bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of indigenous arbuscular mycorrhizal endophytes on the development of six wild plants colonizing a semi‐arid area in south‐east Spain
Authors: ROLDAN‐FAJARDO B. E. 
Published: April 2006

SUMMARYThe effect of arbuscular mycorrhizal fungi (AMF) an six plant species that frequently grow in areas of Mediterranean climate in south‐east Spain was studied. In semi‐arid soils, the most abundant AMF was Glomus aggregation Schenck and Smith, followed by Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe. The vascular plant species studied were Dittrichia viscosa (L.) W. Greuter (Asteraceae); Dactylis glomerata L., Piptatherum miliaceum (L.) Cosson, and Slipa tenacissima L. (Poaceae); Retama sphaerocarpa (L.) Boiss., and Ulex parviflorus Pourret (Fabaceae). Legumes were studied with single and dual symbiosis (Rhizobium and AMF). In a greenhouse experiment, inoculated plants developed better than noninoculared controls, as shown by dry weight and tissue N and P content. Plants inoculated with G. aggregation grew better than plants inoculated with G. mosseae. For this reason G. aggregatum was chosen for a field experiment, in which this AM fungus increased shoot dry mass, shoot length, and percent survival after transplantation. The effects of soil microorganisms on development, survival and fertility of native plants, their influence on the effects of the erosion, and their importance in plant repopulation programmes are discussed.
The role of the extracellular sheath in recognition and attachment of conidia of Discula umbrinella (Berk. & Br.) Morelet to the host surface
Authors: VIRET OLIVIER , TOTI LUIGI , CHAPELA IGNACIO H. , PETRINI ORLANDO 
Published: April 2006

SUMMARYThe role of the conidial sheath in the recognition process and in the attachment of conidia of the beech endophyte, Discula umbrinella, to the host surface was investigated. After treatment of conidia with different lectins the adhesion of conidia to the host surface was effectively inhibited. A strong fluorescence was observed after treatment of conidia with TRITC‐labelled concanavalin A. Fluorescence with TRITC‐labelled wheat germ agglutinin was observed only on spores subjected to enzymatic digestion with proteases. Observations with the transmission electron microscope (TEM), after labelling sections with colloidal gold conjugated lectins, confirmed the presence of mannose and/or glucose in the extracellular sheath. Chitin was present in the conidial ceil wall but not in the extracellular sheath. Enzymatic treatment of the conidial sheath resulted in strongly reduced attachment and changes in the binding of fluorescence‐labelled lectins. TEM studies of partially digested conidia revealed that snail enzyme modified only slightly the structure of the sheath, while proteases completely dissolved the fibrillar sheath leaving a comparatively smooth cell wall with no fibrillar structures on its surface. We conclude that a proteinaceous sheath is responsible for the adhesion of Discula umbrinella conidia to the host and that glycoproteins are involved in the recognition and attachment process. This attachment mechanism closely parallels the only other recognition system studied biochemically in endophytes, and is similar to the few analogous cases studied in plant‐pathogenic fungi, pointing to the functional relatedness of endophytic and pathogenic interactions.
Atypical, green leaf blotch lesions on barley leaves infected by Rhynchosporium secalis (Oud.) Davis
Authors: DAVIS HELENA , FITT B. D. L. , EVANS R. L. 
Published: April 2006

SUMMARYAtypical, green leaf blotch lesions were observed on senescent leaves in winter barley crops and sometimes developed on barley leaves inoculated with conidia of Rhynchosporium secalis in a glasshouse. Similar atypical lesions were induced on barley leaves inoculated with conidia of R. secalis and then grown in controlled environments at 10 °C and 80% rh. Microscopic examination of green lesions from these three sources showed that hyphae of R. secalis had colonized the subsidiary cells of stomata so that guard cells were swollen, resulting in enlarged stomatal pores. Additionally, spore initials had erupted through the leaf cuticle of some leaves. Most spore initials did not develop into mature conidia when leaves were incubated for 24 h at 20 C in a closed chamber at l00% rh, but aerial hyphae grew out from the leaf surface. Thus, atypical green lesions produced a much smaller number of spores than typical leaf blotch lesions.
An epidemiological study of Puccinia punctiformis (Str.) Röhl as a stepping‐stone to the biological control of Cirsium arvense (L.) Scop.
Authors: FRANTZEN J. 
Published: April 2006

