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  • 1
    Electronic Resource
    Electronic Resource
    Analysing partitioning in plants (1983)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 6 (1983), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Our understanding of the control of partitioning in plants and crops is confounded by unsatisfactory and incomplete description of the phenomenon. This paper attempts to improve upon this state of affairs by taking a fresh look at the concepts and the terms we use.While the continued usefulness in general discussion of the popular concepts of source, path and sink and of limitation is recognized, for analysing carbon flows we propose a separate, more practicable and higher level form of description based on a pool: process concept. This is similar to those used to describe the flows of other things in nature. In our analysis of competition between pools, the constant properties pool permeance and pool potential determine partitioning which is a function of the single variable plant potential. A simple phenomenological model embodying them is developed. Because our scheme is less demanding of experimental technique than some, its wide application seems feasible, extending even to the analysis of conventional crop growth measurements. The paper concludes by indicating briefly the sorts of physiological factors which could give rise to these phenomenological properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11611921
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  • 2
    Electronic Resource
    Electronic Resource
    Photosynthesis and transpiration of an isolated tree: model and validation (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. A model for the distribution of radiation incident on leaves in an isolated apple tree is presented. The simulated area of shadow cast by a tree compared well with measured values. The radiation model is combined with leaf models of photosynthesis and stomatal behaviour to simulate diurnal variations in the exchanges of carbon dioxide and water by the tree. Satisfactory correspondence was obtained when observed rates of transpiration and photosynthesis were compared with simulations. Further simulations indicated the diurnal patterns of transpiration and photosynthesis to be expected for trees with various shapes and leaf areas.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1978.tb02039.x
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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
    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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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Correction of infra-red gas analyser readings for changes in reference tube CO2 concentration (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 The theoretical basis for correcting infra-red gas analyser readings for changes in reference tube CO2 concentration is developed, but in practice the corrections made are empirical. Analyser gain (GA) is related to reference tube concentration (A) in hyperbolic manner. The constants in the equation are determined by plotting 1/GA against A. Calibration and operating procedure for a particular type of analyser are described and a numerical example given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1978.tb00747.x
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  • 7
    Electronic Resource
    Electronic Resource
    Heat transfer coefficients for leaves on orchard apple trees (1977)
    Springer
    Boundary layer meteorology 12 (1977), S. 61-73 
    Details
    ISSN: 1573-1472
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The coefficient for heat transfer from apple tree leaves was measured from the energy balance of leaves which were prevented from transpiring by applying ‘Vaseline’ (petroleum jelly). Vaseline had negligible effect on the absorption of short-wave radiation by the leaves. The Nusselt number (Nu) describing heat flux from a leaf in terms of its average temperature was related to Reynolds numbers (Re) in the range 103 to 104 by Nu = 0.46 Re0.54 Pr0.33, where Pr is the Prandtl number. This supports Landsberg and Powell's (1973) wind-tunnel results for transfer from leaves subject to mutual interference.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00116398
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