bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hybridization between European and Asian dandelions (Taraxacum section Ruderalia and section Mongolica)
Authors: MORITA TATSUYOSHI , MENKEN STEPH B. J. , STERK ADRI A. 
Published: April 2006

SUMMARYIn order to investigate crossability between the European section Ruderalia Kirschner, H. Øllgaard & Štěpánek and the Asian section Mongolica Dahlst. of the genus Taraxacum Wigg., artificial hybridization experiments were carried out.After inter‐sectional crosses on the diploid level, Mongolica plants showed high fruit‐set, not strikingly different from either the control (within‐populational crosses) or inter‐specific crosses within the same section. However, a substantial decrease of fruit‐set was detected when Ruderalia plants were the seed parents.Electrophoretic analysis revealed that Ruderalia seed parents in inter‐sectional crosses showed relatively low out‐crossing rates with low fruit‐set, whereas Mongolica plants as seed parents showed high out‐crossing rates, mostly 100%. These results indicate that the crossing‐barrier is stronger in the direction from Mongolica to Ruderalia than vice versa.Crosses between diploid Mongolica (♀) and triploid Ruderalia (♂) were also successful, although fruit‐set was far lower than in 2x‐2x crosses, a result which confirms previous reports. Contrary to published accounts, it was found by means of electrophoretic analyses that some 87.5 % of the progeny in 2x‐3x crosses were not true hybrids but sexual diploids originating from self‐fertilization. Only approximately 12.5 % of the progeny were found to be true agamospermous triploid or tetraploid hybrids. A strong doubt is raised concerning reports in the literature which assume that diploid hybrids originate in 2x‐3x crosses. The possible reasons why self‐incompatibility was broken down by triploid pollen are discussed.
Chloroplast development and nuclear gene expression in cotyledons of soybean seedlings
Authors: SAITO G. Y. , CHANG Y. C. , WALLING L. L. , THOMSON W. W. 
Published: April 2006

SUMMARYWith the greening of soybean cotyledons after germination, development of the photosynthetic membrane system and particularly granal stacking were correlated with decreasing chlorophyll a/b ratios. Chlorophyll a/b binding proteins are known to be localized mainly in the appressed membrane regions and to have a role in mediating granal membrane appression. The chlorophyll a/b binding protein genes became operative very early in the development of the photosynthetic membrane system and coincided with incipient granal formation. However, the accumulation of chlorophyll a/b binding protein mRNAs decreased as the chloroplasts approached full development. As predicted from the literature, an early amyloplast developmental stage was observed, and prolamellar‐like structures appeared early in the development of the chloroplasts, but subsequently disappeared. The reported amoeboid stage that follows the amyloplast phase was not observed, and starch persisted until quite late in development of the chloroplasts. Also, deformations in the shape of the developing chloroplasts indicated that they were amoeboid as they increased in size and as granal formation increased. Phytoferritin accumulations were observed at every stage of development, suggesting that it was not utilized during chloroplast development.
Internal secretory structures in Hypericum (Clusiaceae): H. perforatum L. and H. balearicum L.
Authors: CURTIS J. D. , LERSTEN N. R. 
Published: April 2006

SUMMARY Hypericum species have translucent oil cavities; many species also have superficially similar black internal structures. Contradictory descriptions of both structures emerged from 19th century studies, which we review here. Our study of Hypericum perforation L. leaves and petals shows typical schizogenous translucent oil cavities that develop with a uniseriate epithelium. Black structures, in contrast, are nodules, each composed of several large cells lacking a central intercellular space and surrounded by a biseriate sheath of flattened cells. Nodule cells accumulate black, granular, but non‐resinous contents. The ‘streaks’ that traverse petals are elongate tubular cavities or nodules, except for some chimerical tubes composed partly of each. Hypericum balearicum L. leaves have bulging, pustular cavities. A large cellular nodule forms first, by non‐synchronous cell divisions within the leaf mesophyll, and is surrounded by a sheath of two to three flattened cell layers. The central cells then separate unevenly to form an irregular cavity into which isolated cells and clusters of cells intrude, some of which continue to divide as other cells degenerate. Little or no oil accumulates in the cavity, and the peripheral lining of cells is very irregular to flattened and empty. Both species studied exhibit secretory structures with previously undescribed anatomical features.
Metabolism of [15N]glycine and [13C]glycine by Dionaea muscipula studied by gas chromatography‐mass spectrometry
Authors: GREENAWAY W. , MAY J. , ENGLISH S. , WHATLEY F. R. 
Published: April 2006

