tag archives: work

ICT PSY1 stem psychrometer: how to apply sensor calibration after recording a dataset

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for the past 2+ years i’ve been working with the PSY1 Stem Psychrometer by ICT International. as with any precision instrument, calibration is a crucial step to ensure good data. however, we’ve found that with some older firmware versions, the PSY1 sometimes just dropped its calibration files and reverted to the generic factory-calibration, which reads at +/- 0.5 MPa absolute precision.
after some discussion with ICT, i’ve put together a little R script that allows the application of calibration parameters to an existing file which was recorded with any (or no) calibration. this way, you can recalculate proper water potential readings from already recorded PSY1 csv-files.

ICT PSY1 stem psychrometer: how to apply sensor calibration after recording a dataset

the complete script, documentation and more are available here: psy-posthoc-calib — bitbucket

[category: science] [tags: , ]

time lapse: microCT scanning at the australian synchrotron

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the brodribb and choat lab groups (read: my colleagues and i) are currently at the australian synchrotron in melbourne for an experiment to study what’s going on in the stems and roots of living trees during drought. using x-ray microCT, we can look inside the wood and examine whether vessels are functional (i.e. water-filled) or blocked, without cutting into the tree (which can create a range of problems for measurement).
here’s a time lapse video showing how our eucalyptus trees are mounted onto a high-tech robot arm (0.0001 mm precision movements!), centered, and then rotated during the x-ray scan:

the resulting microCT scans have a resolution of 10 micrometers per pixel and can be reconstructed to 3D models. more about that in a future post…

[categories: science, time lapse] [tags: , , ]

non-invasive imaging of the plant water transport system using x-ray microCT

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it’s been rather quiet in the blog lately, so i thought i’d share a peek into what we’ve been up to at work:

Hydraulic vulnerability analysis using X-ray microCT
MicroCT cross section of a Eucalyptus stem. One of the major points of critique for hydraulic measurements of xylem vulnerability and embolism is that they are destructive measurements. In contrast, non-invasive imaging has made it possible to observe xylem function and the spread of embolism in living, intact plants without destructive sampling and associated artefacts.

In collaboration with Iain Young and Richard Flavel at the University of New England, Armidale, we recently scanned the stems of young Eucalyptus trees at high resolution using X-ray Micro Computed Tomography (microCT) to visualize the loss of hydraulic function at increasing levels of drought. [more...]