bluuebunny/crossref_metadata_2025_split huggingface dataset:
Infection structures of fungal plant pathogens – a cytological and physiological evaluation
Authors: MENDGEN KURT , DEISING HOLGER 
Published: April 2006

SUMMARYMany fungi differentiate specific infection structures in order to infect the host plant. The spore attaches to the host surface, the cuticle, and the germ tube may recognize suitable penetration sites, over which an appressorium is formed. Additional wall layers in appressoria of many fungi suggest that this structure supports increasing pressure during the penetration process. During appressorium formation, synthesis of polymer‐degrading enzymes is often initiated. Cutinases, cellulases and pectin‐degrading enzymes can be formed in a developmentally controlled or adaptive, i.e. substrate‐dependent, fashion. The penetration hypha develops below the appressorium. This hypha has a new wall structure and exhibits features which serve to breach the plant cell wall. However, at present it is not clear whether penetration hyphae arising from appressoria are more efficient in penetration or induce less damage than hyphae which penetrate without detectable special adaptations. The infection hypha differentiates within the host. During differentiation a characteristic set of enzymes is synthesized to enable successful establishment of the host‐pathogen relationship. If, as in most cases, multiple forms of cell wall‐degrading enzymes are formed by the pathogen, mutagenesis or deletion of a gene encoding one of these enzymes very often has no effect on pathogenicity or even virulence. Proof is missing very often that an enzyme is needed at the right time and at the right site of infection.Events occurring during differentiation of fungal infection structures are reviewed with special emphasis onMagnaporthe grisea, Colletotrichumspp., and rust fungi, and common features which may be of importance to the success of infection are discussed.CONTENTSSummary193I.Introduction193II.Spore and germ tube195III.The appressorium199IV.The penetration hypha201V.The infection hypha204VI.Future prospects208Acknowledgements208References208
Scutellospora calospora (Nicol. & Gerd.) Walker & Sanders associated with subterranean clover: dynamics of colonization, sporulation and soluble carbohydrates
Authors: PEARSON J. N. , SCHWEIGER P. 
Published: April 2006

SUMMARYTwo time‐course experiments were conducted to investigate the relationship between colonization and sporulation by Scutellospora calospora (Nicol. & Gerd.) Walker & Sanders colonizing roots of subterranean clover (Trifolium subterraneum L.).The percentage of root length colonized by S. calospora increased up to 49 d in expt 1 and 32 d in expt 2 after which it declined. At this stage, there was no further increase in mycorrhizal root length but a sharp increase in non‐mycorrhizal root length. In expt 1, the soluble carbohydrate concentration of the roots decreased during the first 49 d, followed by a sudden increase, coinciding with the decline in the percentage of root length colonized. One week before this the shoot P inflow also decreased. In both experiments, sporulation by S. calospora occurred after the decline in colonization.During sporulation there is no further spread in colonization within the root, which may result in increases in soluble carbohydrate concentration within the root. Spore formation may be aided by carbon stores located in the external auxiliary bodies formed by species of the genus Scutellospora.
Acquisition of nitrogen by external hyphae of arbuscular mycorrhizal fungi associated withZea maysL.
Authors: FREY BEAT , SCHÜEPP HANNES 
Published: April 2006

SUMMARYThe objective of this study was to examine the ability of arbuscular mycorrhizal (AM) fungi to take up nitrogen from soil and transport it to the host plant. Maize (Zea maysL.) associated withGlomus intraradicesSchenck and Smith or left uninoculated was grown in containers which were divided by a nylon net into a root compartment and a hyphal compartment. A 40 μm pore size nylon net was used to exclude plant roots while allowing fungal hyphae to grow into soil confined by the net.15N tracer was supplied either as inorganic N or as organic N to the hyphal compartment at a distance of 5 cm from the net.Inoculation with the AM fungus increased the15N content of maize compared to the non‐mycorrhizal controls when N was applied as (15NH4)2SO4. However, there was no conclusive evidence that AM hyphae could derive N from organic15N sources. Most of the increased N uptake of mycorrhizal plants occurred by hyphal translocation from the hyphal compartment to the root compartment. Higher N uptake by mycorrhizal plants with access to the hyphal compartment was indicated by depletion of total15N in the soil of that compartment. Cutting the extraradical hyphae in the hyphal compartment in order to sever their connection with the host roots decreased the15N uptake of the maize plants. A time‐course study with inorganic15N over 26 d showed thatG. intraradicestransported most of the15N between 10 and 15 d after15N application, whereas the non‐mycorrhizal control plants had a consistently low concentration of15N throughout the period of sampling.Nitrogen transport by external hyphae of three AM fungi,G. intraradices, Acaulospora laevisGerdemann and Trappe andGigaspora margaritaBecker and Hall associated with maize, was further investigated. The results indicated that different isolates of AM fungi differ in the efficiency of hyphal N transport as a consequence of the different patterns of hyphal spread in the soil or of the different capacity for uptake by unit length of hyphae.
Nitrogen translocation between Alnus glutinosa (L.) Gaertn. seedlings inoculated with Frankia sp. and Pinus contorta Doug, ex Loud seedlings connected by a common ectomycorrhizal mycelium
Authors: ARNEBRANT KRISTINA , EK HANS , FINLAY ROGER D. , SÖDERSTRÖM BENGT 
Published: April 2006

