The Choat Lab

Plant Hydraulics and Water Relations

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New paper: Direct test of X-ray microCT against hydraulically measured vulnerability to embolism formation

X-ray microtomography (microCT) cross sections (initial scan) of Eucalyptus camaldulensis stems at increasingly negative water potentials illustrate the spread of embolism (air-filled vessels, dark circles) under drought stress.

Embolism (air-filled vessels, dark circles) spread in Eucalyptus camaldulensis under drought stress.

X-ray microtomography allows us to scan plants noninvasively and at high resolution to examine the state of hydraulic failure in xylem conduits. In our recent article in New Phytologist, we directly compared theoretical estimates of hydraulic conductivity provided by microCT imaging with the loss of conductivity measured with a liquid flow meter. While imaging and hydraulic techniques have been compared before, this is the first time both methods were applied to the very same samples.
We show that results from these techniques corresponded well in a Eucalyptus species. Furthermore, we also describe a method to optimise microCT image analysis while overcoming some common potential constraints of current lab-based microCT systems.

Our results help strengthen X-ray microCT as a reference method for plant hydraulic questions, and introduce a reference-based way to calibrate imaging-based vulnerability analysis.

More information: Visualization of xylem embolism by X-ray microtomography: a direct test against hydraulic measurements

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MicroCT experiment at the Australian Synchrotron

We are currently at the Australian Synchrotron in Melbourne to study the hydraulic vulnerability of Eucalyptus trees to drought-induced embolism. The X-ray microCT facility allows us to non-invasively observe embolism in vessels and scan plants repeatedly during a drought treatment.

Below is a short time lapse clip showing how our study trees are mounted onto the microCT stage (which is operated by a robotic arm) and then rotated during the scan: