bluuebunny/crossref_metadata_2025_split huggingface dataset:
Induction of protoplast formation in the ectomycorrhizal fungus Paxillus involutus by the root rot pathogen Fusarium oxysporum
Authors: FARQUHAR M. L. , PETERSON R. L. 
Published: April 2006

SUMMARYCo‐culture of the pathogenic fungus Fusarium oxysporum f. sp. pini Schlecht. emend Snyd. & Hans, with the ectomycorrhizal fungus Paxillus involutus Fr. on potato dextrose agar caused no visible morphological changes in the fungi. Co‐culture on modified Melin Norkrans medium in petri plates yielded, however, protoplast formation at or near tips of P. involutus hyphae. No changes were visible in F. oxysporum as a result of co‐culture and the two fungi grew in close association with each other without inhibition. Staining with Calcofluor White M2R New and fluorescein diacetate displayed that, at this stage in development, a wall surrounding the protoplast was absent but a plasma membrane sheathed by an extracellular mucilage was present. Protoplasts lacking definite form adhered closely to adjoining hyphae while those with the characteristic spherical form were easily dislodged from hyphae. Average size of spherical protoplasts was 17–20 μm. Breaks were present in the hyphal wall in regions adjacent to protoplast formation and these may have been pathways for cytoplasmic leakage. Transmission electron microscopy revealed these breaks more clearly, and provided additional evidence of a plasma membrane around protoplast cytoplasm. Protoplasts contained few organelles except vesicles, larger electron dense bodies and occasional nuclei. Hyphae forming protoplasts often lacked cytoplasmic integrity although those not forming protoplasts appeared healthy.
Infectivity of pine and eucalypt isolates of Pisolithus tinctorius (Pers.) Coker & Couch on roots of Eucalyptus urophylla S. T. Blake in vitro
Authors: LEI J. , LAPEYRIE F. , MALAJCZUK N. , DEXHEIMER J. 
Published: April 2006

SUMMARYAn ultrastructural comparison of early stages of mycorrhiza formation on Eucalyptus urophylla was carried out using two isolates of P. tinctorius, one cultured from a sporocarp collected under pine and the other cultured from a sporocarp collected under eucalypt. Major differences at the fungus–root interface were observed 2 and 4 d following inoculation. Eucalypt root cells in contact with the isolate from pine developed a thickened cell wall, whereas the isolate from eucalypt was associated with an accumulation of extracellular fibrils. The fibrils stained positively for carbohydrates and protein. They were absent with the isolate from pine. Four days after inoculation with the isolate from eucalypt, acid phosphatase activity was detected along the fungal plasmalemma at the interface with host cells. This enzyme activity was not detected with the isolate from pine. Vacuolar acid phosphatase activity was detected in both fungal isolates when in contact with Eucalyptus roots. It is suggested that host recognition of ectomycorrhizal symbionts can be manifested within hours of inoculation with the fungal partner.
Proteinase activity in mycorrhizal fungi
Authors: LEAKE J. R. , READ D. J. 
Published: April 2006

SUMMARYThe ericoid mycorrhizal endophyte, Hymenoscyphus ericae (Read) Korf & Kernan, was grown in liquid media containing either ammonium, the amino acid alanine, peptide (di‐, tri‐, tetra‐ or hexa‐alanine), or bovine serum albumin (BSA) as sole nitrogen (N) source. The effects of the various N sources upon production of extracellular acid proteinase, its specific activity and growth of the fungus were determined.While extracellular acid proteinase was induced in the presence of each N source, enzyme production was considerably enhanced in the culture grown with BSA. Total enzyme activity in the culture solutions declined in the order BSA ≫ ammonium > peptides and alanine. Enzyme activity per mg dry weight of mycelium was greatest in the presence of BSA.Similar yields of fungal mycelium and rates of growth were observed regardless of N source.The results are discussed in relation to quantitative aspects of the N status of heathland soils.
Size classes of root diameter and mycorrhizal fungal colonization in two temperate grassland communities
Authors: REINHARDT D. R. , MILLER R. M. 
Published: April 2006

