Document: JOH-3-19-3
Hydraulic architecture and stomatal action.
SPERRY, J.S.* 1, R.OREN 2 and J.P.COMSTOCK 3
University of Utah, Salt Lake City, UT USA 1
Duke University, Durham NC USA 2
Boyce Thompson Institute for Plant Research, Ithaca, NY, USA 3
Abstract:
Ecophysiologists strive to understand variation in stomatal regulation because it is a major determinant of carbon acquisition and productivity. Our understanding of stomatal action is advanced by recognizing the role of hydraulic properties of plant and soil in determining the transpiration rate from leaves and thus indirectly the stomatal conductance for carbon dioxide uptake. While it is often stated that stomata regulate transpiration, it is more accurate to say that stomata regulate plant water status. In doing so, they limit the driving force available for water movement through the plant. The transpiration rate at that driving force is determined by hydraulic conductance of the soil-plant continuum. These basic relationships mean we can predict the response of plant water use to architectural and environmental parameters. Examples include stomatal responses to vapor pressure deficit, soil moisture, soil porosity, rooting depth, root-to-shoot ratio, leaf-to-sapwood ratio, shading, and plant size. These predictions are unaffected by the particular mechanism by which stomata respond to water status. However, they are only as valid as our knowledge of the hydraulic "architecture" of plants, a term originally applied by M.H. Zimmermann to reflect the influence of shoot and xylem structure on canopy water supply. Some areas where further research is needed are the hydraulics of root system structure and its interface with soil, dynamics of hydraulic conductivity in vascular and non-vascular tissues, contributions of capacitance, and scaling rules for hydraulic design. Developing explicit linkages between environment, physiological function, and plant form will allow a more mechanistic approach towards defining plant functional types, analyzing trade-offs between form and function, and predicting responses of vegetation to environmental change.
Keywords: stomatal conductance, plant water use, hydraulic architecture, plant water relations, hydraulic conductivity, plant-soil relationships
This abstract is being presented at: 8:50 AM in session:
Symposium # 9: The Water Limitation: Issues in Plant, Community, and Ecosystem Water Use.