SUMMARYThe infection cycle of the autoecious rust fungus Puccinia punctiformis on the clonal plant Cirsium arvense was described in terms of intensity (amount of pathogen per unit area and used for systemic infection) and extent (area occupied by the pathogen and used for local lesion infection) at four grassland sites in The Netherlands. The incidence of systemic infection was relatively low and systemically infected shoots were typically concentrated at a few locations within a site. Incidence of local lesion infection was relatively high and widespread in ail sites. Spatial and temporal distribution of teliospores, the inoculum for systemic infection, were quantified in order to explain the relatively low and spatially unequal incidence of systemic infection. Because of the large impact of systemic infection on C. arvense shoots, it is concluded that a spatially homogeneous distribution of teliospores may be a prerequisite for the biological control of C. arvense by P. punctiformis.
Chitinase and peroxidase activities are induced in eucalyptus roots according to aggressiveness of Australian ectomycorrhizal strains ofPisolithussp.
Authors: ALBRECHT C. , BURGESS T. , DELL B. , LAPEYRIE F. 
Published: April 2006

SUMMARYPeroxidase and chitinase activities were measured in roots ofEucalyptus globulussppbicostataKirkp. during colonization byPisolithussp. isolated from underEucalyptus.Ten fungal isolates, ranging from poor to good root colonizers, were selected to represent a range of ectomycorrhizal aggressivity. The induction of chitinases and peroxidases was strongly related to the aggressiveness of the fungal strain. Only good colonizers, that is strains which rapidly form differentiated ectomycorrhizas, induced a strong response in the plant. Therefore, it can be concluded that these enzymes are not responsible for poor root colonization by the less aggressive strains. The chitinase response ofEucalyptusroots to contact with fungal extracts differed only slightly between weakly and strongly aggressive strains. This suggests that a major component of differential induction observedin vivois the consequence of root colonization, tissue penetration and the ability to deliver elicitors to the plain print to and during rant colonization
Spatial distribution of mycelia of the liana (L‐) biotype of the agaric Crinipellis perniciosa (Stahel) Singer in tropical forest
Authors: GRIFFITH G. W. , HEDGER J. N. 
Published: April 2006

SUMMARYA detailed investigation of the Liana biotype (L‐biotype) of Crinipellis perniciosa (Stahel) Sing, was conducted in Ecuador. Basidiocarps of the L‐biotype were consistently found in association with stems or debris of the liana Arrabidaea verrucosa (Standl) A. Gentry, although no symptoms associated with witches’broom disease, were observed. Debris colonized by the L‐biotype were often connected via pseudosclerotial pads to living sterns of A. verrucosa. Pairings between 87 isolates obtained from basidiocarp stipe tissues or liana bark cores from three sites permitted 37 somatic compatibility groupings (SCGs) to be defined. In all cases these were found to be very restricted in geographical distribution, a situation which contrasts markedly with the distribution of SCGs in the pathogenic and non‐outercrossing eocoa biotype. Mating pairings between single basidiospore isolates confirmed chat the outercrossing mechanism of the L‐biotype is muitialletic and that no significant biological barriers to gene flow exist between coastal and Amazonian populations. Several lines of evidence suggested that mycelia belonging to the same SCG (= genet) were isogenic. Correlations between field observations and the distributions of both SCGs and mating type factors art‐ discussed in relation to patterns of dispersal, establishment and spread of this fungus.
Elevated CO2, water relations and biophysics of leaf extension in four chalk grassland herbs
Authors: FERRIS RACHEL , TAYLOR GAIL 
Published: April 2006

