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The Magnitude of the Stomatal Response to Blue Light: Modulation by Atmospheric Humidity
Sarah M. Assmann and David A. Grantz
Vol. 93, No. 2 (Jun., 1990), pp. 701-707
Published by: American Society of Plant Biologists (ASPB)
Stable URL: http://www.jstor.org/stable/4272885
Page Count: 7
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The effect of leaf-air vapor pressure difference (VPD) on the magnitude of the stomatal response to blue light was investigated in soybean (Glycine max) by administering blue light pulses (22 seconds by 120 micromoles per square meter per second) at different levels of VPD and temperature. At 20 °C and 25 °C, the magnitude of the integrated conductance response decreased with increasing VPD (0.4 to 2.6 kiloPascals), due to an earlier onset of stomatal closure that terminated the pulse response. In contrast, at 30 °C this magnitude increased with rising VPD (0.9 to 3.5 kiloPascals), due to an increasing maximum excursion of the conductance response despite the accelerated onset of stomatal closure. When the feedforward response of stomata to humidity caused steady state transpiration to decrease with increasing VPD, the magnitude of the pulse-induced conductance response correlated with VPD rather than with transpiration. This suggests that water relations or metabolite movements within epidermal rather than bulk leaf tissue interacted with guard cell photobiological properties in regulating the magnitude of the blue light response. VPD modulation of pulse magnitude could reduce water loss during stomatal responses to transient illumination in natural light environments.
Plant Physiology © 1990 American Society of Plant Biologists (ASPB)