SUMMARYPlants of Dionaea muscipula Ellis fed for 24 h via trap lobes with [13C]glycine or [15N]glycine metabolized the glycine in the fed trap lobes only. Both 13C and 15N labelling was detected in glycine and serine and l5N labelling in alanine, aspartic acid, glutamic acid and 4‐aminobutanoic acid extracted from fed trap lobes. Limited amounts of [4‐15N]aminobutanoic acid and serine were translocated to the lamina of the fed trap lobes but neither these, nor other labelled amino acids, were detected in other parts of the plant. No 13C labelling was detected in compounds other than glycine and serine.
Mcchanism of flood tolerance in reed, Phragmites australis (Cav.) Trin. ex Steudel
Authors: GRIES C. , KAPPEN L. , LÖSCH R. 
Published: April 2006

SUMMARYImportant factors, such as porosity, respirational O2 consumption, O2 release of the roots and iron oxidation on the root surface, which are involved in the flood tolerance of Phragmites australis were investigated in northern Germany. The porosity of the different organs was determined as 58% for rhizomes, 42% for culms and 23‐38% for adventitious roots. Mean respirational O2 consumption of below ground organs was measured at 5, 10, 15 and 20°C as respectively 0.25, 0.5, 0.8 and 1.75 nmol O2 g−1dry mass s−1. The saturation concentration was estimated to be less than 0.017 mmol O2 1−1up to 15°C and 0.03 mmol O2 1−1at 20°C. From values of the root O2 gas exchange obtained from entire plants predictions are made concerning the O2 status of the roots under field conditions throughout the year. The O2 release for a reed stand was calculated as 65‐129 mg O2 m−2h−1in summer conditions. The oxidation power of the roots was further demonstrated by the development of iron hydroxide‐plaques on the root surface.
Iǹfectivity of pine and eucalypt isolates of Pisolithus tinctorius on roots of Eucalyptus urophylla in vitro
Authors: MALAJCZUK N. , LAPEYRIE F. , GARBAYE J. 
Published: April 2006

SUMMARYTwo isolates of the ectomycorrhizal fungus Pisolithus tinctorius (Pers.) Coker and Couch were inoculated on to roots of Eucalyptus urophylla S. T. Blake in vitro and a comparison made of the rate of ectomycorrhizal development. Both isolates initiated ectomycorrhizal roots but the time of onset of root colonization and the rate of formation varied with the isolate. An isolate cultured from a sporocarp collected from under eucalypts in Australia rapidly colonized roots of E. urophylla and initiated mycorrhizas after 2 d incubation, whereas an isolate obtained from sporocarps collected from under pines in the United States developed ectomycorrhizas only after 7 d incubation. Dual inoculation of E. urophylla seedlings using a paper‐sandwich technique again showed the rapid colonization of roots by the eucalypt isolate even when roots were inoculated 7 d previously with the pine isolate. These in vitro observations support field observations that there are variable degrees of plant species ‐ fungal isolate compatibility, implying specificity, and this is an important factor influencing successful ectomycorrhiza formation and development.
Ectomyeorrhiza formation in Eucalyptus
Authors: DELL B. , MALAJCZUK N. , THOMSON G. T. 
Published: April 2006

SUMMARYThe structure of mature tubercles collected from a Eucalyptus pilularis forest in Queensland, Australia, is described. The smooth, pale yellow tubercles (5‐20 mm diam.) consisted of a rind (200‐250 μm thick) enclosing a dense coralloid mass of ectornycorrhizas (150‐300 μm diam.) and rhizomorphs (200‐300 μm diam.). The outer rind region was cemented together with an interhyphal matrix of carbohydrate containing embedded lipid deposits. Dolipores were common in the inner rind indicating the fungal component to be a basidiomycete. Mycorrhizas had thin mantles and well‐formed Hartig nets. Protein and lipid reserves were present in mantle hyphae. Rhizomorphs formed around non‐mycorrhizal roots inside the tubercles. The central zone of rhizomorph tissue contained thick‐walled hyphae which stained positively for lignin‐like material. The tubercles are similar to structures formed in associations between Rhizopogon and conifers in the northern hemisphere.
Vesicular‐arbuscular mycorrhizas and the soil‐disturbance‐induced reduction of nutrient absorption in maize.
Authors: FAIRCHILD M. H. , MILLER G. L. 
Published: April 2006

