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101.
In a pot experiment, the growth and the nutrient status of in vitro propagated coffee (Coffea arabica L.) microcuttings were investigated for 5 months following vesicular-arbuscular mycorrhizal (VAM) inoculation with either
Acaulospora melleae or Glomus clarum at four soil P availabilities. Control plants remained P-deficient even at the highest soil P availability while mycorrhizal
plants were P-sufficient at all soil P availabilities. Growth of control plants was only improved at the highest soil P availability.
In P-deficient soil, neither of the two VAM species improved plant growth. Plant growth increased by 50% following inoculation
with either A. melleae or G. clarum when P availability went from deficient to low. No further plant growth improvement was induced by either VAM species at
intermediate and high soil P levels. Nevertheless, growth of plants inoculated with G. clarum was still significantly greater than that of non-mycorrhizal plants at the highest soil P availability. Root colonization
by G. clarum increased with increasing soil P availability while root colonization by A. mellea decreased with soil P level increasing above low P availability. Soil P availability also affected Zn nutrition through its
influence on VAM symbiosis. With increasing soil P availability, foliar Zn status increased with G. clarum or decreased with A. mellea in parallel to root colonization by VAM. This study demonstrates the beneficial effects of VAM inoculation on in vitro propagated
Arabica coffee microcuttings, as shown previously for seedlings. This study also demonstrates differences in tolerance to
soil P availability between VAM species, most likely resulting from their differing abilities to enhance coffee foliar P status.
Accepted: 14 November 1996 相似文献
102.
Soils from valley oak (Quercus lobata Nee) riparian areas of the Cosumnes River Nature Conservancy Preserve near Sacramento, California were added to growth medium
of valley oak seedlings grown in a greenhouse or in agricultural fields at Cosumnes which probably once supported valley oak
trees and are now replanted with native riparian vegetation or allowed to revegetate naturally. Agricultural field soil from
the Cosumnes River Preserve was presumed to be low or lacking in ectomycorrhizal inoculum. The study was designed to (1) determine
whether valley oak stand soil transfer could cause mycorrhizal infection on valley oak seedlings in an agricultural field
and in a greenhouse, (2) describe ectomycorrhizal morphological types formed on valley oak seedlings, and (3) determine whether
seedling growth is enhanced more by transfer of natural valley oak stand soil than agricultural field soil. In the field study,
transfer of forest soil increased average ectomycorrhizal diversity (2.4 types) more than transfer of agricultural field soil
(1.2 types). Valley oak seedlings were responsive to ectomycorrhizal infection in the field study. With increase in mycorrhizal
infection there was an increase in shoot growth at the expense of root growth. In the greenhouse study, both percent mycorrhizal
infection and mycorrhizal diversity were increased more by transfer of oak forest and woodland soils than agricultural field
soil. Eight morphotypes occurred on seedlings in forest and woodland soils but only three morphotypes in agricultural soil.
This result strongly suggests that the agricultural field also harbors ectomycorrhizal propagules but forest and woodland
soils support a more abundant and diverse ectomycorrhizal flora.
Accepted: 17 August 1997 相似文献
103.
Morphometry of the human pulmonary vasculature 总被引:2,自引:0,他引:2
Huang, W., R. T. Yen, M. McLaurine, and G. Bledsoe.Morphometry of the human pulmonary vasculature.J. Appl. Physiol. 81(5):2123-2133, 1996.The morphometric data on the branching patternand vascular geometry of the human pulmonary arterial and venous treesare presented. Arterial and venous casts were prepared by the siliconeelastomer casting method. Three recent innovations are used to describethe vascular geometry: the diameter-defined Strahler ordering model isused to assign branching orders, the connectivity matrix is used todescribe the connection of blood vessels from one order to another, anda distinction between vessel segments and vessel elements is used toexpress the series-parallel feature of the pulmonary vessels. A totalof 15 orders of arteries were found between the main pulmonary arteryand the capillaries in the left lung and a total of 15 orders of veinsbetween the capillaries and the left atrium in the right lung. Theelemental and segmental data are presented. The morphometric data arethen used to compute the total cross-sectional areas, blood volumes, and fractal dimensions in the pulmonary arterial and venous trees. 相似文献
104.