SUMMARYThis study addresses the hypothesis that the amount of fibrous roots (i.e., roots > 1.0 mm diameter) colonized by vesicular‐arbuscular mycorrhizal (VAM) fungi in grasslands is dependent upon root morphology. Two grassland communities with contrasting root system morphologies, a restored tallgrass prairie and an ungrazed pasture, were studied over a growing season. Although there was no difference in fibrous root biomass between the two communities, fibrous roots accounted for 99 % of the total root biomass in the pasture; but only 70 % of the total root biomass in the prairie. The length of fibrous roots was greater (P < 0.0001) in the pasture than in the prairie. Correspondingly, the mean diameter of roots in the pasture was 018 mm, but that in the prairie averaged 0.23 mm. Although the total length of fibrous roots colonized by mycorrhizal fungi did not differ between the two communities (P > 0.34), when the colonized lengths of roots within each of three size classes were compared, significant differences between the two communities were found. The ratio of the fraction of the root length colonized within a given diameter size class to the fraction of the total length of root with cortex occurring within that size class was used to compare the degree of association between roots and mycorrhizal colonization among the three diameter size classes. Changes in this ratio, termed the colonization index (CI), indicate that as the diameter size class of roots in a community increases, a greater proportion of the cortical root length within that size class is colonized by mycorrhizal fungi. Furthermore, despite community differences in the cortical and colonized root lengths within each diameter size class, the CI value for each root size class did not differ between communities. These findings suggest that in grasslands the degree of colonization by mycorrhizal fungi is more dependent upon the diameter size class distribution of the fibrous root systems than upon the species composition of the community.
Cell differentiation and mycorrhizal infection in Dactylorhiza majalis (Rchb. f.) Hunt & Summerh. (Orchidaceae) during germination in vitro
Authors: RASMUSSEN HANNE N. 
Published: April 2006

SUMMARYSeeds of Dactylorhiza majalis (Rchb. f.) Hunt & Summerhayes were sown in vitro with a compatible fungus. A mycorrhiza was established after infection through the rhizoids of the germinating seedling. Infection through the suspensor did occur, but these hyphae did not form pelotons, and embryo cells in contact with the hyphae were filled with a tannin‐like substance.Germination, and establishment of mycorrhiza, took about 14 days in vitro. From day 9 the protein reserves were hydrolysed, the protein vacuoles coalesced and starch accumulated in plastids. Certain epidermal cells developed nuclei about eight times original volume and produced rhizoids which emerged from day 11. After infection the hyphae formed pelotons in central cells with enlarged nuclei (16–64 times original volume). The intracellular hyphae developed close contacts with the hypertrophied host nuclei. Collapsed pelotons could be observed in cells from day 12, one day after infection. Meristematic activity in the uninfected chalazal end of the seedling began on day 12. On day 28 the first vascular tissue started to develop and on day 35 the beginning of a leafy shoot could be detected.
Variation in within‐morph incompatibility inhibition sites in heteromorphic Primula L.
Authors: WEDDERBURN FRANCES , RICHARDS A. J. 
Published: April 2006

SUMMARYThe inhibition sites for within‐morph incompatibility are reported for 52 species of Primula. Pollen tube inhibition usually occurs at more than one site; when only one site is involved, this is at the stigma surface. Inhibition sites usually vary between pins and thrums within a species, and inhibition characteristics vary widely between species, although related species are frequently similar. There is a close relationship between illegitimate seed set and failure of illegitimate tube inhibition.Total within‐morph incompatibility is only observed in two species, but for almost all species some compatibility is found in both morphs. Inhibition at the stigma surface results in more efficient incompatibility than inhibition within the stigma and style, although multiple‐site inhibition is the most efficient. Within‐thrum inhibition tends to occur more frequently at the stigma surface than does within‐pin inhibition.Four main classes of inhibition characteristics are noted. Some sections show inhibition site complexity in pins, but in others it has developed in thrums. Species with complex within‐morph inhibition in both pins and thrums occur in several unrelated taxonomic groupings.
The name of the pea: a quantitative history of legume classification
Authors: CRONK Q. C. B. 
Published: April 2006