SUMMARYUptake and translocation of nitrogen was studied in laboratory microcosms consisting of Alnus glutinosa (L.) Gaertn., Frankia sp., Paxillus involutus (Fr.) Fr. and Pinus contorta Dougl. ex Loud. P. involutus was shown to form a fully functional ectomycorrhizal association with alder as well as pine, and the seedlings thus became interconnected by a common mycelium.When microcosms were exposed to 15N2 gas, interplant translocation of 15N was observed in two out of three experiments. 15N2 was fixed by Frankia and translocated to all other parts of the system. In the two experiments in which interplant translocation occurred, between 5 and 15% of the 15N recovered was found in the pine seedlings.Within seven days, fixed N2 was incorporated into amino acids in the Frankia nodules, translocated to both the A. glutinosa and P. contorta seedlings and incorporated into macromolecules. In alder seedlings, citrulline and ornithine were the free amino acids that had both the highest 15N enrichment levels and concentrations. In pine, glutamine and citrulline had the highest 15N concentrations, and glutamine had the highest level of 15N enrichment. 15N enrichment levels were greatest in the nodules, at between 5.5 and 29% in the different amino acids and 12% in the macromolecular fraction. Enrichment levels decreased with increasing distance from the nodules.The uptake and translocation of 15N applied as 15NH4Cl to the mycelium was also studied. 15N was incorporated into amino acids in the mycelium and translocated further in this form. Generally, free amino acids had high 15N enrichment levels in the mycelium, decreasing along the translocation pathway. Citrulline and glutamine were the amino acids with highest 15N concentrations in all parts of the system. 15N was also found in the macromolecular fraction.
Impaired nodule function in Medicago polymorpha L. infected with alfalfa mosaic virus
Authors: WROTH J. M. , DILWORTH M. J. , JONES R. A. C. 
Published: April 2006

SUMMARYThe effects of alfalfa mosaic virus (AMV) on growth, nodule formation and nodule function in the annual burr medic, Medicago polymorpha cv. Circle Valley, were investigated in glasshouse pot experiments. Systemically‐infected plants from AMV‐infected seed produced 21% less shoot dry weight and accumulated 24% less fixed nitrogen in shoots than healthy plants when harvested 53 d after germination. At day 75, infected plants showed similar shoot dry weight losses (22%), but the quantity of nitrogen fixed fell by only 15%. At day 53, soluble sugar, starch and bacteroid concentrations in nodules were unaffected by AMV infection, but nitrogenase specific activity was decreased by 25% and soluble amino acids by 20%.Although AMV infection resulted in no differences in the number of nodules formed in the first 11 d after germination or at any harvest thereafter, nodule mass was decreased by 23% for virus‐infected plants at day 53. However this difference disappeared by day 75. Growth of AMV‐infected plants was decreased probably because of impaired N2 fixation with nodule function affected rather than nodulation. Increased nodule mass relative to plant weight in virus‐infected plants, seen at day 75, implied some degree of compensation for the limitation in N2‐fixing capacity. ELISAs for AMV antigen indicated that nodules were active sites of virus multiplication.
Needle chlorosis in Sitka spruce following a three‐year exposure to low concentrations of ozone: changes in mineral content, pigmentation and ascorbic acid
Authors: LUCAS PETER W. , RANTANEN LEENA , MEHLHORN HORST 
Published: April 2006