Pilot-Scale Selenium Bioremediation of San Joaquin Drainage Water with Thauera selenatis 总被引:1,自引:0,他引:1 下载免费PDF全文
A. W. Cantafio K. D. Hagen G. E. Lewis T. L. Bledsoe K. M. Nunan J. M. Macy 《Applied microbiology》1996,62(9):3298-3303
This report describes a simple method for the bioremediation of selenium from agricultural drainage water. A medium-packed pilot-scale biological reactor system, inoculated with the selenate-respiring bacterium Thauera selenatis, was constructed at the Panoche Water District, San Joaquin Valley, Calif. The reactor was used to treat drainage water (7.6 liters/min) containing both selenium and nitrate. Acetate (5 mM) was the carbon source-electron donor reactor feed. Selenium oxyanion concentrations (selenate plus selenite) in the drainage water were reduced by 98%, to an average of 12 (plusmn) 9 (mu)g/liter. Frequently (47% of the sampling days), reactor effluent concentrations of less than 5 (mu)g/liter were achieved. Denitrification was also observed in this system; nitrate and nitrite concentrations in the drainage water were reduced to 0.1 and 0.01 mM, respectively (98% reduction). Analysis of the reactor effluent showed that 91 to 96% of the total selenium recovered was elemental selenium; 97.9% of this elemental selenium could be removed with Nalmet 8072, a new, commercially available precipitant-coagulant. Widespread use of this system (in the Grasslands Water District) could reduce the amount of selenium deposited in the San Joaquin River from 7,000 to 140 lb (ca. 3,000 to 60 kg)/year. 相似文献
105.
Comparative actions of glutamate and related substances on the lateral line of xenopus laevis 总被引:1,自引:0,他引:1
S C Bledsoe D M Chihal R P Bobbin D N Morgan 《Comp. Biochem. Physiol. C, Comp. Pharmacol. Toxicol.》1983,75(2):199-206
The effects of compounds structurally related to L-glutamate were compared on spontaneous activity of afferent nerve fibres in Xenopus laevis lateral-line. The potencies (EPMR) of several compounds relative to L-glutamate (EPMR = 1) were: L-aspartate (EPMR = 1), D-aspartate (EPMR = 1), D-glutamate (EPMR = 1.98), quisqualate (EPMR = 0.0015), kainate (EPMR = 0.0045), dihydrokainate (EPMR = 0), ibotenate (EPMR = 1.5), L-homocysteate (EPMR = 0.17), 2,4,5-trihydroxyphenylalanine (6-OH-DOPA, EPMR = 0.23), and D-homocysteate (EPMR = 0.73), N-methyl-D,L-aspartate (EPMR = 5), and N-methyl-D-aspartate (NMDA, EPMR = 1). Several compounds, including gamma-aminobutyrate (GABA), suppressed spontaneous activity without eliciting excitatory responses. The results reveal receptors that are present at this vertebrate peripheral synapse. 相似文献
106.
107.
108.