SUMMARYMaize seedlings have been shown to absorb more phosphorus (P) from soil from long term zero‐till plots than from the same soil after disturbance, apparently because of greater vesicular‐arbuscular (VA) mycorrhizal colonization in the undisturbed soil, A growth room experiment was conducted to determine the effect of soil P availability on this phenomenon. Maize was grown for three 3‐week cycles in initially disturbed soil. Phosphorus was mixed with the soil to create five P‐amendment rates: 0, 40, 80, 120, and 160 μg Pg−1soil. After each growth cycle, the soil in half the pots was disturbed and replanted, whereas the other half were replanted without disturbing the soil. In the third growth cycle, shoot dry weights were greater in the undisturbed soil than in the disturbed soil at the lower P‐amendment rates, but soil disturbance had no effect at the 120 and 160 μg P g−1soil amendments. Mycorrhizal colonization was much greater in the undisturbed soil at all P amendment rates. Shoot N, P, Mg, and Zn concentrations were higher in the undisturbed than in the disturbed soil at all P amendments, but only the increased P and Zn could be directly related to increased mycorrhizal colonization. While the benefit to the plant from mycorrhizal colonization induced by lack of soil disturbance can be quite large even at high rates of P amendment to the soil, the benefit achieved depends on the balance between the carbon (C) cost and P benefit to the host and may or may not favour the host.
K+(Rb+) uptake by intact Taraxacum plants: effects of nutrient status on K+uptake
Authors: HOMMELS C. H. , PRINS H. B. A. , KUIPER P. J. C. , TANCZOS O. G. 
Published: April 2006

SUMMARYMicrospecies of the genus Taraxacum differ in mineral ecology, spanning a range from nutrient‐poor and undisturbed soils to heavily fertilized grasslands. In this study, the principal features of K+uptake in Taraxacum plants were surveyed in order to design an appropriate test for an ecological study of K+uptake kinetics.Mechanical stimuli induced transient K+efflux, combined with an alkalinization of the ambient solution; during this period, K+(Rb+) uptake was strongly inhibited. As a consequence, uptake experiments were conducted with intact plants in conditions of minimal disturbance.K+uptake was studied as a function of the internal K+status, which was manipulated by various (pre)treatments including cultivation at different temperatures and various types of K+deprivation. NO−3‐dependent K+uptake in ‘high‐salt’ plants was abolished by pretreatments in which K+uptake was inhibited (i.e. cultivation in CaSO4 solution, or in complete nutrient solution with K+omitted, or in K2SO4 solution). In K+‐starved plants, NO−3‐dependent K+uptake was replaced by K+/H+exchange.
Characterization of the high‐affinity K+(Rb+)‐uptake system in roots of intact Taraxacum microspecies: comparison of 12 microspecies in relation to their mineral ecology
Authors: HOMMELS C. H. , SAAT T. A. W. , KUIPER P. J. C. 
Published: April 2006

SUMMARY Taraxacum microspecies differ with respect to nutritional levels in their habitats. In the context of marked differences in growth response to internal potassium concentration between two ecologically contrasting microspecies, K+‐uptake characteristics, Vm and Km, of the high‐affinity uptake system of 12 microspecies were studied. In this comparative study, CaSO4‐pretreated plants were used.Microspecies differences in Vmax were more abundant than in Km. Significant differences between kinetic parameters of ecologically related groups of microspecies were largely absent; only the (average) Vmax of the group of microspecies derived from heavily fertilized and moist grasslands was higher than those of the remaining three groups of microspecies. Within a taxonomically related group of eight microspecies, variation in Vmax (average) and Km (average) values was almost as high as total variation. The results on kinetic characteristics of the high‐affinity K+‐uptake system are discussed in the context of additional differences in physiology such as the critical internal K+concentration and growth potential between two representative microspecies of different mineral ecology.
The influence of ozone, acid mist and soil nutrient status on Norway spruce [Picea abies (L.) Karst.]
Authors: BARNES J. D. , EAMUS D. , BROWN K. A. 
Published: April 2006