SUMMARYDuring the period from 1753 to 1964, the balance between splitting and lumping (the median genus size) has remained unchanged in five classifications of the Leguminosae (Linnaeus, Persoon, Bentham, Taubert and Hutchinson), which span the period at approximately 50‐year intervals. This is in contrast with the situation in the Gramineae where increased splitting in recent classifications has resulted in smaller median genus size. However, generic sizes in the Leguminosae do not cluster around the median but are uneven: the frequency distribution of genus size in all the classifications is very skew, with many monotypic genera and some exceptionally large genera. This parameter, equality, changes considerably over time with a trend to more inequality of generic size. This is interpreted as a psychohistorical artefact of the classification process with newly discovered species tending to accrete to existing genera which act as‘nuclei’for‘chaining’. The few species which are too anomalous to fit into the large and diverse genera may be placed in monotypic genera, thus producing a pattern of many very small genera and few very big genera. The one exception to this trend is the classification of Bentham which is considerably more even than expected.The three subfamilies of the Leguminosae show similar overall trends to the family as a whole but exhibit consistent differences between each other in median genus size and equality of genus size. The Caesalpinoideae has even genus sizes and a low median genus size whereas the Mimosoideae shows the opposite, effects too marked to be explained entirely as psychohistorical artefact. These differences may be explained partly as artefact and partly in terms of differing evolutionary history if (1) the Caesalpinoideae is an ancient group primarily of relict species which have undergone little recent speciation, (2) the Mimosoideae are an ancient group which has undergone a massive bloom of recent speciation and (3) the Papilionoideae are a comparatively recently evolved group.
The palynological record of the King's Pool, Stafford, England
Authors: BARTLEY D. D. , MORGAN A. V. 
Published: April 2006

SUMMARYThe King's Pool is an elongated depression in which up to 21 m of organic sediments have been found. Details of the sediments and the macro fossils are given. The pollen diagram is presented in both percentage and concentration forms, and these show considerable differences especially for the Late Devensian period. The sequence begins at about 13 000 years BP though the pollen diagram begins near the end of the Windermere interstadial. It appears that there are a number of hiatuses in the sequence, the most important spanning most of the Atlantic period (Godwin pollen zone Vila). Forest clearance is evident from early in the Neolithic period with further clearance in the Bronze Age (shown most clearly in the concentration diagram) but with the greatest clearance at the beginning of the Iron Age. This latter clearance is accompanied by increased productivity of the lake, indicated by organic remains, including abundant blue‐green algae, suggesting eutrophication. Arable agriculture including cultivation of cereals and Cannabis seems to have increased near the end of the Roman period.
Fungal decomposition of attached angiosperm twigs I. Decay community development in ash, beech and oak
Authors: GRIFFITH G. S. , BODDY LYNNE 
Published: April 2006

