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  • 1
    Electronic Resource
    Electronic Resource
    Responses of apple leaf stomata to environmental factors (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 3 (1980), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Stomatal conductances (gs) were measured on the leaves of 3–4 year old Golden Delicious trees and of seedlings of two other cultivars. Measurements were made on container grown trees in the field with a diffusion porometer in 1975 and 1976, and in controlled conditions in a leaf chamber in the laboratory in 1976. Stomatal densities in the Golden Delicious leaves were assessed from scanning electron micrographs. Stomatal density on extension shoot leaves was higher than on other leaf types after June.The response to irradiance shown by both the porometer and the leaf chamber results could be described by a rectangular hyperbola: 〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:01407791:PCE13:PCE_13_mu1"/〉where gmax is maximum conductance and β indicates the sensitivity of gs to photon influx density (Qp). The values of β were in the range 60–90 μmol m−2 s−1.There was no evidence that apple stomata are sensitive to temperature per se, but gs was reduced by increasing leaf to air vapour pressure deficits (D). There was a linear relationship between gs and D which was not attributable to feed-back to leaf water potential (ψL) as the latter did not affect gs until a threshold of about −2.0 to −2.5 MPa was reached. Conductance generally declined with increasing ambient CO2 concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11580397
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  • 2
    Electronic Resource
    Electronic Resource
    Responses of apple leaf stomata: a model for single leaves and a whole tree (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 3 (1980), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. An empirical model of stomatal response to environmental factors was developed from measurements of stomatal conductance (gs) made in a leaf chamber under controlled conditions. Results presented in a companion paper (Warrit, Landsberg & Thorpe, 1980) indicated that the model could be written in terms of only two factors, photon flux density (Qp) and leaf to air vapour pressure gradient (D). The response of Qp was hyperbolic and that to D linear; combining these the equation of the model is〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:01407791:PCE23:PCE_23_mu1"/〉where gr is a reference conductance, α is the slope of the response to D and β indicates the sensitivity of gs response to Qp. Values of α were 0.20 and 0.30 kPa−1 in June and August; the corresponding values of β were 59 and 79 μmol m−2 s−1.The model was tested against mean values of gs obtained with a porometer in the field, using environmental measurements as inputs. Correspondence between measured and calculated values was good. Transpiration rates were calculated from the Penman-Monteith equation, with stomatal resistance values calculated from the model, and compared with gravimetric measurements of tree water use. It was shown that transpiration could be calculated with acceptable accuracy. The effects of variations in stomatal resistance on transpiration rates under a range of conditions were explored using the model and the Penman- Monteith equation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11580508
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  • 3
    Electronic Resource
    Electronic Resource
    Photosynthetic characteristics of the leaves of ‘Golden Delicious’ appletrees (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 1 (1978), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Using an open-system leaf chamber, gas exchange measurements on attached leaves of 3-4-year-old Golden Delicious apple trees, made through two seasons, provided data from which the parameters of a leaf photosynthesis model could be derived. The equation is: 〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:01407791:PCE51:PCE_51_mu1"/〉where C1 is internal CO2 concentration and Qp is the incident quantum flux. There was considerable leaf to leaf variation in the values of the parameters but no clear seasonal trends were established. The initial slope (a) had an average value of about 2.5 × 10−3 mg μmol−1† (i.e. quantum yield ∼ 0.057); the mesophyll conductance (gm) was about 3.5 mm s−1 in extension leaves of trees carrying fruit and 2.5 mm s−1 in extension leaves of defruited trees. Differences between the values of gm for spur leaves with and without subtending fruits were not significant; 2.5 mm s−1 may be used. Dark respiration (Rd, mg m−2 s−1) increased exponentially with temperature (T°C); Rd∼ 0.006 exp (0.09 T). At saturating photon flux density Pn was linearly related to Ci, up to Ci∼ 250 mg m−3. Optimum temperatures for Pn were slightly different in the two years and were in the range 16-26°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1978.tb00746.x
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  • 4
    Electronic Resource
    Electronic Resource
    THE MATHEMATICS OF PHOTOSYNTHESIS AND PRODUCTIVITY (Book). (1982)
    Oxford, UK : Blackwell Publishing
    Plant, cell & environment 5 (1982), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11611534
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  • 5
    Electronic Resource
    Electronic Resource
    Respiration rates of apple trees, estimated by CO2-efflux measurements (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 4 (1981), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Measurements of the efflux of CO2 from 5–6 year old container grown apple trees, in the dark at a range of temperatures (T), indicated that respiration rate (R) can be described by the equation R = SL e kT. The temperature coefficient k, was the same at all times of the year and for all components of the trees, but the values of a varied. At the same temperature respiration rates were low when the trees were dormant, rose rapidly to a peak in spring (before full bloom) and then declined steadily through the season. When respiration was expressed as a flux density, rates for different components of the tree were usually similar. Differences were sometimes statistically significant but no clear pattern emerged. The results obtained are similar to those published for other plants and the equation can be used in the calculation of the carbon balance of apple trees.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1981.tb01037.x
