Melcher, Peter , Warchocki, Steven .
The impact of xylem wounding on the measure of stem hydraulic resistance.
Plant performance is directly related to plant water status and because xylem hydraulic resistance impacts water supply to leaves it has been used to characterize plant adaptations to environment. Xylem tissue in plants contain both living and dead cells. The cells responsible for the mass flow of sap from roots to leaves are composed of numerous dead hollow conduits. The design of these dead conduits e.g., diameter, length and frequency of bordered pit junctions, greatly impact the resistance of sap moving through them. Measurements of xylem hydraulic resistance generally rely on perfusing solution through excised plant tissue. In this study, two non-trivial issues that greatly compromise our ability to fully characterize xylem properties in plants are discussed. The first issue is focused on the role of the living cells in meditating a xylem wound response that was found to increase stem hydraulic resistance by up to 80% in some tree species (in less than a few minutes from excision). Appropriate measurement protocols have been developed that greatly reduce the impact of xylem wounding on the measure of xylem hydraulic resistance. The second issue deals with the difficulty in measurement error that results from opening non-functional flow paths when hydraulic measurements are made on excised tissues that contain multiple years of xylem growth. Results from a new measurement protocol to deal with this issue will be discussed. These two new protocols should allow us to fine tune our estimates of xylem hydraulic resistance in plants. Also, these methods provide a tool to better understand plant response to xylem wounding, a physiological mechanism used by plants to protect and prevent the spread of pathogen invasion into their water conducting systems. Future studies aimed at understanding the role of both the living and dead cells in long-distance sap transport is pertinent in understanding the full influence that plant hydraulic form has on plant drought adaptations.
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1 - Ithaca College, Biology Department, Center for Natural Sciences, 953 Danby Road, Ithaca, NY, 14850, USA
2 - Ithaca College, Biology, Center for Natural Sciences, 953 Danby Road, Ithaca, NY, 14850, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 551B/Convention Center
Date: Monday, August 2nd, 2010
Time: 3:45 PM