ScienceDaily (July 13, 2010) — A tiny, little-understood plant pore has enormous implications for weather forecasting, climate change, agriculture, hydrology, and more. A study by scientists at the Carnegie Institution's Department of Global Ecology, with colleagues from the Research Center Jülich in Germany, has now overturned the conventional belief about how these important structures called stomata regulate water vapor loss from the leaf-a process called transpiration. They found that radiation is the driving force of physical processes deep within the leaf.
Researchers have found that radiation is the driving force of physical processes deep within plant leaves. (Credit: iStockphoto/Chaikovskiy Igor)
Stomata are lip-shaped pores surrounded by a pair of guard cells that control the size of the opening. The size of the pores regulates the inflow of carbon dioxide (CO2 ) needed for photosynthesis and the outflow of water vapor to the atmosphere -- transpiration.
Transpiration cools and humidifies the atmosphere over vegetation, moderating the climate and increasing precipitation. Stomata influence the rate at which plants can absorb CO2 from the atmosphere, which affects the productivity of plants and the concentration of atmospheric CO2. Understanding stoma is important for climate change research.
Current climate change models use descriptions of stomatal response based on statistical analysis of studies conducted with a few plant species. This approach is not based on a solid understanding of the mechanism of stomatal regulation and provides a poor basis for extrapolating to environmental conditions.
"Scientists have been studying stomata for at least 300 years. It's amazing that we have not had good grasp about the regulatory mechanisms that control how much stomata open or close in response to a constantly changing environment," remarked co-author Joseph Berry of Carnegie.
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Read more here/Leia mais aqui: Science Daily
Control of transpiration by radiation
Roland Pieruschka a,b, Gregor Huber a, and Joseph A. Berry b,1
-Author Affiliations
aForschungszentrum Jülich GmbH, Institut für Chemie und Dynamik der Geosphäre, 52425 Jülich, Germany; and
bCarnegie Institution of Washington, Department of Global Ecology, Stanford, CA 94305
Edited* by Olle E. Bjorkman, Carnegie Institution of Washington, Stanford, CA, and approved June 16, 2010 (received for review November 13, 2009)
Abstract
The terrestrial hydrological cycle is strongly influenced by transpiration—water loss through the stomatal pores of leaves. In this report we present studies showing that the energy content of radiation absorbed by the leaf influences stomatal control of transpiration. This observation is at odds with current concepts of how stomata sense and control transpiration, and we suggest an alternative model. Specifically, we argue that the steady-state water potential of the epidermis in the intact leaf is controlled by the difference between the radiation-controlled rate of water vapor production in the leaf interior and the rate of transpiration. Any difference between these two potentially large fluxes is made up by evaporation from (or condensation on) the epidermis, causing its water potential to pivot around this balance point. Previous work established that stomata in isolated epidermal strips respond by opening with increasing (and closing with decreasing) water potential. Thus, stomatal conductance and transpiration rate should increase when there is condensation on (and decrease when there is evaporation from) the epidermis, thus tending to maintain homeostasis of epidermal water potential. We use a model to show that such a mechanism would have control properties similar to those observed with leaves. This hypothesis provides a plausible explanation for the regulation of leaf and canopy transpiration by the radiation load and provides a unique framework for studies of the regulation of stomatal conductance by CO2 and other factors.
plant physiology stomata micrometeorology
Footnotes
1To whom correspondence should be addressed. E-mail: jberry@ciw.edu.
Author contributions: R.P. and J.A.B. designed research; R.P., G.H., and J.A.B. performed research; R.P., G.H., and J.A.B. analyzed data; and R.P. and J.A.B. wrote the paper.
The authors declare no conflict of interest.
↵*This Direct Submission article had a prearranged editor.
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.0913177107/-/DCSupplemental.
Freely available online through the PNAS open access option.
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