SUMMARYThree‐year old Norway spruce [Picea abies (L.) Karst.] trees established from two clones (4076 and 2470) of a medium‐altitude southern German provenance, were transplanted in May 1986 into two acid brown earth soils which differed particularly in the amounts of exchangeable Ca2+and Mg2+. During the summers of 1987 and 1988 trees were exposed in large‐scale fumigation chambers (solardomes) to ozone at 200 or 40 μg−3(control). Each day trees were treated with acid (pH 3‐6) or control (pH 5‐5) mist solution. In late autumn 1988 certain aspects of tree water relations were investigated. In clone 4076 ozone and acid mist reduced stomatal conductance in the light, but resulted in incomplete stomatal closure at night, reducing the diel range of stomatal conductance in treated trees grown on both soils. In addition, current year's needles excised from clone 4076 dried more rapidly following exposure to ozone and/or acid mist than needles from control trees, indicating impaired stomatal performance. However, evidence of both clonai and soil variation in this response was found. Cellular water relations of current year's shoots of clone 4076 were investigated using pressure‐volume analysis. Exposure to ozone and/or acid mist resulted in a marked increase in the plasticity of tissues (reduction in ɛ) compared with controls, indicating that the pollutants induced cell wall loosening. In trees exposed to acid mist this was associated with lower cellular solute concentrations and a decrease in maximum turgor. Throughout this study, where interactions between ozone and acid mist were significant, they were always antagonistic. It is concluded that effects of ozone and acid mist on stomata, which would be expected to enhance the sensitivity of trees to drought and winter desiccation, may be at least partially compensated for by concomitant changes in the turgor relations of individual cells. It remains to be established whether interactions between gaseous air pollutants and water stress are a factor contributing to the development of forest decline in central Europe and north eastern America.
An ozone‐low temperature interaction in loblolly pine (Pinus taedaL.)
Authors: CHAPPELKA ARTHUR H. , KUSH JOHN S. , MELDAHL RALPH S. , LOCKABY B. GRAEME 
Published: April 2006

SUMMARYLoblolly pine (Pinus taedaL.) seedlings from two families differing in ozone sensitivity, were exposed to ozone and acidic precipitation in modified open‐top chambers, beginning in May of 1988. Visible injury (bleached needle tips) occurred after a late‐season frost in April, 1989 on newly emerging (length 5 cm) needles. After one week, needle tips turned brown and necrotic. Incidence of injury was recorded in April, May and June, 1989. Injury only occurred on trees exposed to ozone at above‐ambient concentrations (1.7 and 2.5 × ambient), and was significantly greater in the ozone‐sensitive family (GAKR 15‐91) suggesting that this response is under some genetic control. Incidence of injury decreased with time and was more noticeable in the ozone‐tolerant family (GAKR 15‐23). There was no effect of acid rain, or interaction between ozone and acid rain, revealed by visible injury. In addition, experiments were conducted to determine if ozone and/or freezing temperatures enhanced electrolyte leakage. There were no differences observed in diffusate conductivity among treatments. These findings suggest that the observed injury was due to photo‐oxidation induced by an ozone‐low temperature interaction, and represent the first report of this type of injury in loblolly pine.
The biology of mycorrhiza in the Ericaceae
Authors: SHAW G. , LEAKE J. R. , BAKER A. J. M. , READ D. J. 
Published: April 2006

