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Ontario Grain Farmer Magazine is the flagship publication of Grain Farmers of Ontario and a source of information for our province’s grain farmers. 

Research roundup


Researchers discover stress response mechanism in plants
Kyra Lightburn
Plants aren’t psychic, yet they can sense the presence of weeds even before they are out-competed for nutrients and resources. How does this happen?


Researchers at the University of Guelph say it is because of a particular biochemical response to altered light characteristics when weeds are present.

PhD student Andrew McKenzie-Gopsill, Department of Plant Agriculture, and his supervising professor, Dr. Clarence Swanton, have recently discovered changes to levels of singlet oxygen (a particularly high-energy and reactive form of oxygen) in plants under weed pressure, when resource competition is prevented within controlled laboratory trials.
These results can help researchers get closer to understanding how plants interpret light reflected from weeds to induce upward growth at the seedling stage. 

To maximize sunlight interception, seedlings engage in shade avoidance response, says McKenzie-Gopsill.

“The light that is reflected from weeds is different in spectrum than sunlight, and these differences trigger a biochemical stress response in plants causing them to grow tall and spindly. This weakens plants and can ultimately reduce yield,” he says.

Understanding mechanisms of plant-weed competition and tolerance is particularly important. With weed resistance to herbicides on the rise in Ontario and globally, there is a significant push to increase the competitive ability of plants in order to circumvent the resistance issue.

The long-term implications of these findings could guide future plant breeding programs to reduce this stress response, helping to maintain plant vigour in spite of weed competition. This could decrease the need for herbicide management at early stages of plant growth when weeds are most problematic.

“Reducing the reliance on herbicides benefits the environment and farmers’ wallets,” says McKenzie-Gopsill. “Our finding really opens the doors on more research opportunities — it’s a whole new way of looking at weed competition.”

Funding for this research has been provided by the Natural Sciences and Engineering Research Council. •

Research Roundup is provided by members of SPARK (Students Promoting Awareness of Research Knowledge) at the University of Guelph’s Office of Research. For more information, contact a SPARK writer at 519-824-4120, ext. 52667.


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