bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of forest soil acidification on ectomycorrhizal and vesicular—arbuscular mycorrhizal development
Authors: DANIELSON R. M. , VISSER S. 
Published: April 2006

SUMMARYSeedlings of Pinus contorta Dougl. and Phleum pratense L. were grown in the greenhouse in forest floor (F/H horizons) and mineral soil from a P. contorla stand which had been acidified (pH 1.6 5.2) with S° dust over a 5‐year period. Although S° dust was the primary treatment it was assumed that acidification accounted for the major effects on the plants and mycorrhizas. Pinus contorla failed to grow below pH 2.8 and ectomycorrhizas were absent below pH 3.3. Pheleum pratense ceased growth at pH 3.3 and no vesicular‐arbuscular (VA) mycorrhizas were formd below pH 4.0. There did not appear to be any relationship between the relative abundance of coarse and fine VA mycorrhizal endophytes and soil acidity. Cenococcum geophilum L. was a common ectomycorrhizal associate of pine seedlings grown in the F/H soil, and E‐strain fungi (Complexipes), Mycelium radicis atrovirens Melin, Tomentella sp. and Suillus sp. were all more common in the mineral soi than in the F/H soil. Piloderma bicolor (Peck) Julich was observed to occur in large, discrete patches in the undisturbed natural stand but did not form ectomycorrhizas in the greenhouse. Both P. pratense and P. contorla were capable of good growth in extremely acid soils in a non‐mycorrhizal state.
The role of proteins in the nitrogen nutrition of ectomycorrhizal plants
Authors: ABUZINADAH R. A. , READ D. J. 
Published: April 2006

SUMMARYSeedings of Betula pendula L. were grown aseptically in the non‐mycorrhizal condition and in association with the mycorrhizal Fungi Hebeloma crustuliniforme (Bull, ex St. Am.) Quél Amanita muscaria (L. ex Fr.) Hooker or Paxillus incolutus (Batsch) Fr. They were supplied with the amino‐acid l‐alanine, or with peptides of between 2 and 6 alanine units, as sole nitrogen (N) sources. The ability of the different categories of plants to use these N sources was measured in terms of dry weight yield and nitrogen content of roots and shoots.While non‐mycorrhizal plants were unable to use any of these compounds as N sources, mycorrhizal infection provided the plants with some access to all of the N sources. The fungi differed, however, in the extent to which they mobilized the nitrogen, H. crustuliniforme being generally a more effective symbiont than A. muscaria which was, in turn, more effective than P. involutus. The yields and N contents of infected plants were normally higher on the peptides than on the amino acid, and in the two most effective fungi, the highest yield and nitrogen content were obtained in the treatments containing the largest peptide units. The physiological and ecological significance of these observations is discussed with particular attention being given to the role of mycorrhizas in the nitrogen nutrition of plants in natural ecosystems.
New aspects on the acquisition of biotrophic status by a vesicular—arbuscular mycorrhizal fungus, Gigaspora margarita
Authors: BÉCARD G. , PICHÉ Y. 
Published: April 2006

SUMMARYAn in vitro system for culturing the vesicular arbuscular (VA) mycorrhizal fungus Gigaspora margarita Becker & Hall with Ri T‐DNA transformed roots of carrot has been used to investigate the progressive dependency of a VA mycorrhizal fungus on its host during mycorrhizal establishment. The growth of hyphae from germinating spores of G. margarita was measured under different combinations of the following treatments: in absence or presence of root, with or without mycorrhizal colonization, with or without spore removal. Two distinct mechanisms of hyphal growth stimulation have been identified. The first required the presence of the root hut remained spore dependent. The second is exclusively root dependent. It has been demonstrated that the second mechanism is triggered when arbuscules are forming, indicating they are necessary for establishment of biotrophy. It is proposed that roots contribute to fungal growth by an inductive action, in addition to providing nutrients.
Early stages in colonization of Allium porrwn (leek) roots by the vesicular—arbuscular mycorrhizal fungus, Glomus versiforme
Authors: GARRIOCK M. L. , PETERSON R. L. , ACKERLEY C. A. 
Published: April 2006

