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- Title
Stomatal response to humidity in a sugarcane field: simultaneous porometric and micrometeorological measurements.
- Authors
Grantz, D. A.; Meinzer, F. C.
- Abstract
Gas exchange data obtained with well-ventilated leaf cuvettes provide clear evidence of a stomatal response to leaf-air vapour pressure difference (<em>V</em>). 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 <em>V</em>. We address this apparent discrepancy in a sugarcane field by simultaneous application of a single-leaf, porometric technique and a whole-canopy, Bowen ratio- energy balance technique. These methods indicated significant stomatal response to <em>V</em> in well-irrigated sugarcane. Stomatal responses to <em>V</em> in the field were obscured by strong covariance of major environmental parameters so that opening responses to light and closing responses to <em>V</em> tended to offset each other. Low boundary layer conductance significantly uncoupled <em>V</em> at the leaf surface (<em>V</em>s from <em>V</em> determined in the bulk atmosphere (<em>V</em>a). This reduced the range of the stimulus, <em>V</em>s thereby reducing the range of the stomatal response, without indicating low stomatal sensitivity to <em>V</em>. Stomatal responses to <em>V</em>a may be smaller than expected from <em>V</em> response curves in cuvettes, since <em>V</em>s rather than the conventionally measured <em>V</em>a is analogous to <em>V</em> in a well-stirred cuvette. Recently published conclusions that remotely sensed canopy temperatures are inconsistent with stomatal response to <em>V</em> may be based on erroneous estimates of canopy boundary layer conductance and thus of <em>V</em>s use of air saturation deficit rather than <em>V</em> to express evaporative demand, and investigation at higher levels of evaporative demand than those eliciting maximal stomatal response.
- Subjects
HUMIDITY; PLANT canopies; SACCHARUM; SUGARCANE; STOMATA; PLANT transpiration; GAS exchange in plants
- Publication
Plant, Cell & Environment, 1990, Vol 13, Issue 1, p27
- ISSN
0140-7791
- Publication type
Article
- DOI
10.1111/j.1365-3040.1990.tb01296.x