SUMMARYDiurnal measurements of leaf or leaflet, extension, water relations and cell wall extensibility (ø) were made on young growing leaves of four chalk downland herbs (Sanguisorba minor Scop., Lotus corniculatus L., Anthyllis vulneraria L. and Plantago media L.) growing in controlled environment cabinets and exposed to either ambient or elevated CO2. This study revealed differences in that effect of CO2 and the‐ control of leaf growth between the four species. Leaf extension rate (LER) increased significantly at night (average over 8 h) in elevated C02 for S. minor A. vulneraria and P. Media with a significant increase over the first 4h of darkness for S. minor, L, corniculatus and P. media, whilst for S. minor and P. media average day‐time LER (over 16 h) also increased significantly in elevated CO2, as compared with ambient CO2. Water potential (ψpS), solute potential (ψpS), turgor pressure (P), yield turgor (Y) and the effective turgor for growth (Pe) were measured using psychrometers. Bollrte potentials of s, minor, A. vulneraria and P. media decreased significantly following exposure to elevated co2 with a Significant reduction in ψpS, during the day in A. Vulneraria. Turgor pressure increased significantly in elevated CO2 as compared with ambient CO2 in A. vulneraria but there was no effect of elevated CO2 on P in the uther species. effects of CO2 on ψpS; or ψpS; were observed, Leaf cell wall extensibility (ø) increased significantly in leaves of V. minor, L. corniculatus and P. exposed to elevated Co2. whereas in A. vulneraria, there was no effect of CO2 on extensibility.These results suggest that the mechanism by which elevated CO2 promotes leaf growth differs between species arisce in S. minor, L. corniculatus, and p media. CO2 through an influence on cell wall properties, whist in A vulneraria higher values of P explain that increased leaf growth in elevated CO2 for this species.
Accumulation of ABA in maize roots in response to root severing
Authors: ZHANG JIANHUA 
Published: April 2006

SUMMARYWhen isolated maize (Zea mays L.) routs were incubated tW 3 h in o fully hydrated state in air, ABA content was found to increase by around 100% in nil the different root tissues examined ‐ i.e. mature primary root sections. young and growing primary root sections, secondary roots and primary root tips ‐ from both well watered plants and previously droughted plants. This ABA increase was not turgor‐related, as usually is the case in draughted plants, and was not quantitatively related to the injury in the cutting surface. A time‐ sequence of ABA accumulation showed a peak accumulation at about 2–3 h after initial incubation. Oxygen was essential for this increase in ABA accumulation because‐ when roots were incubated in pure nitrogen, no such increase was found. Evidence suggests that this increase was derived from xanthophylls. the common precursors for stress‐induced ABA.Maize leaves did not show such an accumulation when incubated under the same conditions. When halt the root system was severed, ABA content in the remaining half root system increased by Kill 100–200% in 3 h. We suggest that there is a systemic effect on the ABA biosynthesis in the root system following the shock of root severing, and that roots may supply substantial amounts of ABA to the shoots even at time when there is not apparent dehydration.
The epidermal surface of the maize root tip
Authors: ABEYSEKERA R. M. , MCCULLY M.E. 
Published: April 2006

SUMMARYThe surface of the young epidermal cells of maize roots is composed o) three layers; the inner layer (LI), which is the outer epidermal Wall, overlaid by a pellicle consisting of a thick, coherent inner layer (L2) and a very thin, loosely organized outer layer (L3). The entire surface can be removed intact to produce either narrow, circumferential strips or apical halftones, by gently prying it loose in the circumferential direction by hand with insect pins. Usually only short remnants of anticlinical walls of the epidermal cells remain attached. These isolated surface pieces always curl outward at the free circumferential edges in the longitudinal direction of the original intact root. When the strips are deliberated stretched alone their long axis (i.e., the original circumferential direction) they elongate irreversibly by us much us two thirds of their length, before showing some elastic deformation and breaking. Some plastic deformation may occur in the original longitudinal direction of the root during removal of the strips. The plastic deformation opens the helicoidal array of microfibrils in the L1 layer. Deformation also produces structural changes over the original radial walls and those transverse anticlinal walls that form boundaries of cell packets derived from single cells. In these positions the L1 layers over adjacent cells separate in the direction of the applied stress. This occurs by the separation of the L I layers of adjacent cells and the stretching of the inward projection of the amorphous L2 layer of the pellicle which lies; over these original anticlinal walls. There is much less or no separation of the L1 layers over anticlinal walls Of adjoining daughter cells in the epidermis.The pellicle always remains firmly attached to the outer epidermal wall during removal of the surface strips. On removal, these strips shorten in their original longitudinal direction in situ, indicating a release of tension imposed by underlying cells. Their outward curling suggests stress between the wall and pellicle of the outer epidermal surface in the intact root.These findings focus attention on structural differences between sites where anticlinal walls of different origin join the outer surface, and on possible differences in surface extensibility at each sites.
Seasonal changes in water use of ash trees exposed to ozone episodes
Authors: WILTSHIRE J.J.J. , UNSWORTH M. H. , WRIGHT C. J. 
Published: April 2006