summaryThe role of the ericoid mycorrhizal endophyte Hymenoscyphus ericae (Read) Korf & Kernan in the regulation of iron uptake by ericaceous plants is investigated. Growth of the fungus is not inhibited in solution cultures containing a range (0–144 [ig ml−1) of iron concentration ([Fe]ext) typical of those obtained in extracts from heathland soil. Absorption of iron by the fungus occurs rapidly at low [Fe]ext but more slowly as [Fe]ext increases. Concentrations of iron in the mycelium ([Fe]mye), reach 6000μg g−1dry weight. Mycorrhizal (M) roots of Vaccinium macrocarpon Ait. and Calluna vulgaris L. (Hull) showed a very high affinity for iron at low [Fe]ext, a feature not shown by non‐mycorrhizal (NM) roots. The involvement of a hydroxamate siderophore in the absorption of Fe by M plants at low [Fe]ext is suggested.Concentrations of iron in shoots ([Fe]ext of NM plants of V. macrocarpon increase linearly with increasing [Fe]ext while those of M plants fall in the mid‐range of [Fe]ext relative to initial and final values. Ratios of [Fe]extto [Fe]ext are lower in M than in NM plants across the range of [Fe]ext examined. The extent of involvement of mycorrhizal infection in excluding the metal from shoots as [Fe]ext increases, is discussed, and the importance of the mechanisms of iron capture and storage in the root are assessed in terms of iron availability in natural heathlands.
Phosphorus relationships and production of extrametrical hyphae by two types of willow ectomycorrhizas at different soil phosphorus levels
Authors: JONES MELANIE D. , DURALL D. M. , TINKER P. B. 
Published: April 2006

summaryThere is much circumstantial evidence for a role of increased P uptake in the growth response of plants to ectomycorrhizas. Full response curves with and without mycorrhizal infection along a P gradient in soil are, however, required to test this hypothesis fully. In this experiment, rooted cuttings of Salix viminalis L. cv. Bowles Hybrid were grown in a 1:2 mixture by volume of gamma‐irradiated soil and sterile sand, with bicarbonate‐extractable P concentrations of 4, 6, 10, 21, 60 or 90 mg P kg−1. The cuttings were inoculated by mixing peat/vermiculite spawn of Laccaria proxima (Boud.) Pat., or Thelephora terrestris (Ehrh.) Fr., or autoclaved spawn 1: 5 by volume with the soil: sand mixture. The plants showed a positive growth response to mycorrhizal infection by either fungus at the two lower P levels, and to L. proxima only at 10 mg P kg−1. At 21 mg kg−1and above, infection was reduced and neither mycorrhizal inoculation nor further P additions caused significant growth increases. These results imply that the growth responses to ectomycorrhizas in this experiment were solely due to increases in P uptake. Cuttings infected with L. proxima tended to be larger than those infected by T. terrestris. Estimates of percent mycorrhizal infection did not differ between the fungi at the lower P levels. However, overall production of extramatrical hyphae per gram of soil was highest in soil inoculated with L. proxima. At 10 mg P kg−1the length of L. proxima hyphae per unit length of mycorrhizal root, P uptake per unit root weight, and total P content in plants infected with L. proxima were significantly higher than for T. terrestris. This study confirms that increased P uptake can be an important component of growth stimulation by ectomycorrhizas. It also presents the first quantification of extramatrical ectomycorrhizal hyphae in soil and suggests a role for them in the growth response.
Carbon–sink stimulation of photosynthesis in Douglas fir seedlings by some ectomycorrhizas*
Authors: DOSSKEY M. G. , LINDERMAN R. G. , BOERSMA L. 
Published: April 2006

summaryDouglas fir [Pseudotsuga menziesii (Mirb.) Franco] seedlings responded differently regarding rate of photosynthesis when inoculated with three different ectomycorrhizal fungi. Rhizopogon vinicolor FSL788‐5 caused a significant increase in net photosynthesis rate compared to non‐mycorrhizal controls, while Hebeloma crustuliniforme HeCr2 and Laccaria laccata S238‐A had no effect. Colonization by Rhizopogon and Hebeloma caused increased osmotic potential in the leaf symplast compared to controls, while Laccaria did not. Colonization levels for Rhizopogon, Hebeloma and Laccaria were 36, 93 and 73 % of root tips, respectively. Rhizopogon and Hebeloma produced abundant extramatrical hyphae and/or rhizomorphs, while Laccaria was smooth‐mantled. Hebeloma‐colonized seedlings were significantly smaller than non‐mycorrhizal controls; Rhizopogon seedlings were smaller, but significantly so only at P < 0.10. Laccaria did not affect seedling size. Only smaller Hebeloma seedlings exhibited elevated concentrations of N, P, K, and Ca over non‐mycorrhizal controls. These data demonstrate a non‐nutritional basis for increased rate of photosynthesis caused by some ectomycorrhizal fungi that can be explained by the increased photosynthate sink generated by extensive fungal growth associated with the mycorrhizas.