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  • Stomatal conductance  (3)
  • Photosynthesis (temperature, humidity)  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Stomatal conductance and transpiration of the two faces of Acacia phyllodes (1987)
    Springer
    Trees 1 (1987), S. 110-122 
    Details
    ISSN: 1432-2285
    Keywords: Phyllodes ; Stomatal conductance ; Transpiration ; Water potential ; Acacia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The daily course of stomatal conductance and transpiration was monitored on each separate face of vertical phyllodes of various acacias. The selected phyllodes had a north-south orientation so that one side faced eastwards and the other westwards. The principal measurements were made on Acacia longifolia and A. melanoxylon in Portugal in late summer and autumn, and additional measurements were made on A. ligulata and A. melanoxylon in Australia. In Portugal, irrespective of soil moisture status, conductance showed on early morning maximum with a subsequent gradual decline and sometimes a subsidiary peak in the late afternoon. Maximum conductances appeared to be a function of soil moisture status, whereas the decline in conductance in the late morning and afternoon was correlated with changes in phyllode-to-air vapour pressure deficits rather than changes in phyllode water status. The relationship of transpiration to phyllode water potential did not appear to be influenced by soil moisture status, although transpiration was less in drier soils and in the afternoons, this latter factor contributing to a marked hysteresis in the relationship. The opposing faces of the phyllodes exhibited a high degree of synchrony, showing parallel stomatal opening and closing, despite their large differences in irradiance. Stomatal conductance tended to be higher on the eastern faces in the morning and lower in the afternoon. In A. longifolia the daily average of relative conductance was much the same for both faces, but in A. melanoxylon that of the eastern face was higher and was retained even when the normal orientation of the phyllodes was reversed by turning them through 180°. Synchrony must be achieved by the stomata of both sides responding to common environmental or endogenous signals which are perceived by both surfaces with equal sensitivity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203579
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  • 2
    Electronic Resource
    Electronic Resource
    A model of the gas exchange response ofPicea abies to habitat conditions (1996)
    Springer
    Trees 10 (1996), S. 277-287 
    Details
    ISSN: 1432-2285
    Keywords: Picea abies ; Norway spruce ; Leaf gas exchange ; Net photosynthesis ; Stomatal conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Databases describing branch gas exchange ofPicea abies L. at two montane forest sites, Lägeren, Switzerland (National Forschungsprojekt 14 of the Schweizerische Nationalfonds) and Oberwarmensteinach, Germany (Bayerische Forschungsgruppe Forsttoxikologie), were analyzed in conjunction with a physiologically based model. Parameter estimates for describing carboxylase kinetics, electron transport, and stomatal function were derived, utilizing information from both single factor dependencies and diurnal time course measurements of gas exchange. Data subsets were used for testing the model at the branch level. Most of the observed variation in gas exchange characteristics can be explained with the model, while a number of systematic errors remain unexplained. Factors seen as contributing to the unexplained residual variation and not included in the model are light acclimation, degree of damage in adjustment to pollutant deposition, needle age, and cold stress effects. Nevertheless, a set of parameter values has been obtained for general application with spruce, e.g., for use in calculating canopy flux rates and to aid in planning of focused leaf and canopy level experiments. The value of the model for estimating fluxes between the forest and the atmosphere must be evaluated together with measurements at the stand level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02340773
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  • 3
    Electronic Resource
    Electronic Resource
    A model of the gas exchange response of Picea abies to habitat conditions (1996)
    Springer
    Trees 10 (1996), S. 277-287 
    Details
    ISSN: 0931-1890