SUMMARYLeek (Allium porrum L. cv. Titan) roots wore colonized by the vesicular arbuscular (VA) mycorrhizal fungus Glomus versiforme (Daniels and Trappe) Berch. External hyphae were of varying sizes and had a single‐layered wall surrounding a vacuolate cytoplasm. Intra‐hyphal hyphae were frequent in the extraradical mycelium. Some external hyphae formed small branches which initiated simple appressoria over the outer tangential wall of epidermal cells. Appressoria were multinucleate and possessed many structures which we have interpreted to be bacterium‐like organclles (BLOs). Infection hyphae formed by appressoria penetrated the radial cell walls of epidermal cells and were surrounded by an electron dense substance and host cell wall. Epidermal and cortical cells reacted frequently by forming cell wall thickenings. Hyphae in the exodermis formed coils which were surrounded by host plasma membrane but not host cell wall, and had many nuclei and BLOs.
Soil disturbance reduces the infectivity of external hyphae of vesicular—arbuscular mycorrhizal fungi
Authors: JASPER D. A. , ABBOTT L. K. , ROBSON A. D. 
Published: April 2006

SUMMARYWe conducted two glasshouse experiments to determine the effect of soil disturbance on the infectivity of external hyphae of vesicular–arbuscular (VA) mycorrhizal fungi. A nylon mesh was used to exclude plant roots while allowing fungal hyphae to grow into soil contained by the mesh. Hyphae of VA mycorrhizal fungi that had been separated from the original host plant root were still able to colonize bioassay plants rapidly and extensively. However, disturbance of the soil inside the mesh, by mixing for 1 min, almost eliminated subsequent VA mycorrhiza formation in that soil. Damage to the soil hyphal network by soil disturbance may contribute to the losses in mycorrhizal infectivity that have been observed after mining and cultivation.
Hyphae of a vesicular—arbuscular mycorrhizal fungus maintain infectivity in dry soil, except when the soil is disturbed
Authors: JASPER D. A. , ABBOTT L. K. , ROBSON A. D. 
Published: April 2006

SUMMARYWe examined the hypothesis that hyphae of a VA mycorrhizal fungus in dry soil remain infective, but that the infectivity decreases if the soil is disturbed. We used split‐pots, and sealed cylinders of nylon mesh, to create volumes of dry soil which contained hyphae of Acaulospora laevis Gerd. and Trappe that were attached, outside the mesh, to roots of living plants of Acacia satigna. (Labill.) H. Wendl. After the soil was dried in situ, the hyphae were detached from the roots without soil disturbance, or the soil containing the hyphae was disturbed. The infectivity of the hyphae after these treatments was then compared with that of intact hyphae.External hyphae of A. laevis remained highly infective in soil in which the matric potential had reached −21 MPa. Hyphae detached from the original host plant roots were equally infective. However, disturbance of the dry soil containing the external hyphae severely reduced the infectivity of the hyphae. After fluorescent staining, fungal structures with fluorescing nuclei were readily visible both within, and attached to, roots of A. Saligna which had no fluorescing nuclei.
Interpreting long‐term exponential growth of plant populations in a 250000‐year pollen record from Valle di Castiglione (Roma)
Authors: MAGRI DONATELLA 
Published: April 2006

SUMMARYThe pollen concentration diagram of a long core drilled in the lacustrine sediments of Valle di Castiglione (Roma) indicates that the increase of different plant populations is often exponential. Increases of trees, shrubs, herbs, aquatic plants and pteridophytes have been examined; their doubling times vary from a few to many hundreds of years. The durations of exponential growth last up to 6000 years.The interpretation of this phenomenon takes into account the close relation between climate, soil and vegetation. Under climatic conditions suitable for the expansion of a given population, growth depends on soil fertility, which, in turn, increases as the population grows. The process may be self‐fertilizing, producing in the long run a sum of nutrients greater than their consumption. Competition does not seem decisive in determining patterns and times of increase of plant populations.
Respiration and microalgal growth: a review of the quantitative relationship between dark respiration and growth
Authors: J.GEIDER RICHARD , OSBORNE BRUCE A. 
Published: April 2006

