Ithaca College

Peter Melcher (Biology) presented the following at UCLA's Department of Ecology and Evolutionary Biology: Discovering Nature Series. Spring 2010.

 "Dying for a good cause - xylem pays the ultimate price for transpiration"

Abstract:

Leaf photosynthetic performance is directly related to leaf water status. The xylem provide the hydraulic connection between water located in the soil and the leaf. Because the hydraulic resistance of this connection impacts the rate of water supply to leaves it has been used to characterize plant adaptations to their environment. In this presentation I will discuss the role of the living and dead cells in translocating fluids from the soil to the leaf. I will also discuss the importance of two non-trivial issues that greatly compromise our ability to fully characterize xylem properties in plants. The first is focused on the role of the living cells in meditating a xylem wound response that causes errors in our estimation of stem hydraulic resistance (by up to 80% in some tree species). 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 also be discussed.