SUMMARYInitial stages in the development of fungal decay communities were followed in attached ash (Fraxinus excelsior L.) twigs which had been stressed by girdling and defoliation, and in cut lengths from living twigs of ash, oak (Quercus robur L.) and beech (Fagus sylvatica L.) incubated under controlled drying regimes in the laboratory.Community development in artificially stressed ash twigs was similar to that predicted from previous direct observations. There was direct evidence that most primary colonizers in ash, including Phomopsis platanoidis Died, and Fusarium lateritium Nees., were present as endophytes in the bark of healthy twigs and subsequently colonized wood from this inoculum source. By contrast, secondary invaders were non‐endophytic fungi, including Peniophora lycii (Pers.) v. Hohn & Litsch and Libertella fraxinea Oganova. Secondary invaders began to colonize twigs after about 11 months; this was associated with a detectable reduction in moisture content.In healthy ash twigs there was evidence of superficial colonization of woody tissues, lying close to the bark, by endophytes which were not commonly isolated from dead ash twigs, including Aureobasidium pullulans (De Bary) Arnaud and Phoma macrostoma Mont. Superficial colonization was seasonal, reaching a maximum during the winter.A range of endophytes was isolated from healthy oak and beech bark, including Phomopsis spp., Cryptosporiopsis spp., Daldinia sp. and Xylaria spp. Some, but not all, of these endophytes were also isolated from the wood of dead attached oak and beech twigs, and some were able to colonize dying twig lengths under laboratory conditions. Whilst, Daldinia sp. and Xylaria spp. developed in dying twigs of all three tree species in the laboratory, neither were found in decaying twigs in the field. This may reflect different rates of drying in the laboratory and field.
Nitrogen metabolism in the ectomycorrhizal fungus Laccaria bicolor (R. Mre.) Orton
Authors: AHMAD IFTIKHAR , CARLETON TERRY J. , MALLOCH DAVID W. , HELLEBUST JOHAN A. 
Published: April 2006

SUMMARYBlended colonies of the ectomycorrhizal fungus, Laccaria bicolor (R. Mre.) Orton, grew axenically as a suspension of fine hyphae in a defined buffered medium with glucose (doubling time 1–2 d) but not acetate as the carbon source, and either ammonium or nitrate as nitrogen sources. A number of amino acids were found to be excellent nitrogen sources for this basidiomycete, but were less effective as sources of carbon. During post‐exponential growth in medium containing inorganic nitrogen, the fungal symbiont released amino acids. L. bicolor has the enzymatic potential to assimilate ammonium by the activities of glutamine synthetase, NADH‐glutamate dehydrogenase and NADPH‐glutamate dehydrogenase. It also contains highly active aspartate and alanine aminotransferases. The activities of glutamine synthetase, NADPH‐glutamate dehydrogenase and aspartate aminotransferase were greater in the presence of nitrate than in the presence of ammonium and declined as the culture aged, suggesting a biosynthetic role for these enzymes. In contrast, the activities of NADH‐glutamate dehydrogenase and alanine aminotransferase increased during post‐exponential growth, and also in cultures growing on amino acids as a carbon source, suggesting a catabolic role for these enzymes.
Root growth of Fagus sylvatica: impact of air quality and drought at a site in southern Britain
Authors: TAYLOR GAIL , DAVIES W. J. 
Published: April 2006

SUMMARYTransplants of beech, Fagus sylvatica, L. were planted in 1 m plastic tubes containing a mixture of peat and grit and sunk into the ground inside open‐top chambers at a site in southern Britain. Chambers were ventilated with either charcoal‐filtered or unfiltered air and water was withheld from half of the trees within each chamber. The influence of air quality on the growth and development of roots and interactions between air quality and drought were investigated. During May and June 1988 the growth of fine (diameter < 1.5 mm) and large roots (diameter > 1.5 m) was not significantly altered by air quality. A destructive harvest conducted in July revealed that trees exposed to ambient pollution had significantly longer roots (P < 0.05) compared with trees grown in filtered air, despite slightly less root dry weight (not statistically significant). Specific root length (SRL, root length per unit root dry weight) was also significantly larger (P < 0.05) for trees grown in the unfiltered chambers and exposed to pollution, suggesting a root system which was not only longer but also consisted of thinner roots, compared with the roots of trees grown in clean air. The effects of pollution were more pronounced for roots in the lower half of the 1 m profile.During August 1988, water was withheld from half of the trees within each chamber. Well‐watered trees exposed to unfiltered air had significantly less root dry weight (P < 0.05) compared with well‐watered trees grown in filtered air, although root length and SRL were both greater for trees grown in unfiltered air compared with those grown in filtered air. Again the effects were more pronounced lower in the root profile. Withholding water resulted in less root length being produced irrespective of air quality treatment, suggesting that trees exposed to pollution would not necessarily be more susceptible to drought‐stress. Root length was also measured non‐destructively in 1989 and again trees grown in unfiltered air had longer fine and large roots, compared with those grown in filtered air.These results illustrate the importance of measuring root length to complement estimates of dry weight, which may not be the best indicator of root function. The production of longer, thinner roots may be an important mechanism to compensate for reduced carbon allocation to, and dry matter accumulation by roots of trees exposed to pollution.
Influence of pH and plant nutrient status on ion fluxes between tomato plants and simulated acid mists
Authors: FOSTER JEFFREY R. 
Published: April 2006