SUMMARYBiomass‐specific, dark respiration rates of microalgae vary by almost two orders of magnitude from 0.01 to 0.6 d−1. In general, dark respiration rates increase with growth rates in both intraspecitic and interspecific comparisons, but the precise relationship between respiration and growth rate varies. Under optimal conditions, respiration rates are about 20‐30% of growth rates, but the ratio of respiration to growth increases under suboptimal conditions. The intercept of plots of respiration rate vs. growth rate varied from < 0.01 to 0.4 d1, and the slopes of these relationships varied from < 0.1 to 1.0. Minimum maintenance metabolic rates of about 0.01 d 1 have been estimated for some microalgae by extrapolation of the initial slope of the light curve for growth to a hypothetical negative growth rate in darkness. The dimensionless total energy cost of synthesis and maintenance for heterotrophie growth of microalgae using either endogenously or exogenously supplied carbohydrates is typically 0.4‐1.2 for growth with ammonia or urea as a nitrogen source and 0.7‐1.4 for growth with nitrate as the nitrogen source.
Development of lines of radish differing in resistance to O3 and SO2
Authors: GILLESPIE CHRIS T. , WINNER WILLIAM E. 
Published: April 2006

SUMMARYThe potential for developing intraspecific lines of radish (Raphanus sativus L. cv, Cherry Belle) based on their relative resistance to either O3 or SO2 was examined using growth‐analysis techniques. Plants were exposed to either 0–10μ 1−1 O3 or 0.50 μ 1 −1 SO2 for 4 h day−1, 3 days week−1, for 3 weeks. Resistant and sensitive individuals were then selected and divided into four groups: O3 resistant (O3R), O3 sensitive (O3S), SO2 resistant (SO2R), and SO2 sensitive (SO2S) Cross‐pollinations were made among plants within the selected groups and seed collected. F1 populations were raised from the resulting seed and exposed to the same exposure regime. Net photosynthesis and stomatal conductance were measured during the final two fumigations, and plants were harvested immediately following the final exposure, divided into component parts, dried and weighed.O3 and SO2 generally caused biomass reductions in all the F1 groups. O3 reduced below ground growth more than SO2 leading to greater reductions in root/shoot ratios. O3R plants were resistant to both pollutants, showing little biomass reduction particularly from O3. Root/shoot ratios of these plants were altered less by pollutant exposure than non‐selected radishes. Shoot growth of SO2R plants was greater in O3 or SO2 than non‐selected plants, but below ground growth was similar. Selection for plants sensitive to either pollutant was not apparent from growth analysis, as growth of the sensitive plants was generally the same as that of non‐selected plants. Gas exchange results indicated greater stomatal conductance in O3S plants in filtered air than either non‐selected or O3R plants, while O3S plants had lower conductance rates in the O3 treatment.
Physiology and yield of field‐grown Brassica oleracea L. exposed to acidic fog
Authors: TAKEMOTO B. K. , JOHNSON A. G. , PARADA C. R. , OLSZYK D. M. 
Published: April 2006

SUMMARYField‐grown Brassica oleracea L. ev. Emperor (broccoli) plants were exposed to a range of treatments with simulated acidic fog in open‐field plots to examine the effect of fog chemistry on yield and growth, and to determine whether alterations in yield or growth were related to the development of foliar injury and/or the inhibition of net photosynthesis. Simulated fogs (i.e. pH values of 1.76, 2.23, 2.72, 3.22 or 5.48) with a liquid water content of 0.20–0.25 g m−3 were applied twice weekly for 10 weeks. Applications of pH 1.76 fog caused significant yield reductions (37%) relative to pH 5.48. Leaf dry weight responses were more sensitive to fog chemistry than yield. Leaf dry weight was significantly inhibited by 53, 25 and 9% in the pH 1.76, 2.23, and 2.72 fog treatment groups, respectively.The depression of yield by fog of pH 1.76 was closely correlated with the development of foliar injury and the inhibition of net photosynthesis on a percentage basis. Plants exposed to pH 2.23 or 1.76 fog consistently displayed amounts of injury ranging from 5 to 7% or 20 to 31%, respectively, whereas plants exposed to pH 2.72 fog or higher exhibited less than 5% injury throughout the study. Whole‐study average rates of net photosynthesis were significantly depressed by pH 1.76 fog (30% lower). The inhibition of net photosynthesis was coincident with increases in both mesophyll and stomatal resistances to CO2, but the ratio of mesophyll to stomatal resistance was not significantly altered.These findings provide evidence that repeated exposures to highly acidic fog (pH 1.76 or 2.23) may cause significant reductions in marketable yield and/or growth of B. oleracea, but substantive adverse effects would not be expected from exposures to fog of lower acidic strength. Although the inhibition of net phososynthesis in B. oleracea by acidic fog was coincident with decreased yield, reduced rates of CO2 assimilation appear to be due to the development of foliar injury (i.e. reduced photosynthetically active leaf area per plant) rather than a specific alteration in mesophyll or stomatal resistance to CO2.
Translocation of lysine from the host Melicope simplex to the parasitic dwarf mistletoe Korthalsella lindsayi (Viscaceae)
Authors: COETZEE J. , FINERAN B. A. 
Published: April 2006

