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  • Cell & Developmental Biology  (3)
  • Artemisia tridentata  (2)
  • Canopy photosynthesis  (2)
  • 1990-1994  (7)
  • 1
    Electronic Resource
    Electronic Resource
    Effect of competition on stable carbon isotope ratios of two tussock grass species (1991)
    Springer
    Oecologia 88 (1991), S. 148-151 
    Details
    ISSN: 1432-1939
    Keywords: Agropyron desertorum ; Agropyron spicatum ; Pseudoroegneria spicata ; Artemisia tridentata ; Stable carbon isotope composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Previous studies have shown that plant carbon isotope composition varies when plants experience differences in water and nutrient availability. However, none have addressed the effect of root interactions, including competition for these soil resources, on carbon isotope ratios. We studied the effect of interspecific root interactions on the productivity and carbon isotope ratios of two Great Basin tussock grass species (Agropyron desertorum and Pseudoroegneria spicata). We compared grasses grown in mixture with sagebrush (Artemisia tridentara) to grasses in similar mixtures but where root interactions with sagebrush were limited by fiberglass partitions. During both years of the study, tussocks growing in competition with sagebrush produced tissue with more negative δ13C values than grasses experiencing limited root interaction with sagebrush. The magnitude of this difference (0.5 to 0.9%) is similar to that found in other studies when soil fertility and moisture availability were altered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00328416
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  • 2
    Electronic Resource
    Electronic Resource
    Soil solution phosphate, root uptake kinetics and nutrient acquisition: implications for a patchy soil environment (1992)
    Springer
    Oecologia 89 (1992), S. 305-309 
    Details
    ISSN: 1432-1939
    Keywords: Soil phosphate ; Root kinetics ; Root proliferation ; Agropyron desertorum ; Artemisia tridentata
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The importance of increased root phosphate (P) uptake kinetics, root proliferation and local increases of soil solution P (P1) for P acquisition from fertile soil microsites was explored with a simulation model and calculated uptake was compared with experimental data. Based on the partitioning of added P in microsites to P1 and P adsorbed on soil particles and the results of a dual-isotope-labeling experiment (Caldwell et al. 1991a), acquisition of P from the fertile microsites was some 20 X that of uptake from an equal volume of soil which received only water. Simulations were in general agreement and also showed that elevation of root P uptake kinetics could contribute more to the increased acquisition than did root proliferation under these circumstances. Although increased physiological uptake capacity for P has generally been considered to be of little benefit because of diffusion limitation, in patchy soil environments selective elevation of P uptake kinetics in fertile microsites may be of considerable benefit. These tests were conducted in calcareous soil which releases much less P into the soil solution than do many other soils. In many noncalcareous soils the benefits of selective elevation of root uptake kinetics would likely be greater.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317406
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  • 3
    Electronic Resource
    Electronic Resource
    Plant competition for light analyzed with a multispecies canopy model (1990)
    Springer
    Oecologia 82 (1990), S. 374-380 
    Details
    ISSN: 1432-1939
    Keywords: Triticum aestirum ; Avena fatua ; Canopy photosynthesis ; Canopy model ; Light competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The importance of photosynthetic characteristics such as quantum efficiency or carboxylation efficiency for carbon gain of plants competing for light in dense stands is dependent on several environmental factors and structural features of the canopy. A quantitative analysis of photosynthesis of competing plants in mixed stands of wheat and wild oat (Avena fatua L.), a common weed of wheat, involved measuring photosynthetic parameters of individual leaves at different heights in the canopy throughout the growing season. This information combined with detailed assessments of canopy structure was used with a multispecies canopy model to evaluate the importance of different photosynthetic characteristics for carbon gain in this canopy environment. Independent photosynthesis data sets were used to validate predictions of the model. Carboxylation efficiency (CE) and CO2-and light-saturated photosynthetic capacity (AML) were highly correlated and decreased with depth in the canopy for both species. Quantum efficiency (α) did not tend to decrease with depth in the canopy. Sensitivity analyses with the model for whole-plant carbon gain of each species over entire day periods were conducted. These showed that changes in CE and AML had an influence similar to that of changes in α on carbon gain for both species. This was not necessarily expected from single-leaf photosynthetic behavior in response to changes in CE, AML and α. The influence of α is more pronounced in the lower, more shaded portions of the canopy than are changes in CE and AML. Appreciable differences between the species were apparent for carbon gain under different weather conditions. The differences between the species in carbon gain when in competition for light were associated more with structural features rather than with photosynthetic characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317486
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  • 4
    Electronic Resource
    Electronic Resource
    Plant competition for light analyzed with a multispecies canopy model (1990)
    Springer
    Oecologia 82 (1990), S. 560-566 
    Details
    ISSN: 1432-1939
