Air embolisms exsolving in the transpiration water - the effect of constrictions in the xylem pipes

Date

2007

Authors

Canny, Martin
Sparks, Jed P
Huang, Cheng
Roderick, Michael

Journal Title

Journal ISSN

Volume Title

Publisher

CSIRO Publishing

Abstract

When water flows through a constriction, air can come out of solution (i.e. it can exsolve). This phenomenon is manifested in the transpiration stream of plants. Observations of gas in functioning xylem prompted a hypothesis predicting the daily balance between air and water in wood: a sudden fall in water content at sunrise, followed by an increase in water content during the day. An extended record by time domain reflectometry of volumetric water content (VWC) every 2 h throughout a summer shows the detailed pattern of change of VWC during 25 individual days, giving good agreement with the hypothesis. This hypothesis has wide-ranging consequences for experiments using cut plant parts. Perfusing aqueous solutions through excised xylem also can exsolve air from the water, causing declines in flow. The location of such air was investigated in cryo-fixed perfused vine stems by cryo-scanning electron microscopy. Bubbles formed at residual walls of perforation plates in small vessels, and filled many large vessels. The input surface is revealed as a major source of exsolved air. Precautions to reduce this effect are outlined and discussed.

Description

Keywords

Keywords: Bubbles (in fluids); Transpiration; Wood; Declining xylem flow; Kelso interface; Wood water content; Flow of water; air bubble; exsolution; plant water relations; time domain reflectometry; translocation; transpiration; vine; water content; xylem; Bubbles cryoSEM; De-aerated water; Declining xylem flow; Kelso interface; Perforation plates; Pressure gradient; TDR measurements; Wood water content

Citation

Source

Functional Plant Biology

Type

Journal article

Book Title

Entity type

Access Statement

License Rights

DOI

10.1071/FP06210

Restricted until

2037-12-31