SUMMARYTwo‐year‐old seedlings of Sitka spruce were exposed to 70 nl 1−1ozone or to filtered air over three successive summers in outdoor large‐scale fumigation chambers (Solardomes). Seven months after the last period of exposure to the pollutant and just prior to budburst, upper‐surface chlorisis affecting only the older needles of ozone‐exposed trees was observed. In many respects, the symptoms appeared to be similar to those characteristic of type 1 spruce damage occurring in parts of mainland Europe. Chlorophyll pigments were reduced in the ozone‐exposed older foliage, but no change in the ratio of chlorophylls to carotene was observed. The content of ascorbic acid was clearly related to the amount of foliar damage observed on the trees exposed to ozone and the largest increases were seen in those trees which were most visibly damaged. Although none of the foliage examined was deficient in any of the nutrient cations which were measured, the concentration of Mg in the older needles was significantly reduced by exposure to ozone, irrespective of damage symptoms. Exposure to ozone also resulted in increases in the ratios of K: Mg and Ca: Mg. In the older needles, leaching of Mg2−and K−by 0.5 mM H2SO4, pH 3.0, was enhanced by prior exposure to ozone, but the amounts removed were small (< 6%). It is suggested that long‐term exposure to ozone has a cumulative effect on plant tissue and that the observed chlorosis was the result of accelerated senescence.
Primary homostyly in Primula L. subgenus Sphondylia (Duby) Rupr. and the evolution of distyly in Primula
Authors: AL WADI HUSSEN , RICHARDS A. J. 
Published: April 2006

SUMMARYWe have studied eight species classified within Primula L. subgenus Sphondylia (Duby) Rupr. Two have monomorphic flowers and four have typically distylous flowers. P. floribunda Wall, includes both monomorphic and distylous races, while P. boveana Decres. has an incompletely discontinuous dimorphism for style length and pollen size, but is monomorphic for anther position. All the species have been tested and they are fully self‐fertile.Evidence suggests that dimorphisms for style length (G/g), pollen size (P/p) and anther position (A/a) are each under independent genetic control. In the monomorphic P. verticillata, variations in stigma papilla length and style cell length appear to result from developmental correlates with style‐length variation. Both the monomorphic species show some continuous variation for herkogamy.Several of the species studied show an incomplete development of the full distylous syndrome typical of most Primula species. If it is assumed that these represent evolutionary stages in the development of the full syndrome, and if it is assumed that diallelic incompatibility evolved after the evolution of distyly, then it would appear that the components of the distyly linkage group are likely to have evolved from a non‐herkogamous ancestor in the following order: (i) short style mutant G; (ii) small pollen mutant p; (iii) low anther position mutant a.
Effect of wounding on the relations between vascular rays and vessels in Melia azedarach L.
Authors: LEV‐YADUN SIMCHA , ALONI RONI 
Published: April 2006

SUMMARYThe axial and radial derivatives of the cambium showed contrasting wound responses in Melia azedarach L. The vascular rays became larger, less spaced, and their shapes were modified following wounding. As the wound effects vanished with time, ray size, spacing and shape returned to normal patterns. On the other hand, following wounding, vessels became smaller, and fibres were not formed. Vessels returned to normal size, and vessels and fibres reverted to their normal pattern when wound effects vanished. These changes in the patterns of vascular rays, vessels and fibres reflect the nature of the regulatory mechanisms of their formation: axial signal flows, and the involvement of wound effects.
Species‐dependent patterns of fructan synthesis by enzymes from excised leaves of oat, wheat, barley and timothy
Authors: CAIRNS ANDREW J. , ASHTON JENNIFER E. 
Published: April 2006

SUMMARYExcised leaves of oat, wheat, barley and timothy were illuminated continuously for 24 h and shown to accumulate both sucrose and fructan. The fructan complements of the four species were compared with the well‐characterized pattern from leaves of L. temulentum L. by thin‐layer chromatography (TLC). Wheat and barley had similar patterns of oligosaccharides, accumulating isokestose, kestose and a range of oligofructans up to an apparent degree of polymerization (DP) of 10. Oat leaves accumulated neokestose in addition to kestose and isokestose. The oligofructans of oat also extended up to DP 10, though the pattern was more complex than that of wheat and barley. Timothy leaves accumulated fructan predominantly of apparent DP ≤ 16 and little smaller oligofructan. Analysis of concentrated carbohydrate extracts showed isokestose, kestose and a ladder of oligofructans of apparent DP in the range 4 to ≤ 20 in induced timothy leaves. The results showed that leaves of each grass accumulated a distinct and species‐specific pattern of fructan.Concentrated enzyme preparations from illuminated leaves of each species were incubated at 30 °C with 400 mol m−3 sucrose at pH 4.6 in the presence of 16 mol m−3 pyridoxal hydrochloride. The preparations catalyzed the de novo net synthesis of trisaccharides and larger oligofructans at rates approximating to rates of soluble carbohydrate accumulation in the tissue. On TLC, the enzyme products exhibited a marked resemblance to the complement of native fructan in the source tissue. The data demonstrate that the species specificity of the fructan complement can be explained by the properties of synthetic enzyme(s) alone, and is not dependent upon structural features of intact cells or tissues.The established view of fructan synthesis holds that the polymerizing enzyme, fructan: fructan fructosyl transferase (FFT), is inhibited by sucrose. The enzymes from all five grass species manufactured fructans of DP ≤ 3 in the presence of high concentrations of sucrose (above 200 mol m−3). Hence the properties of these grass fructan polymerases differ from those of FFT.
Binding of monoclonal antibodies to vegetative tissue and fucose‐containing polysaccharides of Fucus serratus L.
Authors: GREEN JONATHAN R. , STAFFORD CHRISTOPHER J. , JONES J. LEIGHTON , WRIGHT PHILIP J. , CALLOW JAMES A. 
Published: April 2006