    Keywords: Canopy structure ; Competition for light ; Leaf area index-LAI ; Leaf inclination ; Canopy photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A multispecies canopy photosynthesis simulation model was used to examine the importance of canopy structure in influencing light interception and carbon gain in mixed and pure stands of wheat (Triticum aestivum L.) and wild oat (Avena fatua L.), a common weedy competitor of wheat. In the mixtures, the fraction of the simulated canopy photosynthesis contributed by wheat was found to decline during the growing season and this decline was closely related to reductions in the amount of leaf area in upper canopy layers. For both species in mixture and in monoculture, simulated photosynthesis was greatest in the middle or upper-middle canopy layers and sensitivity analyses revealed that canopy photosynthesis was most sensitive to changes in leaf area and leaf inclination in these layers. Changes in LAI and leaf inclination affected canopy carbon gain differently for mixtures and monocultures, but the responses were not the same for the two species. Results from simulations where the structural characteristics of the two species were substituted indicated that species differences in leaf inclination, sheath area and the fraction of leaf area alive were of minor consequence compared with the differences in total leaf area in influencing relative canopy carbon gain in mixtures. Competition for light in these species mixtures appears to be influenced most by differences in the positioning of leaf area in upper canopy layers which determines, to a great extent, the amount of light intercepted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00319801
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  • 5
    Electronic Resource
    Electronic Resource
    Variant cDNAs encoding proteins similar to the α subunit of chicken CapZ (1991)
    New York, NY : Wiley-Blackwell
    Cell Motility and the Cytoskeleton 18 (1991), S. 204-214 
    Details
    ISSN: 0886-1544
    Keywords: actin-binding ; muscle ; Z-line ; capping ; isoform ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Chicken adult muscle and liver cDNA libraries were screened with a cDNA, α1, previously isolated from a chicken embryo library by screening with antibodies against the α subunit of chicken CapZ. cDNAs with a new coding region, called α2, were found in addition to ones with the α1 coding region. α2 predicts a protein sequence that matches exactly the N-terminal sequence of 5 peptides prepared from CapZ α purified from chicken muscle, while the protein sequence predicted by α1 matches the peptides well, but not exactly. The predicted protein sequences of α1 and α2 are very similar to each other, and they are similar to those of the α subunit of capping protein from Dictyostelium [Hartmann et al., J. Biol. Chem. 163:5254-5254, 1989] and an actin-binding protein from Xenopus [Ankenbauer et al., Nature 342:822-824, 1989]. Other conserved features of the predicted primary and secondary structures are noted. Chicken α1 and α2 are transcribed in all of 7 adult chicken muscle and non-muscle tissues in comparable amounts by Northern analysis. α2 has four poly(A)+ RNA transcripts, one of which is rare in liver. α1 has two transcripts. α1 and α2 are encoded by different single-copy genes by Southern analysis of chicken genomic DNA.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cm.970180306
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  • 6
    Electronic Resource
    Electronic Resource
    Culture perfusion schedules influence the metabolic activity and granulocyte-macrophage colony-stimulating factor production rates of human bone marrow stromal cells (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 147 (1991), S. 344-353 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The metabolic function and GM-CSF production rates of adherent human bone marrow stromal cells were investigated as functions of medium and serum feeding rates. A range of medium exchange schedules was studied, ranging from a typical Dexter culture protocol of one weekly medium exchange to a full media exchange daily, which more closely approximates what bone marrow cells experience in situ. Glucose consumption was found to be significantly higher at full daily exchange rate than at any other exchange schedule examined. However, the lactate yield on glucose was a constant, at 1.8 mol/mol, under all conditions considered. Differential serum vs. medium exchange experiment showed that both serum supply and medium nutrients were responsible for the altered behavior at high exchange rates. Glutamine consumption was found to be insignificant under all culture conditions examined. A change in exchange schedule from 50% daily medium exchange to full daily medium exchange after 14 days of culture was found to result in a transient production of GM-CSF and a change in metabolic behavior to resemble that of cultures which had full daily exchange from day one. These results suggest that both stromal cell metabolism and GM-CSF production are sensitive to medium exchange schedules. Taken together, the data presented indicate that attempts to model the function of human bone marrow in vitro may be well served by beginning with medium exchange schedules that more closely mimic the in vivo physiologic state of bone marrow.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041470221
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  • 7
    Electronic Resource
    Electronic Resource
    IL-1α and TNFα act synergistically to stimulate production of myeloid colony-stimulating factors by cultured human bone marrow stromal cells and cloned stromal cell strains (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 159 (1994), S. 221-228 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Human bone marrow stromal cells repond to stimulation by the monokines IL-1 and TNF by producing colony-stimulating factors such as GM-CSF and G-CSF. In this study we show that IL-1α and TNFα act synergistically to stimulate GM-CSF and G-CSF production by cultured marrow stromal cells. We further show that IL-1α and TNFα synergistically stimulate production of GM-CSF and G-CSF by a clonal stroma-derived cell strain. Although IL-1 and TNF share many of the same biological activities, we show that IL-1α and TNFα have an unequal ability to induce myeloid-CSF production by both cultures, with IL-1α being the more potent inducer. We found that induction by IL-1α and TNFα was independent of cell proliferation. The effect of IL-1α and TNFα on production of the two myeloid-CSFs by the clonal cells was significantly greater than the unfractionated passaged stromal cultures, having the greater effect on G-CSF production. The clonally derived stromal cells constitutively produced colony-stimulating activity, in particular GM-CSF, at levels easily detected by ELISA. These findings show that, in addition to the overlapping and additive activities of IL-1α and TNFα, they can interact synergistically. Our findings further suggest that a small subpopulation of stroma cells may be the major producer of G-CSF in the marrow microenvironment during immune response. © 1994 wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041590205
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