A research team led by the University of Washington and Pacific Northwest National Laboratory has shown that microbes taken from trees growing beside pristine mountain-fed streams in Western Washington could make phosphorus trapped in soils more accessible to agricultural crops. The findings were published in October in the journal Frontiers in Plant Science.
Endophytes, which are bacteria or fungi that live inside a plant for at least some of their lifecycle, can be thought of as "probiotics" for plants, said senior author Sharon Doty, a professor in the UW School of Environmental and Forest Sciences. Doty's lab has shown in previous studies that microbes can help plants survive and even thrive in nutrient-poor environments -- and help clean up pollutants.
In this new study, Doty and collaborators found that endophytic microbes isolated from wild-growing plants helped unlock valuable phosphorus from the environment, breaking apart the chemical complexes that had rendered the phosphorus unavailable to plants.
"We're harnessing a natural plant-microbe partnership," Doty said. "This can be a tool to advance agriculture because it's providing this essential nutrient without damaging the environment." Doty's research scientist, Andrew Sher, and UW undergraduate researcher Jackson Hall demonstrated in lab experiments that the microbes could dissolve the phosphate complexes. Poplar plants inoculated with the bacteria in Doty's lab were sent to collaborator Tamas Varga, a materials scientist at the Environmental Molecular Sciences Laboratory at Pacific Northwest National Laboratory in Richland, Washington. There researchers used advanced imaging technologies at their lab and at other U.S. Department of Energy national laboratories to provide clear evidence that the phosphorus made available by the microbes did make it up into the plant's roots.
The imaging also revealed that the phosphorus gets bound up in mineral complexes within the plant. Endophytes, living inside plants, are uniquely positioned to re-dissolve those complexes, potentially maintaining the supply of this essential nutrient.
(Source: Agriculture and Food News, ScienceDaily. www.sciencedaily.com)

Poplar trees such as these along the Snoqualmie River able to thrive on rocky riverbanks, despite low availability of nutrients like phosphorus in their natural habitat. Microbes help these trees capture and use the nutrients they need for growth. Photo Credit: Sharon Doty/University of Washington