SUMMARYMonoclonal antibodies (MAbs FS1–FS12) have previously been used to study the organization of cell surface glycoproteins on sperm and eggs of the brown alga Fucus serratus L. These antibodies were raised against Fucus sperm, but three (FS2, FS4 and FS5) also bind to the egg cell surface, and one (FS9) binds internally to polyphenol bodies in the egg. Evidence from immunofluorescence studies with the MAbs, using confocal laser scanning microscopy, has shown that the glycoproteins on the surfaces of both sperm and eggs are organized into domains. In the present study, the full set of MAbs was tested for cross‐reaction with F. serratus vegetative tissue in order to make a comparison with the gamete cell surfaces and to see whether any of the MAbs localized to particular regions of the mature thallus. A new MAb, FS13, which was raised to Fucus egg antigens, has also been characterized and used in this study. The results of ELISA, dot blot assays and indirect immunofluorescence tests show that the four MAbs which cross react with eggs (FS2, FS4, FS5 and FS9) also bind to vegetative tissue. Three MAbs (FS1, FS7 and FS12) bind to sperm and vegetative tissue, and MAbs FS3, FS6, FS8, FS10 and FS11 bind specifically to sperm. FS13 binds to egg vesicles and to vegetative tissue, but not to sperm. Western blotting and inhibition assays using ELISA have shown that the antigens recognized by the MAbs in vegetative tissue are different from those recognized on gametes, and glycoproteins on the latter are specific to each cell type (i.e. sperm or egg). Only FS7 and FS12 of the cross‐reacting MAbs recognize glycoproteins in vegetative tissue. They bind to most cell types, as does FS9 which recognizes polyphenols. The MAbs FS2, FS4, FS5 and FS13 all recognize fucose‐containing polysaccharides in vegetative tissue; however they recognize different epitopes and localize to different regions of the thallus. It is possible to distinguish between the amorphous matrix in the medulla which is FS13+, the mucilage at the plant surface which is FS2/5+ and the mucilage plug in the ostiole which is FS4+ FS2/5+. In addition FS13 and FS2/5 also label the walls of cells in the medulla. The results are compared with previous findings on the localization of fucoidan and ascophyllan in Fucus tissue.
Interphase and preprophase microtubule organization in some polarized cell types of the liverwort Marchantia paleacea Bert.
Authors: APOSTOLAKOS P. , GALATIS B. 
Published: April 2006

SUMMARYThe organization of interphase and preprophase‐prophase microtubules was studied in photosynthetic filament mother cells (PFMCs), photosynthetic filament cells (PFCs), mucilage papilla mother cells (MPMCs) and mucilage papillae (MP) of Marchantia paleacea Bert. These cell types exhibit polarized growth resulting, (a) in the formation of cell outgrowths followed by asymmetrical division (PFMCs and MPMCs), or (b) in the development of a tubular cell shape (PFCs and MP). The above cell types display an interphase cortical microtubule ring perpendicular to the axis of growth. In PFMCs and MPMCs it resides at the base of the cell outgrowth, while in PFCs and MP it has a median location. This microtubule ring is involved in the deposition of transverse, circumferentially aligned, cellulose microfibrils, defines the site where cell protrusion formation occurs and affects cell morphogenesis. In differentiated MP microtubules are rearranged in longitudinal or oblique cortical arrays. PFCs and MP also contain a prominent system of endoplasmic microtubules which may be involved in cytoplasmic polarization. In PFMCs, PFCs and MPMCs the interphase microtubule ring seems to function as a preprophase microtubule band (PPB). In the asymmetrically dividing PFMCs and MPMCs the PPB is complete but in symmetrically dividing PFCs it may be interrupted. The cell plate meets the parent wall at sites adjacent to the PPB cortical zone. These observations reveal further peculiarities in cortical microtubule organization and particularly in the PPBs of M. paleacea. Possible factors underlying the formation of complete or interrupted PPBs are discussed.
Impact of O3 and SO2 on reproductive development in oilseed rape (Brassica napus L.). I. Pollen germination and pollen tube growth
Authors: BOSAC C. , BLACK V. J. , BLACK C. R. , ROBERTS J. A. , LOCKWOOD F. 
Published: April 2006

