering the root: shoot biomass ratio. Although there was a marked reduction in the O3/LF plants, O3/HF plants showed no significant response. Inositol was decreased under ozone exposure in both fertilizer treatments, contrasting with the pattern for carbohydrates.These results demonstrate the role of fertilization as an important modifier of ozone‐induced effects at the plant biochemical level. Well fertilized plants appear to cope better with the impact of ozone on metabolism.
Within‐plant relationships among wounding, jasmonic acid, and nicotine implications for defence in Nicotiana sylvestris
Authors: OHNMEISS THOMAS E. , McCLOUD ERIC S. , LYNDS GLADYS Y. , BALDWIN IAN T. 
Published: March 2003

summaryIn Nicotiana sylvestris Spegazzini and Comes (Solanaceae), we examined the relationships among wounding, endogenous leaf jasmonic acid (JA) pools, and whole‐plain (WP) nicotine accumulation over a range of wounding intensities and spatial distributions, in order to explore optimal defence (OD) theory predictions. We quantitatively wounded one or four leaves and then quantified: (1) JA in damaged and undamaged leaves 90 min after wounding; (2) WP nicotine concentration after 5 d (the times when JA and nicotine attain the largest wound‐induced concentrations). We find: (1) statistically significant, positive relationships on a leaf‐by‐leaf basis among the number of leaf punctures, endogenous leaf JA, and WP nicotine accumulation; (2) that young, undamaged leaves have a higher concentration of JA than do older, undamaged leaves, and produce a greater amount of JA per puncture than older leaves, but that all leaves have the same JA content (ng JA per leaf); and (3) that a damaged leaf produces less JA when other leaves in the canopy are wounded than when it is the onh wounded leaf in the canopy, but that when it is the only wounded leaf, the phylotactically adjacent, undamaged leaves do not increase their JA concentrations. The observation that younger leaves produce more JA per puncture than do older leaves is consistent with OD theory predictions. The observation that a small amount of damage localized to a single leaf is as effective as a larger amount of damage dispersed across the canopy in increasing leaf JA and WP nicotine accumulation shows the plant's ability to differentiate between dispersed and localized damage. Because the quantity of JA in a wounded leaf 90 min after wounding is a reliable indicator of the WP nicotine response to wounding, this trait provides insight into how plants integrate information about environmental insults and tailor their defence responses.
The effect of u.v.‐B radiation on u.v.‐absorbing secondary metabolites in birch seedlings grown under simulated forest soil conditions
Authors: LAVOLA ANU , JULKUNEN‐TIITTO RIITTA , APHALO PEDRO , DE LA ROSA TANIA , LEHTO TARJA 
Published: March 2003

summaryBirch (Betula pendula Roth) seedlings were grown under enhanced u.v.‐B radiation and simulated forest‐soil conditions, after which individual secondary metabolites were determined in the leaves. It was found that not all of the u.v.‐absorbing secondary metabolites of the seedlings responded to supplementary u.v.‐B radiation. Under increased u.v.‐B radiation, significant increases in concentration were observed only for the major flavonoid, quercitrin, the minor fiavonoid, myricetin‐3‐galactoside, and for chlorogenic acid. On the other hand, 3,4′dihydroxypropiophenone‐3‐β‐D‐glucopyranoside decreased under u.v.‐B irradiation. The concentration of phenolic compounds in the leaves changed during the growing season (between two harvests) but this change was not related to u.v.‐B enhancement. A low availability of mineral nutrients did not impair the capacity of the seedlings to accumulate u.v.‐protecting phenolic compounds under increased u.v.‐B radiation. The growth conditions used might have affected the intracellular concentrations of secondary metabolites, and thus furnished the birch seedlings with an increased tolerance of u.v.‐B radiation. These findings point to the significance of certain phenolic components in the protection of deciduous trees against u.v.‐B radiation.
Effects of nitrogen and water limitation and elevated atmospheric CO2on ectomycorrhiza of longleaf pine
Authors: RUNION G. B. , MITCHELL R. J. , ROGERS H. H. , PRIOR S. A. , COUNTS T. K. 
Published: March 2003

summaryLongleaf pine (Pinus palustrisMill.) seedlings were exposed to two concentrations of atmospheric CO2(365 or 720 μmol mol−1) and two levels of N (0.02 or 0.20 mg N g−1soil yr−1) within open‐top chambers for 20 months. Seedlings were adequately watered for 19 wk to ensure seedling establishment, after which two water‐stress treatments (target values −0·5 or −1·5 MPa xylem pressure potential) were implemented. Fine‐root samples were collected in July and November 1993, and in March and November 1994. Ectomycorrhizal and non‐mycorrhizal short roots per unit length of fine root were quantified. The percentage of ectomycorrhizal short roots and numbers of ectomycorrhizas per unit root length were higher for seedlings grown with elevated CO2, low N and adequate water. Interactions among main treatment variables demonstrated higher percentages of ectomycorrhizal short roots, fine root length per seedling, and total numbers of ectomycorrhizas per seedling for plants grown with high CO2(compared with ambient) or adequate water (compared with water stress) only under high N conditions. Increased fine‐root length and ectomycorrhizal colonization under elevated CO2resulted in higher (almost double) numbers of ectomycorrhizas per seedling at each sampling.
Effects of synthetic plant growth retardants and abscisic acid on root functions of Brassica rapa plants exposed to low root‐zone temperature
Authors: BIGOT JACQUES , BOUCAUD JEAN 
Published: March 2003