Structural analysis of human neutrophil migration: Centriole, microtubule, and microfilament orientation and function during chemotaxis 总被引:41,自引:21,他引:20 下载免费PDF全文
Orientation of nucleus, centriole, microtubules, and microfilaments within human neutrophils in a gradient of chemoattractant (5 percent Escherichia coli endotoxin-activated serum) was evaluated by electron microscopy. Purified neutropils (hypaque-Ficoll) were placed in the upper compartment of chemotactic chambers. Use of small pore (0.45 μm) micropore filters permitted pseudopod penetration, but impeded migration. Under conditions of chemotaxis with activated serum beneath the filter, the neutrophil population oriented at the filter surface with nuclei located away from the stimulus, centrioles and associated radial array of microtubules beneath the nuclei, and microfilament-rich pseudopods penetrating the filter pores. Reversal of the direction of the gradient of the stimulus (activated serum above cells) resulted in a reorientation of internal structure which preceded pseudopod formation toward the activated serum and migration off the filter. Coordinated orientation of the entire neutrophil population did not occur in buffer (random migration) or in a uniform concentration of activated serum (activated random migration). Conditions of activated random migration resulted in increased numbers of cells with locomotory morphology, i.e. cellular asymmetry with linear alignment of nucleus, centriole, microtubule array, and pseudopods. Thus, activated serum increased the number of neutrophils exhibiting locomotory morphology, and a gradient of activated serum induced the alignment of neutrophils such that this locomotory morphology was uniform in the observed neutrophil populayion. In related studies, cytochalasin B and colchicines were used to explore the role of microfilaments and microtubules in the neutrophil orientation and migration response to activated serum. Cytochalasin B (3.0 μg/ml) prevented migration and decreased the microfilaments seen, but allowed normal orientation of neutrophil structures. In an activated serum gradient, colchicines, but not lumicolchicine, decreased the orientation of nuclei and centrioles, and caused a decrease in centriole-associated microtubules in concentrations as low as 10(-8) to 10(-7) M. These colchicines effects were associated with the rounding of cells and impairment of pseudopod formation. The impaired pseudopod formation was characterized by an inability to form pseudopods in the absence of a solid substrate, a formation of narrow pseudopods within a substrate, and a defect in pseudopod orientation in an activated serum gradient. Functional studies of migration showed that colchicines, but not lumicolchicine, minimally decreased activated random migration and markedly inhibited directed migration, but had not effect on random migration. These studies show that, although functioning microfilaments are probably necessary for neutrophil migration, intact microtubules are essential for normal pseudopod formation and orientation, and maximal unidirectional migration during chemotaxis. 相似文献
109.
Worldwide patterns of mitochondrial DNA differentiation in the harbor seal (Phoca vitulina) 总被引:3,自引:0,他引:3
Stanley HF; Casey S; Carnahan JM; Goodman S; Harwood J; Wayne RK 《Molecular biology and evolution》1996,13(2):368-382
The harbor seal (Phoca vitulina) has one of the broadest geographic
distributions of any pinniped, stretching from the east Baltic, west across
the Atlantic and Pacific Oceans to southern Japan. Although individuals may
travel several hundred kilometers on annual feeding migrations, harbor
seals are generally believed to be philopatric, returning to the same areas
each year to breed. Consequently, seals from different areas are likely to
be genetically differentiated, with levels of genetic divergence increasing
with distance. Differentiation may also be caused by long-standing
topographic barriers such as the polar sea ice. We analyzed samples of 227
harbor seals from 24 localities and defined 34 genotypes based on 435 bp of
control region sequence. Phylogenetic analysis and analysis of molecular
variance showed that populations in the Atlantic and Pacific Oceans and
east and west coast populations of these oceans are significantly
differentiated. Within these four regions, populations that are
geographically farthest apart generally are the most differentiated and
often do not share genotypes or differ in genotype frequency. The average
corrected sequence divergence between populations in the Atlantic and
Pacific Oceans is 3.28% +/- 0.38% and those among populations within each
of these oceans are 0.75% +/- 0.69% and 1.19% +/- 0.65%, respectively. Our
results suggest that harbor seals are regionally philopatric, on the scale
of several hundred kilometers. However, genetic discontinuities may exist,
even between neighboring populations such as those on the Scottish and east
English coasts or the east and west Baltic. The mitochondrial data are
consistent with an ancient isolation of populations in both oceans, due to
the development of polar sea ice. In the Atlantic and Pacific, populations
appear to have been colonized from west to east with the European
populations showing the most recent common ancestry. We suggest the recent
ancestry of European seal populations may reflect recolonization from Ice
Age refugia after the last glaciation.
相似文献
110.