Synchrotron Imaging 2022

May 3, 2023

As part of our research, we are using advanced, high-resolution, 3D imaging techniques to image the microstructure of live trees and cuttings.

A key technique is the X-ray Micro Tomography (microCT), which we access at the Australian Synchrotron in Melbourne. There, electromagnets accelerate charged particles to produce high intensity radiation, with the exact properties controlled dependent on what imaging is sought. We can image tree saplings, which have a relatively weak contrast, at high resolution in short periods of time.

This video shows a 3D image of a section of a living sapling, showing external and internal features.

Our aim is to visit the Australian synchrotron at least annually to advance our techniques, image quality and understanding of plant anatomy.

Two key highlights from our 2022 visit to the Australian Synchrotron were:

1. We confirmed our ability to resolve internal microstructures. The image below is a 2D slice through a maple stem taken using microCT, showing there solution of gas bubbles / air-filled vessels (black). We could isolate these gas filled vessels, and map them out in 3D space, allowing us to examine their size and distribution. These 3D gas bubbles are highlighted in red in the video.

2D slice through a maple stem taken using microCT.

2. We tested a freeze-thaw rig. Our goal is to develop an experimental rig that allows a sapling to be frozen and unthawed in a controlled manner over several hours, whilst being imaged. In this way we can mimic the natural free-thaw cycles in maple trees that drive sap flow. Our custom experimental rig is installed on a motorised dais at the beamline. To get 3D images, because we can’t turn the beamline (it is massive!), we must move our sample. Our setup is designed to secure the sapling firmly to prevent motion (which creates blurry images), whilst controlling temperature. With this design we were able to achieve a realistic freeze-thaw cycle, but had issues with temperature stability, as well as other technical issues. For this reason we are developing an improved version for our next run at the synchrotron.

Experimental setup showing (a) maple tree fixed in place and (b) model setup showing outer insulation and cooling line (at top). Credit: Jamie Robinson, Matt Rennie