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Stomatal responses to humidity and temperature in darkness
1Biology Department, Utah State University, Logan, Utah 85433-4415, USA. keith.mott@usu.edu
Plant, Cell & Environment
|March 5, 2010
Summary
Stomatal conductance responds strongly to humidity differences between leaf and air, and leaf temperature, regardless of light conditions. These findings clarify how stomata regulate water loss based on environmental factors.
Area of Science:
- Plant Physiology
- Environmental Plant Science
- Plant Anatomy
Background:
- Stomata are crucial pores on plant leaves regulating gas exchange, influencing transpiration and photosynthesis.
- Understanding stomatal responses to environmental factors like humidity and temperature is vital for predicting plant behavior and water use efficiency.
- Previous research has explored stomatal responses, but isolating the effects of humidity and temperature under controlled conditions remains important.
Purpose of the Study:
- To investigate stomatal responses to leaf temperature (T(l)) and ambient (w(a)) and intercellular (w(i)) water vapor mole fractions in darkness.
- To compare stomatal responses in darkness versus light to differentiate humidity effects from photosynthetic influences.
- To elucidate the role of the humidity difference (Deltaw) and leaf temperature in regulating stomatal conductance (g(s)).
Main Methods:
- Measurements of stomatal conductance (g(s)) were conducted in darkness to eliminate confounding effects of photosynthesis and intercellular CO(2).
- Stomatal responses were analyzed concerning variations in ambient water vapor (w(a)), intercellular water vapor (w(i)), and leaf temperature (T(l)).
- The difference in water vapor mole fraction (Deltaw) between ambient air and leaf intercellular spaces was a key variable.
Main Results:
- Stomatal conductance (g(s)) exhibited similar steady-state and kinetic responses to ambient water vapor (w(a)) in both light and dark conditions.
- g(s) showed a pronounced sensitivity to the humidity difference (Deltaw) when w(a) was altered, but less so when w(i) was altered.
- Stomatal apertures responded more sharply to leaf temperature (T(l)) when Deltaw was high (17 mmol mol(-1)) compared to near-zero Deltaw.
Conclusions:
- Stomatal regulation by humidity is largely independent of photosynthetic activity and intercellular CO(2) levels.
- The difference in water vapor concentration (Deltaw) between the leaf and the surrounding air is a primary driver of stomatal response to humidity.
- Leaf temperature significantly influences stomatal aperture, particularly under conditions of substantial atmospheric demand for water vapor.
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