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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 14 (1991), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. A simulation of the quantitative influence of altitude on photosynthetic CO2 uptake capability (AP) included the effects of predicted changes (1) in air temperature (lapse rate) and (2) leaf temperature, (3) ambient pressure and CO2 concentration, and (4) the diffusion coefficient for CO2 in air. When a dry lapse rate (0.01°C m−1) in air temperature was simulated, significant declines (up to 14%) in AP were predicted from sea level to 4km altitude. A moist lapse rate of 0.003°C m−1 resulted in less than a 4% decrease in AP over the same altitude range. When natural leaf temperatures (predicted from heat balance analyses) were simulated, AP was significantly greater (∼20%) than when leaf temperatures were considered equal to air temperature for all lapse conditions. There was virtually no change in AP with altitude when predicted leaf temperatures and moist lapse conditions were simulated. There was a significant (∼10%) increase in AP with altitude when leaf temperature was held constant at 30°C (regardless of altitude) under moist lapse conditions. Future studies evaluating the effects of elevation on photosynthesis could benefit from the above considerations of the effects of natural leaf temperature regimes and prevailing lapse conditions on CO2 uptake potential.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The relative distribution of pooled variance computed at various time scales for records of chromospheric activity has been calculated for approximately 100 stars observed at Mount Wilson Observatory. As shown in Paper I, analysis of the pooled variance provides a technique for estimating the lifetimes of stellar active regions and their influence on chromospheric time series used for determining rotation and activity cycle periods. Pooled variance diagrams may be divided into three morphological types which depend to a large extent on a star's mean level of chromospheric activity (i.e., age) and B-V color (i.e., mass), and possibly depend on star's evolutionary state.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The lifetimes of chromospheric active regions and active region complexes ('active longitudes') for 35 lower-Main-Sequence stars observed at Mount Wilson Observatory are estimated from the relative distribution of pooled variance at different time scales. The time scale of active region evolution (i.e., the lifetime of large active regions) is approximately 50 days, while the lifetime of active region complexes is on the order of 1 year. These estimates can be used to clarify the contribution of active regions to variance in short-term (i.e., 〈1 yr) time series data. Previously unpublished mean rotation periods are documented for several stars.
    Type of Medium: Electronic Resource
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