SUMMARYYoung ash trees (Fraxinus excelsior L.) growing in the field were exposed to episodes of 150 nl 1‐1 ozone, or to clean air, in open‐top chambers at the University of Nottingham, Sucton Bonington Campus, UK, in the summer of 1992. The episodes were for 8 h daily and for 1‐4 in succession, with a seasonal total of 27 d. From late‐June until mid‐September 1942, flow of water in the stems of individual trees was measured using a heat balance method. Short‐term effects of ozone exposure on stem flow were not detected. However, in the longer‐term, daily integrated stem flow values for the ozone treatment decreased throughout the measurement period relative to the clear air treatment. Further data analysis showed that integrated stem flow values for morning, evening and for the more stable central part of the day changed in a similar way, but this was statistically significant only for the evening period. No treatment differences, however, were detected in night‐time water use values.This response was probably mediated by changes in stomatal resistance and, if applicable to other species, has important implications for the long‐term growth of trees in regions where photochemical ozone is common.
Late Epipalaeolithic wood remains from el‐Wad Cave, Mount Carmel, Israel
Authors: LEV‐YADUN SIMCHA , WEINSTEIN‐EVRON MINA 
Published: April 2006

SUMMARYThirty‐two Early Natufian (13‐11 k years BP) pieces of charcoal were found in the recent excavations of el‐Wad Cave, Mount Carmel, Israel. These includedTamarixsp. (10 pieces),Quercus calliprinosWebb (10),Quercus ithaburensisDecne. (three),Quercussp. (two),Salixsp., probablyacmophyllaBoiss, (four),Cupressus sempervirensL. (one), andMyrtus communisL. (one), and an unidentified dicotyledonous plant. These finds indicate that the Natufians used various local woody plants in their economy, in a Mediterranean climate similar to that of the present, during the closing stages of the Pleistocene.
Rates of diffusion into roots of maize
Authors: CANNY M.J. , HUANG C.X. 
Published: April 2006

SUMMARYThe rate at which solutes may move in the cell wall apoplast of roots was assessed by measuring the diffusivity (D) of a dye, sulphorhodamine G (SR), in freshroots of field‐grown maize. Pieces of axile and branch roots from regions with soil sheaths (with immature late metaxylem) and without sheaths (with mature late metaxylem) were placed in SR solution for 5, 20 and 80 min, removed, rinesed and freeze‐substituted. The water‐soluble SR was retained in position in the tissues during anhydrous embedding and sectioning. The distance of radial penetration of the dye was measured from micrographs taken in the fluorescence microscope. Fick's aecond law was used to calculate values of D. The values are expressed relative to the value of D in water (Daq). Mature axile roots uniformly gave values of D=Duq/1000. In immature axile roots D varied from 0 (no penetration through the hypodermal walls) through Duq/1000 to D aq/40 (the maximum value found). This variation probably arises from a developmental sequence. with D high in the region to 10 cm from the tip. zero in the region 10‐25 cm from the tip, and low further back (merging with values for mature roots). In branches of both immature and mature roots also, D was highly variable, from zero to Daq/40. SR was found to penetrate through the endodermis of axes and branches, following sub‐microscopic paths around the lining of pits in the secondary walls. It is concluded that soil solutes probably enter roots at the outermost layer of cells, and that the cell wall apoplast is most unlikely to be a path for flowing water.
Salt stress‐induced changes in superoxide dismutase isozymes in leaves and mesophyll protoplasts from Vigna unguiculata (L.) Walp.
Authors: HERNÁNDEZ JOSE A. , DEL RÍO LUIS A. , SEVILLA FRANCISCA 
Published: April 2006

