Concurrent measurements of stem density, leaf and stem water potential, stomatal conductance and cavitation on a spaling of Thuja occidentalis L.

Abstract

Abstract Concurrent estimates of stem density, leaf and stem water potential, stomatal conductance and ultrasonic acoustic emissions (cavitations) in an excised sapling of Thuja occidentalis L. were made. As the sapling dehydrated in air, the decline in leaf water potential to about ‐ 2.0 MPa was followed by apparent rehydration of the foliage while the stem showed no sign of rehydration. The rate of acoustic emissions peaked prior to the onset of rehydration which coincided with virtual stomatal closure. There was a significant decline in stem density until maximum foliage rehydration level was reached. From this point, leaf water potential, stem water potential and stem density continued a relatively slow decline while acoustic emission rate and stomatal conductance remained low.Removal of the bark and majority of foliage from the sapling resulted in increased cavitation and more rapid deelines in leaf and stem water potential and stem density.