U.S. flagAn official website of the United States government
                    Here's how you know **Official websites use .gov**
                            
                            A **.gov** website belongs to an official government organization in the United States.
 **Secure .gov websites use HTTPS**
                            
                            A **lock** (                            
                              A locked padlock                                                      
                            
                            ) or **https://** means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Menu Agricultural Research Service
						
                    U.S. DEPARTMENT OF AGRICULTURE
 Crops Pathology and Genetics Research: Davis, CA
 close



    Research

                    Research Projects
                                    Publications
                                    Collaborations
                                    News
                People

                    Staff Listing
                                    Careers


        


                    Outreach Events
                        UC Davis Picnic Day
                                    Kinders go to College
                                    STEM Girls
                                    Future Scientist Program
                                    Agriculture Future of America
                                    Wallace-Carver Fellowship
                                    Young Scholars Program
                                    Annual Awards Banquet
                    About Us
                        About Us
                                    Our Mission
                                    Principal InvestigatorsSearch small
                    Search
            
            ARS Home
                                About ARS
                                Contact Us




ARS Home Pacific West Area Davis, California Crops Pathology and Genetics Research Research Publications at this Location





- ARS National Programs
- Search for a scientific manuscript
- Search for a research project
- ARS Software
- Programs and Projects
- Collaborations
- Subjects of Investigation
- Publications
- Etiology and Biology of Tree Crop Diseases
- Rice Genetics
- Sustainable Floriculture
- Sustainable Viticulture

Title:   Author  item
                                            SCHENK, JOCHEN - California State Universityitem
                                            ESPINO, SUSANA - California State Universityitem
                                            MENDEZ, ALEJANDRA - California State Universityitem
                                            McElrone, Andrew
  Submitted to: Acta Horticulturae
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 4/25/2013
                                    Publication  Date: 5/28/2013
                                    Publication URL: http://actahort.org/books/991/991_40.htmCitation: Schenk, J., Espino, S., Mendez, A., Mcelrone, A.J. 2013. Limitations in the hydraulic pathway: Effects of xylem embolisms on sap velocity and flow. Acta Horticulturae. 991:323-332.Interpretive Summary:
                                Technical Abstract: Sap flow in plants takes place in the xylem, a hydraulic system that is usually under negative pressure and in which gas and liquid phases are separated by nanoporous, fibrous pit membranes. It has long been known that this system is at risk of drawing gas nanobubbles through these membranes into the xylem sap, a process referred to as “air seeding”. These bubbles then can cavitate and create embolisms. Embolized vessels and tracheids block the hydraulic pathway, reduce hydraulic conductivity, and thereby potentially reduce sap flow. Under drought stress, the number of sap-filled conduits often steadily declines with increasingly negative xylem water potential. It was long thought that removal of embolisms would be physically impossible while the system is transporting water under negative pressure. However, recent research has provided abundant evidence for seasonal and/or diurnal formation and removal of xylem embolisms in many plant species. The number of functioning conduits as well as wood water and gas content can fluctuate over a growing season and often over the course of a day. We review evidence for such changes obtained through hydraulic measurements, cryo-scanning electron microscopy, and high-resolution computed tomography. Loss and gain of functional conduits over time effectively translates into changes in the xylem conducting area. In sap flow research, conducting area is almost universally assumed to be constant over time, but this assumption turns out to be invalid for plants that form and repair embolisms. Temporal changes in the water content of other wood cells also affect the thermal conductivity of wood and therefore sap flow measurements based on heat-fluxes. Measurements of active conducting area and wood water content concurrently with sap flow measurements may be needed for accurate determination of sap flux density and volumetric flow.


Return to top


Connect with ARS Sign up


ARS Home
                            USDA.gov
                            Plain Writing
                            Policies & Links
                            Civil Rights Statements
                            FOIA
                            Accessibility Statement
                            Privacy Policy
                            Non-Discrimination Statement
                            Quality of Information
                            USA.gov
                            WhiteHouse.gov