Legume crop could help miners’ soil remediation strategies – study

White lupin. (Image by Manuel M.V., Flickr).

Researchers at the University of Montreal are investigating the properties of the legume crop white lupin (L. albus) as an agent for sustainable soil remediation.

According to the scientists, lupin is an arsenic-tolerant plant that is thought to release chemicals directly into the soil via its roots. However, the nature of these compounds is unknown and hard to study due to the complexity of these belowground interactions.

But in their quest to understand such interactions, the team led by Adrien Frémont developed nylon pouches that could be placed close to roots in the soil to capture exuded molecules without damaging the root system. 

The complex mix of molecules collected from these pouches was analyzed using advanced (metabolomic) chemical profiling to identify the compounds capable of binding metals produced by the Lupin plants in response to high concentrations of arsenic. Some of these metal-binding molecules, phytochelatins, are known to be used internally by plants to deal with metal stress but have never before been captured as exuded into polluted soils.

“We’re really excited to see how matching new root-soil sampling approaches with advanced metabolomic profiling can yield such unexpected discoveries,” Frémont said. “We know that plants can drastically change soil properties and can transform or immobilize soil pollution, but the chemistry underlying how they achieve this, and in particular the makeup and function of root-exuded compounds, is still very much an undiscovered country.”

According to Frémont, the next steps of the research are to branch out into a more detailed analysis of the precise chemical reactions taking place at the root-soil interface, including exploration of different plant species, interactions with microorganisms and the challenge of diverse soil pollution.

In the view of the scientist and his group, these findings are rewarding in revealing that natural mechanisms have evolved in plants to deal with this type of pollution, which has accelerated in the past decades with over 7000 sites contaminated with metals such as arsenic only in Canada, as a consequence of both mining and wood preservative operations.

“Although we’re still only just beginning to scratch below the surface of how these plant root strategies work, as we learn more, we can potentially utilize these natural processes to improve soil health and help to alleviate some of the most persistent anthropogenic damage to our environment,” Frémont said. 

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