    Keywords: Key words Picea abies ; Norway spruce ; Leaf gas exchange ; Net photosynthesis ; Stomatal conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Databases describing branch gas exchange of Picea abies L. at two montane forest sites, Lägeren, Switzerland (National Forschungsprojekt 14 of the Schweizerische Nationalfonds) and Oberwarmensteinach, Germany (Bayerische Forschungsgruppe Forsttoxikologie), were analyzed in conjunction with a physiologically based model. Parameter estimates for describing carboxylase kinetics, electron transport, and stomatal function were derived, utilizing information from both single factor dependencies and diurnal time course measurements of gas exchange. Data subsets were used for testing the model at the branch level. Most of the observed variation in gas exchange characteristics can be explained with the model, while a number of systematic errors remain unexplained. Factors seen as contributing to the unexplained residual variation and not included in the model are light acclimation, degree of damage in adjustment to pollutant deposition, needle age, and cold stress effects. Nevertheless, a set of parameter values has been obtained for general application with spruce, e. g., for use in calculating canopy flux rates and to aid in planning of focused leaf and canopy level experiments. The value of the model for estimating fluxes between the forest and the atmosphere must be evaluated together with measurements at the stand level.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00009649
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  • 4
    Electronic Resource
    Electronic Resource
    Changes in photosynthetic capacity, carboxylation efficiency, and CO2 compensation point associated with midday stomatal closure and midday depression of net CO2 exchange of leaves of Quercus suber (1984)
    Springer
    Planta 162 (1984), S. 193-203 
    Details
    ISSN: 1432-2048
    Keywords: Carboxylation efficiency ; Compensation point (CO2) ; Photosynthesis (temperature, humidity) ; Quercus ; Sclerophyll
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The carbon-dioxide response of photosynthesis of leaves of Quercus suber, a sclerophyllous species of the European Mediterranean region, was studied as a function of time of day at the end of the summer dry season in the natural habitat. To examine the response experimentally, a “standard” time course for temperature and humidity, which resembled natural conditions, was imposed on the leaves, and the CO2 pressure external to the leaves on subsequent days was varied. The particular temperature and humidity conditions chosen were those which elicited a strong stomatal closure at midday and the simultaneous depression of net CO2 uptake. Midday depression of CO2 uptake is the result of i) a decrease in CO2-saturated photosynthetic capacity after light saturation is reached in the early morning, ii) a decrease in the initial slope of the CO2 response curve (carboxylation efficiency), and iii) a substantial increase in the CO2 compensation point caused by an increase in leaf temperature and a decrease in humidity. As a consequence of the changes in photosynthesis, the internal leaf CO2 pressure remained essentially constant despite stomatal closure. The effects on capacity, slope, and compensation point were reversed by lowering the temperature and increasing the humidity in the afternoon. Constant internal CO2 may aid in minimizing photoinhibition during stomatal closure at midday. The results are discussed in terms of possible temperature, humidity, and hormonal effects on photosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397440
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of temperature at constant air dew point on leaf carboxylation efficiency and CO2 compensation point of different leaf types (1985)
    Springer
    Planta 166 (1985), S. 81-88 
    Details
    ISSN: 1432-2048
    Keywords: Carboxylation efficiency ; Compensation point (CO2) ; Photosynthesis (temperature, humidity) ; Sclerophyll ; Transpiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of temperature on photosynthesis at constant water-vapor pressure in the air was investigated using two sclerophyll species, Arbutus unedo and Quercus suber, and one mesophytic species, Spinacia oleracea. Photosynthesis and transpiration were measured over a range of temperatures, 20–39° C. The external concentration of CO2 was varied from 340 μbar to near CO2 compensation. The initial slope (carboxylation efficiency, CE) of the photosynthetic response to intercellular CO2 concentration, the CO2 compensation point (Γ), and the extrapolated rate of CO2 released into CO2-free air (R i) were calculated. At an external CO2 concentration of 320–340 μbar CO2, photosynthesis decreased with temperature in all species. The effect of temperature on Γ was similar in all species. While CE in S. oleracea changed little with temperature, CE decreased by 50% in Q. suber as temperature increased from 25 to 34° C. Arbutus unedo also exhibited a decrease in CE at higher temperatures but not as marked as Q. suber. The absolut value of R i increased with temperature in S. oleracea, while changing little or decreasing in the sclerophylls. Variations in Γ and R i of the sclerophyll species are not consistent with greater increase of respiration with temperature in the light in these species compared with S. oleracea.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00397389
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