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Responses of apple leaf stomata: a model for single leaves and a whole tree
Author(s) -
THORPE M. R.,
WARRIT B.,
LANDSBERG J. J.
Publication year - 1980
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/1365-3040.ep11580508
Subject(s) - transpiration , stomatal conductance , penman–monteith equation , vapour pressure deficit , conductance , mathematics , range (aeronautics) , flux (metallurgy) , gravimetric analysis , tree (set theory) , sensitivity (control systems) , atmospheric sciences , physics , botany , chemistry , mathematical analysis , biology , materials science , ecology , photosynthesis , evapotranspiration , combinatorics , organic chemistry , electronic engineering , engineering , composite material
. An empirical model of stomatal response to environmental factors was developed from measurements of stomatal conductance ( g s ) 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 ( Q p ) and leaf to air vapour pressure gradient ( D ). The response of Q p was hyperbolic and that to D linear; combining these the equation of the model iswhere g r is a reference conductance, α is the slope of the response to D and β indicates the sensitivity of g s response to Q p . 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 g s 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.