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  • 6
    Electronic Resource
    Electronic Resource
    Stomatal response to humidity: implications for transpiration (1980)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 3 (1980), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Transpiration rates from apple leaves are analysed in terms of the ratio of latent heat flux (λE) to leaf net radiation (Q1) and the climatological resistance (ri). Increases in stomatal resistance with increasing leaf to air vapour pressure gradient (D), described by an empirical model, are incorporated in the analysis. This humidity effect causes the proportion of energy dissipated as latent heat to fall as Q1 increases, so that leaf transpiration rates in high energy environments are likely to be similar to those in lower energy environments. Boundary layer resistance (ra) exerts an increasingly important effect on transpiration rates as Q1 increases. At constant Q1 stomatal closure in response to increasing D results in very small changes in leaf temperature (T1) across a wide range of ambient vapour pressure deficits (δe); ra is then the major factor determining T1. The implications of these results are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11580512
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  • 7
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    Estimating maximum mean canopy stomatal conductance for use in models (2001)
    Canadian Science Publishing
    Details
    Publication Date: 2001-02-01
    Description: Fertilized (F) and irrigated and fertilized (IF) stands of Pinus taeda L. produced twice the leaf area index of irrigated (I) and control (C) stands. Based on sap flux-scaled mean stomatal conductance (GS), we found that stomatal conductance in F was half that in other treatments. During the growing season, GS was related to vapor pressure deficit (D) and soil moisture. During the cooler season, soil moisture was high and light accompanied D in controlling GS. Under all conditions and treatments, the rate of decrease in GS with D was proportional to GS at low D (= 1 kPa). We evaluated whether GS can be used as an input to growth models and used a simple growth model (3-PG), which also predicts stand transpiration (EC), to compare with direct EC measurements in the four stands. Model predictions of monthly EC based on Penman-Montieth equation parameterized with maximum GS (GSmax) estimated under highest "native" soil moisture (0.07 m3·m3) produced long-term values within 10% of measured EC. When the model was parameterized with GSmax estimated under experimentally raised soil moisture, or with porometrically measured conductance, EC values were consistently overpredicted from 12 to 33%. Thus, sap-flux scaled mean canopy stomatal conductance obtained under non limiting light conditions, low D, and highest native soil moisture, is the most appropriate parameter value for certain single-leaf type of models.
    Print ISSN: 0045-5067
    Electronic ISSN: 1208-6037
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Canadian Science Publishing
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  • 8
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    Generalizing plant-water relations to landscapes (2011)
    Oxford University Press
    Details
    Publication Date: 2011-11-24
    Description: Aims Changing climate and land use patterns make it increasingly important that the hydrology of catchments and ecosystems can be reliably characterized. The aim of this paper is to identify the biophysical factors that determine the rates of water vapor loss from different types of vegetation, and to seek, from an array of currently available satellite-borne sensors, those that might be used to initialize and drive landscape-level hydrologic models. Important Findings Spatial variation in the mean heights, crowd widths, and leaf area indices (LAI) of plant communities are important structural variables that affect the hydrology of landscapes. Canopy stomatal conductance ( G ) imposes physiological limitation on transpiration by vegetation. The maximum value of G ( G max ) is closely linked to canopy photosynthetic capacity, which can be estimated via remote sensing of foliar chlorophyll or nitrogen contents. G can be modeled as a nonlinear multipliable function of: (i) leaf–air vapor pressure deficit, (ii) water potential gradient between soil and leaves, (iii) photosynthetically active radiation absorbed by the canopy, (iv) plant nutrition, (v) temperature and (vi) the CO 2 concentration of the air. Periodic surveys with Light Detection and Ranging (LiDAR) and interferometric RADAR, along with high-resolution spectral coverage in the visible, near-infrared, and thermal infrared bands, provide, along with meteorological data gathered from weather satellites, the kind of information required to model seasonal and interannual variation in transpiration and evaporation from landscapes with diverse and dynamic vegetation.
    Print ISSN: 1752-993X
    Electronic ISSN: 1752-9921
    Topics: Biology
    Published by Oxford University Press
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  • 9
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    Estimation of potential forest productivity across the Oregon transect using satellite data and monthly weather records (2001)
    Taylor & Francis
    Details
    Publication Date: 2001-01-01
    Print ISSN: 0143-1161
    Electronic ISSN: 1366-5901
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Taylor & Francis
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  • 10
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    Generalizing plant-water relations to landscapes (2011)
    Oxford University Press
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    Publication Date: 2011-03-01
    Print ISSN: 1752-993X
    Electronic ISSN: 1752-9921
    Topics: Biology
    Published by Oxford University Press
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