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Abstract Detail



Ecophysiology

Taylor, Sarah [1], Quick, Donald [1], Espino, Susana [1], Schenk, H. [2].

Testing a method for in-situ measurements of stem hydraulic conductance in intact plants.

Hydraulic conductivity of plant stems is a key trait of the hydraulic architecture of plants, with high conductivity typically being associated with high rates of stomatal conductance, transpiration, and photosynthesis. Measurements of hydraulic stem conductance are also essential for standard methods to create xylem vulnerability curves, i.e., the relationship between stem water potential and the percent loss of conductance, and for documenting embolism formation and repair in plants. The main drawback of current hydraulic methods to measure embolisms has been that they are destructive and labor-intensive. The objective of this research was to develop an in-situ system to log hydraulic stem conductance in intact plants in the field for an extended period of time.
Conductance is defined by the flow equation: Conductance equals flow divided by the pressure difference driving the flow. The new in-situ hydraulic conductance measurement system consists of two stem psychrometers for determine the pressure differential along the stem and a volumetric sap flow gage based on the heat balance method, which is placed between the two psychrometers. The system was tested on potted and field-grown Malosma laurina (Anacardiaceae), a chaparral shrub from southern California, and potted Eucalyptus grandis (Myrtaceae) saplings. Hydraulic conductance declined and increased diurnally with stem water potentials, indicating the formation and repair of xylem embolisms. High temperature sensitivity of the stem psychrometers was the main problem encountered during testing of the system, especially when there were large temperature gradients between sapwood and air. We present results from experiments to correct for temperature effects by measuring sapwood temperature gradients using micro-thermistors or measuring plants under temperature-controlled conditions. The new method has great potential for advancing plant hydraulics research in the field.

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1 - California State University, Fullerton, Biological Science, P. O. Box 6850, Fullerton, California, 92834-6850, USA
2 - California State University Fullerton, Department of Biological Science, PO Box 6850, Fullerton, CA, 92834-6850, USA, 626/689-4273

Keywords:
methodology
stem hydraulics
fieldwork
in-situ
sap flow
psychrometer.

Presentation Type: Poster:Posters for Topics
Session: P
Location: Grand Salon A - D/Riverside Hilton
Date: Monday, July 29th, 2013
Time: 5:30 PM
Number: PEP004
Abstract ID:154
Candidate for Awards:None


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