One of Australia’s most significant pieces of scientific infrastructure – the Australian Synchrotron – is being put to use by an innovative three-state group of multidisciplinary researchers.
Three postdoctoral research fellows are working in a unique GRDC-supported collaboration with scientists at the synchrotron – a national research facility located in Melbourne – to generate new knowledge on soil-plant interactions. But COVID-19 lockdowns have provided additional challenges to establishing their collaborative network.
“Our project leaders – Professor Peter Kopittke from the University of Queensland and Professor Enzo Lombi from University of South Australia – have been extremely supportive of the three of us developing novel ways of sharing samples and analytical time across states,” says Dr Casey Doolette, one of the postdoctoral scientists based at the University of South Australia.
Calcareous soil samples, exhibiting nutrient limitations, were extracted from the Eyre Peninsula, South Australia, and sent to Queensland for plant production and then to the synchrotron where the roots were examined at the imaging and medical beamline (IMBL – an X-ray imaging technique). The intact cores were then sent to SA, where they were sectioned and returned to Melbourne for another analysis. The samples have had to be screened for biosecurity as they cross state borders and have successfully dodged lockdowns themselves.
“The soil samples have travelled more than we have in our first year of operation, but it has meant we are well on the way to establishing necessary methods that will underpin future field-based analysis,” Dr Doolette says.
Dr Casey Doolette developed an interest in the capabilities of synchrotron science in 2010 when she received a GRDC Scholarship to perform experiments at the Stanford Synchrotron Radiation Lightsource and Australian Synchrotron to investigate the biofortification of wheat with foliar-applied selenium. Photo: Brenton Edwards, Stories Well Told
Another of the postdoctoral scientists, Dr Han Weng, says the travel restrictions and lockdowns “limited team movement but not collaboration”.
“I had to remotely start my University of Queensland role in Melbourne, while Dr Helen Hou worked from Brisbane (University of Queensland) but was supposed to start her secondment in Melbourne at the synchrotron. Being locked down in Melbourne allowed me to be the only team member to have physical access to the synchrotron during 2020. I was able to carry out two experiments on soil carbon and helped Dr Hou with her first two experiments on root structure, and I coordinated the logistics for Dr Doolette’s X-ray fluorescence microscopy experiment to follow.”
Dr Doolette says: “The spirit of scientific collaboration of scientists that use the synchrotron is a huge inspiration as we learn from techniques developed from different disciplines.”
Method development
Dr Hou (University of South Australia and the University of Queensland) is using X-rays produced at the IMBL at the synchrotron to obtain three-dimensional images of roots growing directly within large soil cores – all without removing the roots from the soil in which they are growing.
Dr Helen Hou (University of South Australia and University of Queensland) has been integrated into the Australian Synchrotron imaging and medical beamline team, based in Melbourne, where she can access specialist synchrotron expertise for the benefit of the grains industry. Photo:Chris Hall, ANSTO
Dr Hou works closely with Dr Doolette, who is investigating the corresponding distribution of available nutrients in these soils, while Dr Weng (University of Queensland) is investigating the interaction between soil organic matter and root growth.
Together, the researchers are developing new methods using the synchrotron that will then enable them to ‘interrogate’ more soil-plant samples to better understand the interaction between root growth, nutrient distribution and soil organic matter. The objective is to help improve crop management practices.
“Understanding the factors that limit root growth within soils is critical to improving crop yield and profitability. The IMBL allows us to use extremely high-intensity X-rays to examine the soil,” Dr Hou says.
Although X-rays have previously been used to study roots in situ, the new faster and more sensitive approach at the Australian Synchrotron can examine roots in soil cores up to 20 centimetres in diameter – 10 times larger than previously possible – and down to considerable depths (50 to 100cm). Examining undisturbed root distribution in large soil cores allows more-realistic and informative analysis.
Advanced analysis
Dr Doolette has developed an alternative means of analysing soil nutrient distributions using gel-based diffusive gradients in thin-film devices (DGT) and F-ray fluorescence microscopy (XFM) analysis.
Only nutrients that are potentially available for plant uptake accumulate in the gel layer. The DGT can then be analysed to measure nutrient concentrations and distribution in the roots and provide more-reliable information on nutrient availability.
Dr Weng is conducting what is believed to be the first use of synchrotron-based soft X-ray and infrared techniques in soils: “We are examining how changes in organic matter within the soil – for example, changes due to cropping frequency or incorporation of green manures – are related to differences in soil properties and root distribution.”
Diverse skill set
The team brings a diverse skill set to generating new plant production knowledge in a variety of soils using the synchrotron.
Dr Hou holds a degree in information sciences and a PhD in information sciences from Tohoku University in Japan.
“My interest in robotics has led me to this research, with interests in image processing and control engineering. For this project, I can use skills in root segmentation and I can apply my knowledge regarding massive image processing, automated batch processing and parallel processing to hybrid root segmentation algorithms,” Dr Hou says.
Dr Doolette, who has a degree in chemistry, has conducted synchrotron experiments since her honours project at the University of Adelaide, where she investigated the biofortification of wheat with foliar-applied selenium.
“For my PhD in environmental chemistry, I investigated the behaviour, fate and plant uptake of contaminants, specifically nanoparticles, in soil. Following my PhD, I worked for the Australian Government Department of Agriculture, Water and the Environment assessing the potential environmental risks of industrial chemicals.”
Dr Weng holds a degree in environmental sciences from the University of East Anglia (UK) and has a keen interest in soil carbon, various soil ameliorants and their potential roles in climate change mitigation.
“During my PhD at the University of New England, I discovered the mechanisms to improve soil carbon retention in a pastoral system over a decade. Following my PhD, I worked on several GRDC subsoil constraint projects at the NSW Department of Primary Industries and La Trobe University,” Dr Weng says.
The trio meet monthly, virtually, to discuss their findings and are excited to move on to the next step of analysing field-based soil cores to provide a step-change for growers’ management practices.
More information: Helen Hou, h.hou@uq.edu.au; Han Weng, h.weng@uq.edu.au; Casey Doolette, 08 8302 6233, casey.doolette@unisa.edu.au
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