SUMMARY 3H‐lysine was administered to severed ends of host stems infected by the parasitic mistletoe Korthalsella lindsayi (D. Oliver) Engl. Autoradiography at the ultrastructural level revealed that the tracer is transported from host to parasite and that it accumulates in lipid bodies in the haustorial parenchyma. At the host/parasite interface phloem is generally absent and the number of direct xylem tracheary to tracheary contacts are limited. In the interface area no cytoplasmic continuity could be observed between host and parasite, but numerous plasmatubules were present. It is concluded that organic substances such as the amino acid lysine can be translocated apoplastically from the host to the parasite and that plasmatubules are probably implicated in this process.
Effects of ectomycorrhiza on host growth and carbon balance in a semi‐hydroponic cultivation system
Authors: NYLUND JAN‐ERIK , WALLANDER HÅKAN 
Published: April 2006

SUMMARYEctomycorrhizal and control Pinus sylvestris L. seedlings were grown under steady‐state nutritional conditions in a semi‐hydroponic system. Free access to balanced low concentrations of mineral nutrients did not inhibit mycorrhiza formation. The large variations in relative growth rate observed after inoculation with different fungi demonstrated that the mycobiont has a substantial influence over the proportion of host photosynthate allocated for maintaining the symbiosis. Analyses with 14C‐tracer demonstrated that photosynthesis was considerably enhanced in mycorrhizal seedlings, even though N and Mg concentrations were similar in mycorrhizal and uninoculated seedlings. Although translocation and respiration were highly variable, they were enhanced in some seedlings. Nutrition had no demonstrable effects on shoot or root carbohydrate content, but auxin (IBA and IAA) treatments increased the carbohydrate concentrations. Several auxin treatments also accelerated translocation and respiration, but their effects on photosynthesis were variable. The results contradict some of the basic tenets in Björkman's (1942) carbohydrate theory, while providing circumstantial evidence in favour of Slankis's (1973) hormone hypothesis.
Time‐course of N2‐fixation (15N) in the field by clover growing alone or in mixture with ryegrass to improve pasture productivity, and inoculated with vesicular—arbuscular mycorrhizal fungi
Authors: BAREA J. M. , AZCÓZ R. , AZCÓN‐AGUILAR C. 
Published: April 2006

SUMMARYThe isotope 15N was used to estimate N2‐fixation by white clover, and N‐transfer from clover to perennial ryegrass. Pure stands of each of these pasture plants and a mixed sward of both were established in a field soil in which it had been demonstrated that vesicular‐arbuscular mycorrhizal inoculation was necessary for suitable development of the clover. All plants, whether clover or ryegrass, received the same amount of a selected mycorrhizal inoculum. The 15N/14N ratio of the grass in pure stands was used to evaluate N2,‐fixation by clover growing alone, and that of the grass in the mixture to estimate that by the companion clover. Tentative evidence of N‐transfer was obtained by comparing the 15N/11N ratio in the grass growing alone with that when mixed with the legume.In spite of a decline with time in 15N enrichment, the N2‐fixation rates were about the same throughout the growing season and for the two cropping systems. The total N, P and dry matter yields in the grass/clover mixture were greater than in monocultures. A lower 15N enrichment of the grass growing mixed compared to that growing alone, suggesting N‐transfer, was only obtained at the second harvest. The mycorrhizal colonization of the grass in the mixed grass/closer sward was significantly enhanced, as compared with that of the grass in pure stands. Mycorrhizal hyphae are known to be involved in NH4+ uptake, translocation and transfer to the host plants, and this may partly explain the improvement of pasture productivity when grass and mycotropic legumes are grown together.
Effects of soil and plant phosphorus concentrations on vesicular‐arbuscular mycorrhiza in sorghum plants
Authors: De MIRANDA J. C. C. , HARRIS P. J. , WILD A. 
Published: April 2006