Possible interactions of two synthetic plant‐growth retardants during the short‐term response of Brassica rapa L. ssp. oleifera (DC.) Metzger plants to low root‐zone temperature were investigated by pretreating with mefluidide or paclobutrazol. Water and solute transfers were studied by measuring xylem sap volume flow (under root pressure exudation) and ion flow from the roots. Relations with nitrate uptake rate were also considered. Root pretreatment with paclobutrazol strongly restricted the cold‐inducible processes which normally restore water and solute flow from the root xylem. Paclobutrazol decreased the rates of nitrate uptake and exudation flow from the root xylem (principally by reducing root hydraulic conductivity) with dramatic consequences for ion flow, especially that of nitrate.The effects of root ABA pretreatment on plant response to root cooling were then studied separately or in association with a pretreatment with paclobutrazol. Despite a slight decrease in nitrate uptake rate, ABA pretreatment of the roots enabled the plant to develop rapid mechanisms for adaptation to cold constraint at the root level. Moreover, this action of exogenous ABA greatly reduced the effect of a simultaneous paclobutrazol pretreatment and partly restored water and solute flows.Thus, the improvement of plant resistance to cold conditions brought about by treatments with mefluidide and paclobutrazol (previously shown in long‐term experiments) cannot simply be explained by their short‐term effects.
Short‐term polyamine response in TMV‐inoculated hypersensitive and susceptible tobacco plants
Authors: RABITI A. L. , BETTI L. , BORTOLOTTI C. , MARINI F. , CANOVA A. , BAGNI N. , TORRIGIANI P. 
Published: March 2003

The short‐term polyamine response to inoculation, with tobacco mosaic virus (TMV), of TMV‐inoculated NN (hypersensitive) and nn (susceptible) plants of Nicotiana tabacum (L.) cv. Samsun was investigated. Free and conjugated polyamine concentrations, putrescine biosynthesis, evaluated through arginine decarboxylase (ADC) and ornithine decarboxylase (ODC) activities, and putrescine oxidation, via diamine oxidase (DAO) activity, were analysed during the first 24 h from inoculation. Results were compared with those of mock‐inoculated control plants. In NN TMV‐inoculated plants undergoing the hypersensitive response (HR), free putrescine and spermidine concentrations had increased after 5 h compared with controls; polyamine conjugates also tended to increase compared with controls. In both virus‐ and mock‐inoculated plants, ADC and ODC activities generally increased whereas DAO activity, which was present in controls, was detectable only in traces in inoculated tissues.In TMV‐infected susceptible plants, free putrescine and spermidine concentrations were lower at 5 h relative to controls, as were polyamine conjugates. No differences were revealed in ADC and ODC activities whereas DAO activity was not detectable. These results further support the hypothesis that polyamines are involved in the response of tobacco to TMV and that, only a few hours after inoculation, the response of hypersensitive plants is distinct from that of susceptible ones.
Host and cell type affect the mode of degradation by Meripilus giganteus
Authors: SCHWARZE F. W. M. R. , FINK S. 
Published: March 2003

Wood degradation by the white‐rot basidiomycete Meripilus giganteus (Pers.: Pers.) Karst. was studied in naturally infected and artificially inoculated wood of beech (Fagus sylvatica L.) and large‐leaved lime (Tilia platyphyllos Scop.). Semi‐thin sections revealed that the secondary walls of most fibres contained internal cavities. Three distinct types of cavity formation, which differed not only between hosts, but also between cell type and location in the annual ring, were identified.Within discoloured wood of naturally infected beech, the structure of the cavities and their formation by the associated hyphae were reminiscent of a soft‐rot. By contrast, cavity formation in artificially inoculated beech and large‐leaved lime wood differed from a soft‐rot mode of attack as extensive delignification always preceded cavity formation, and neither T‐branching, L‐bending, nor hyphal growth were found within cell walls. The formation of half‐moon shaped cavities in beech wood was present only in tension‐wood fibres. From large diameter hyphae, growing within the fibre lumen, numerous fine perforation hyphae extended transversely via helical cracks into the cell wall. Subsequent degradation of cellulose within concentric layers of the tension‐wood fibres commenced from the apices of perforation hyphae.Sections stained with ruthenium red and hydroxlamine‐ferric chloride, revealed that M. giganteus preferentially degrades pectin‐rich regions of the middle lamellae in xylary ray cells. In large‐leaved lime, such regions were uniformly located in the middle lamellae of axial and ray parenchyma. In beech wood, degradation of pectin‐rich middle lamellae regions commenced after the delignification of secondary walls and resulted in a conspicuous hollowing of multiseriate xylem rays. Plasticity in wood degradation modes by M. giganteus in large‐leaved lime and beech wood reflects variations in cell wall structure and/or prevailing wood conditions.