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Stomatal response to humidity in a sugarcane field: simultaneous porometric and micrometeorological measurements *
Author(s) -
GRANTZ D. A.,
MEINZER F. C.
Publication year - 1990
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/j.1365-3040.1990.tb01296.x
Subject(s) - stomatal conductance , canopy , cuvette , atmospheric sciences , humidity , environmental science , water vapor , vapour pressure deficit , evaporative cooler , eddy covariance , conductance , transpiration , botany , chemistry , horticulture , photosynthesis , meteorology , mathematics , biology , ecology , physics , optics , organic chemistry , combinatorics , ecosystem
. Gas exchange data obtained with wellventilated leaf cuvettes provide clear evidence of a stomatal response to leaf‐air vapour pressure difference ( V ). In contrast, remotely sensed leaf temperatures with specific assumptions regarding canopy boundary layer characteristics, have been interpreted to mean that stomata do not respond to V. We address this apparent discrepancy in a sugarcane field by simultaneous application of a single‐leaf, porometric technique and a whole‐canopy, Bowen ratioenergy balance technique. These methods indicated significant stomatal response to V in well‐irrigated sugarcane. Stomatal responses to V in the field were obscured by strong covariance of major environmental parameters so that opening responses to light and closing responses to V tended to offset each other. Low boundary layer conductance significantly uncoupled V at the leaf surface ( V s ) from V determined in the bulk atmosphere ( V a ). This reduced the range of the stimulus, V s , thereby reducing the range of the stomatal response, without indicating low stomatal sensitivity to V. Stomatal responses to V a may be smaller than expected from V response curves in cuvettes, since V s rather than the conventionally measured V a is analogous to V in a well‐stirred cuvette. Recently published conclusions that remotely sensed canopy temperatures are inconsistent with stomatal response to V may be based on erroneous estimates of canopy boundary layer conductance and thus of V s , use of air saturation deficit rather than V to express evaporative demand, and investigation at higher levels of evaporative demand than those eliciting maximal stomatal response.