SUMMARYDiffusion along concentration gradients, ion exchange, active uptake, and physical damage are possible mechanisms causing fluxes of ions between plant tissues and acidified moisture on plant surfaces. The temporal patterns of ion fluxes during individual wetting events should vary in a predictable manner in relation to moisture pH, plant nutritional status, and the operational mechanism. Tomatoes (Lycopersicon esculentum Mill.) were grown hydroponically at relative nutrient addition rates (Ra) of 7, 12, and 15% per day. At similar growth stages, the plants were exposed to HCl‐acidified mists of pH 2–5, 4–0, or 5–6 for 4 h, or left unmisted as controls. Whole‐plant throughfall was analysed for pH and ion concentrations after 15, 30, 60, 120, and 240 min. Surface chemical contamination was minimized by pre‐rinsing with deionized water. Except for H+ during the first 15–30 min, all ions showed efflux for the duration of the mistings. Effluxes were low (< 150μequiv m−2 h−1), time‐invariant, and unrelated to Ra at mist pH of 4.0 and 5.6. At pH 2.5, effluxes of K+, Mg2+, NO3−, and PO43− increased over time, while Ca2+ efflux increased during the first hour, then remained constant. Maximum efflux (105 to 730 μequiv m−2 h−1) mostly occurred at pH 2.5 and Ra= 17 % d−1, increasing in the order NH4+= SO42− < NO3− < PO43− < Ca2+= Mg2+ < K+ < H+. These results suggested that although ion diffusion and ion exchange contributed to observed effluxes, an additional mechanism, temporally accumulating physical damage to cuticles and cell membranes below a threshold pH between 4˙0 and 2˙5, was involved. Foliar concentrations of K, Ca, and Mg did not differ significantly among treatments, but ion effluxes into pH 2–5 mists removed 1–13 % of the whole‐plant element contents, with the largest removal for Ca.
Salinity effects on the stomatal behaviour of grapevine
Authors: DOWNTON W. J. S. , LOVEYS B. R. , GRANT W. J. R. 
Published: April 2006

SUMMARYAn investigation of the time‐course of inhibition of photosynthesis in salt‐stressed grapevine (Vitis vinifera L.) leaves revealed two types of stomatal behaviour. Up to tissue concentrations of 165 mM chloride the inhibition was due to a uniform decrease in stomatal conductance, as indicated from autoradiograms of 14CO2 fixation and no change in the relationship of assimilation to calculated intercellular partial pressure of CO2 (A‐C1) compared with control plants. The occurrence of non‐stomatal inhibition of photosynthesis at higher levels of leaf chloride, suggested by a decline in the slope of the calculated (A‐C1) relationship, was associated with non‐uniform 14CO2uptake over the leaf surface similar to that previously observed for ABA‐treated and water‐stressed grapevine leaves where non‐stomatal inhibition of photosynthesis was shown to be an artifact arising from non‐uniform stomatal behaviour. These observations also provide an explanation for the stimulation of photorespiration during salt stress.