SUMMARYThe effect of soil and plant phosphorus (P) on mycorrhiza was studied using a split‐root technique. In this experiment, sorghum (Sorghum bicolor (L.) Moench.) plants inoculated with the vesicular‐arbuscular (VA) mycorrhizal fungus Glomus macrocarpum (Tul. & Tul.), were subjected simultaneously to low and high phosphate concentrations applied to a phosphorus deficient Brazilian Dark Red Latosol. Phosphorus was translocated from one half of the root system to the other. When small additions of P were made to the soil, mycorrhizal infection. spore numbers and external hyphae increased compared with the unsupplemented soil. Translocation of phosphorus into roots growing in unsupplemented soil had little effect on percentage root infection, spore number or external hyphae in that compartment although infected root length increased slightly. In the treatment where soil P and plant P were high, percentage root infection and external hyphal growth were both similarly reduced. In the high phosphate treatments although percentage root infection was reduced, the total length of mycorrhizal root was not affected by phosphate fertilization.
Root temperature affects mycorrhizal efficacy in Fraxinus pennsylvanica Marsh
Authors: BORGES RITA G. , CHANEY WILLIAM R. 
Published: April 2006

SUMMARYGrowth parameters and carbohydrate contents were determined for Fraxinus pennsylvanica Marsh, seedlings inoculated with Glomus macrocarpum Tul. and Tul. or Glomus fasciculatum (Thaxt.) Gerd. and Trappe, and for uninoculated controls that were grown in a greenhouse for 16 weeks at root temperatures of 15, 25 or 35 °C. Seedling growth responded rapidly to mycorrhizal inoculation when root temperatures were 25 or 35 °C. Response to inoculation at 15 °C was delayed but seedlings at this temperature finally attained the size of those grown at 25 and 35 °C. Growth of noninoculated plants was best at 15 and 25 °C. Inoculation with mycorrhizal fungi moderated the adverse effect of higher root temperature. Infection of roots by both fungal species was greater at 25 °C than at 15 or 35 °C. Sugar content increased as root temperature increased whereas starch content was inversely related. Both soluble sugar and starch content were less in mycorrhizal than in nonmycorrhizal seedlings.
Mycorrhiza development in onion in response to inoculation with chitindecomposing actinomycetes
Authors: AMES ROBERT N. 
Published: April 2006

SUMMARYTwelve actinomycetes, originally isolated from spores of Glomus macrocarpum Tul. & Tul., were inoculated into nonsterilized soil containing G. macrocarpum and G. mosseae (Nicol. & Gerd.) Gerd. & Trappe. The chitin‐decomposing actinomycetes were strongly antagonistic toward fungi, bacteria or actinomycetes, or combinations of these based on prior studies. Eight Streptomyces, two Nocardia, and two unidentified species were tested for their effects on mycorrhiza development in onion (Allium cepa L.), plant growth and nutrient content, soil hyphal density, and soil populations of bacteria and actinomycetes. None of the actinomycetes adversely affected plant growth or nutrient content. The lower foliar P content of two of the treatments could be explained as a dilution effect brought about by the significantly larger shoot growth. With few exceptions, the soil microbial populations and saprophytic fungal hyphal densities were not significantly different from the controls. Seven of the twelve actinomycetes significantly increased the percent mycorrhizal root colonization and four significantly increased the density of hyphae > 5μm in diameter, predominantly those of vesicular‐arbuscular mycorrhizal (VAM) fungi. This is the first study to demonstrate that actinomycetes isolated from spores of a VAM fungus can be beneficial to mycorrhiza development and growth of onion in a nonsterile soil system.
Interaction of soil bacteria, mycorrhizal fungi and orchid seed in relation to germination of Australian orchids
Authors: WILKINSON K. G. , DIXON K. W. , SIVASITHAMPARAM K. 
Published: April 2006

SUMMARYEndotrophic bacteria were isolated from the mycorrhizal tissues of 12 out of 13 tested species of Western Australian terrestrial orchids. The bacteria were placed into eight groups based on u.v. light fluorescence, Gram staining and colony characteristics. The most commonly isolated bacteria from 9 out of the 12 orchid species sampled were strains within the Pseudomonas fluorescens‐putida group. The abundance of bacteria followed a seasonal pattern that differed between orchid genera especially on the basis of the morphology of fungus infected tissue. There was little evidence of specificity of bacterial groups to orchid taxa or part of the plant infected by the fungus. Symbiotic germination of Pterostylis vittata seed in association with seven bacterial isolates showed a significant promotion of germination and seedling development with three bacterial strains. The influence of a fourth strain was no different to the control while the remaining three strains significantly suppressed seedling development.