SUMMARYA single exposure of pollen of Brassica napus L. cvs Tapidor or Libravo to 100 nl l−1 ozone (O3) either in vitro or in vivo on the anthers of intact plants had no significant effect on either pollen germination or pollen tube growth. Exposure of dry pollen to 200 nl l−1 sulphur dioxide (SO2) also produced no significant effect. However, pollen germination was significantly reduced and pollen tube growth impaired in both cultivars when pollen was exposed in unbuffered incubation medium to 200 nl l−1 SO2. The pH of the unbuffered medium fell from 6.5 to 5.5 during fumigation, suggesting a role for acidification in the observed SO2‐induced effects. This view is supported by evidence that percentage germination decreased linearly with pH in culture media buffered to provide pH values ranging from 6.05 to 3.0. Pollen tube growth was also impaired at pHs of 5.6 and below. The significance of pollutant‐induced impairment of pollen germination and growth for reproductive development and the influence of moisture in modifying the impact of SO2 and O3 are discussed.
Effects of acid, or ammonium‐enriched, artificial mist on leaf blight of London plane [Platanus×acerifolia (Ait.) Willd.] and on the behaviour of the causal fungus, Apiognomonia veneta (Sacc. & Speg.) Höhn.
Authors: SURY ROMAN VON , FLÜCKIGER WALTER 
Published: April 2006

SUMMARYThree types of artificial mist (acid = A, pH 3.0, 1400 μequiv. total ionic strength l−1; NH4+‐enriched = N, pH 5.4, 1400 μequiv. l−1; and control = C, pH 4.9–5.1, 10–15 μequiv. l−1) were used to detect the effects of wet deposition on the fungus Apiognomonia veneta (Sacc. & Speg.) Höhn. and on the susceptibility of its host tree, the London plane [Platanus×acerifolia (Ait.) Willd.], to leaf blight or anthracnose. On a nutrient‐poor agar, germination of conidia of A. veneta was strongly inhibited by mist A. Germination in mists N and C was higher, being 22 and 25 %, respectively. In autumn and spring, London plane seedlings were sprayed 15 times with each of mists A, N or C. Thereafter, leaves were inoculated with conidia. At this time, the pH of all leaf surfaces was similar. Inoculation in spring led to typical leaf blight symptoms. However, infection was light and no significant differences in symptom development were detected between mist treatments. After the C pre‐treatment, the germination of conidia was significantly inhibited on leaf surfaces, and in leaf washings, when compared with the A and N pre‐treatments. More spores germinated in a water blank than in leachates from C‐misted trees. A fungistatic, phenolic compound was found in leachates and isolated by TLC. It is suggested that this compound was involved in the inhibitory effect of the leaves treated with a control mist, but was removed or inactivated by mist A and N. We conclude that constitutive resistance of London plane leaves is affected adversely by acid and/or nutrient‐enriched mist.
Effects of pH on arbuscular mycorrhiza I. Field observations on the long‐term liming experiments at Rothamsted and Woburn
Authors: WANG G. M. , STRIBLEY D. P. , TINKER P. B. , WALKER C. 
Published: April 2006

SUMMARYThe percentage colonization of roots by arbuscular mycorrhizal fungi was measured in the field in two crops of spring oats (Avena sativa L.) and one of maincrop potatoes (Solanum tuberosum L.), successively grown over a period of 3 yr on the long‐term liming experiments at Rothamsted and Woburn. In both crops, all years, both phosphorus treatments and at both sites, percentage colonization was little affected by soil pH from over a range approximately 4.5 to 7.5. There was little effect of pH on crop yields. Up to nine species of coarse endophyte could be identified from spores (≤ 50 μm diameter) in plots of pH 5.5 and above. There were markedly fewer spores at (approximately) pH 5.5 and none in the most acid plots.