SUMMARYThe effect of salt stress (NaCl and/or KCl) on the specific activity of superoxide dismutase (SOD) isozymes in leaves from cowpea plants and in mesophyll protoplasts from cowpea leaves was examined. In leaves, mitochondrial Mn‐SOD was significantly decreased by 35 mM (up to 35%) and 100 mM NaCl (up to 60%), whereas, under the same conditions, cytosolic and mitochondrial Cu, Zn‐SOD I was slightly diminished and chloroplastic Cu, Zn‐SOD II did not show a response. In protoplasts, the specific activity of SOD isozymes was decreased as a function of both the salt concentration and the type of salt used Mn‐SOD was again the most salt‐sensitive isozyme, but in contrast to whole leaf preparations. Cu, Zn‐SOD II in protoplasts was markedly inhibited by NaCl and Cu, Zn‐SOD I showed an intermediate sensitivity. KCl concentrations equivalent to those of NaCl were less effective in inhibiting the SOD isozymes, suggesting the existence of specificity for certain ions. In protoplasts salt inhibition of SODs was reversible. However, Mn2+ was necessary for total recovery of Mn‐SOD activity in NaCl‐treated protoplasts. The in vitro results suggested a competitive inhibition of SOD isozymes by salts. A possible competitive inhibition of SOD activity in salt‐treated cowpea plants was also suggested. Finally, the possible correlation between plant response to NaCl and the potential of SOD isozymes was analyzed.
Canopy photosynthesis of CO2‐enriched lettuce (Lactuca sativa L.). Response to short‐term changes in CO2, temperature and oxides of nitrogen
Authors: CAPORN S. J. M. , HAND D. W. , MANSFIELD T. A. , WELLBURN A. R. 
Published: April 2006

SUMMARYThe canopy net photosynthesis (Pn) of lettuce (Lactuca sativa L. ev.‘Ambassador’) was analyzed under controlled conditions simulating the winter glasshouse atmosphere. Prior to measurements the plants were grown in CO2‐enriched air of 1000 μmol mol−1, at a photosynthetic photon flux density (PPFD) of 280 μmol m2 s−1 (400–700 nm) and a day/night air temperature of 16/13 °C.Short‐term changes in CO2 concentration significantly changed the initial gradient of the photosynthetic response to incident PPFD. Maximum photosynthetic efficiency of the crop increased from 0·041 mol CO2 mol photons−1 (equivalent to 8·2 μg CO2 J−1 and 9·4% on an energy basis) at 350 μmol mol−1 to 0·055 mol CO2 photons−1 (10·9 μg CO2 J−1 and 12·7% on an energy basis) at 1000 μmol mol−1. Transfer from low to high CO2 also lowered the light compensation point, but did not affect dark respiration. The large response of Pn to transient changes in CO2 indicated that the lettuce canopy did not acclimate to growth in 1000 μmol CO2 mol−1, in contrast with the effect of growth in high CO2on Pn in single mature leaves reported earlier.A reduction in air temperature from 16 to 6 °C at a concentration of 1000 μmol CO2 mol−1 halved the rate of dark respiration and reduced the light compensation point, but had no direct effect on the maximum efficiency with which the crop utilized light. Subsequently at low light (below 200 μmol m−1 s−1) Pn was greater at 6 than 16 °C. Between a PPFD of 250 and 300 μmol m−2 s−1 canopy Pn was similar at all temperatures.Addition of 2·0 μmol mol−1 nitric oxide to an atmosphere of 1000 μmol CO2 mol−1 caused a rapid and reversible reduction of canopy Pn, which was greater at the lowest temperatures. The average inhibition was 6·6 at 16 °C and 28·8% at 6 °C; this was not explained by differences in the rate of pollutant uptake, which was less in the cooler conditions.The results are discussed in relation to development of optimal growing conditions for production of glasshouse lettuce at low light and low temperature during winter in the UK.
Time course of oxidant stress biomarkers in flag leaves of wheat exposed to ozone and drought stress
Authors: FANGMEIER A. , BRUNSCHÖN S. , JÄGER H.‐J. 
Published: April 2006

SUMMARYProtein content, catalase activity (CAT), non‐specific peroxidase activity (POD), ascorbic acid content (AsA) and malondialdehyde content (MDA) were estimated in flag leaves of spring wheat exposed to ozone and drought stress in open‐top chambers. Four harvests were carried out at different developmental stages to estimate the time course of these parameters. Senescence was enhanced by ozone which was reflected in the time course of the oxidant stress biomarkers. Protein content decreased, and POD and MDA increased only after the leaves had experienced high doses of ozone, whereas AsA levels were raised in ozone‐treated plants after only a short exposure period. CAT did not significantly respond to ozone treatment, but, ozone accelerated the progress of its time course. Drought stress did not influence the time course of any of the estimated parameters, but led to somewhat increased levels of AsA.