Bacteria in branches naturally fertilise trees: study

Washington: Just like humans, trees too harbour bacteria within them that could provide valuable nutrients to help the plant grow, a new study has found.

The bacteria in and on our bodies have been shown to be vital for human health, influencing nutrition, obesity and protection from diseases, researchers said.

Science has only recently delved into the importance of the microbiome of plants. Since plants cannot move, they are especially reliant on partnerships with microbes to help them get nutrients, they said.

Now, researchers from University of Washington (UW) have shown that poplar trees growing in rocky, inhospitable terrain harbour bacteria within them that could provide valuable nutrients to help the plant grow.

They found that microbial communities are highly diverse, varying dramatically even in cuttings next to each other. The findings could have implications for agriculture crop and bioenergy crop productivity, researchers said.

“This variability made it especially difficult to quantify the activity, but is the key to the biology since it is probably only specific groupings of microorganisms that are working together to provide this nutrient to the host,” said Sharon Doty from UW.

Nitrogen fixation is a natural process that is essential to sustain all forms of life. In naturally occurring low-nutrient environments such as rocky, barren terrain, plants associate with nitrogen-fixing bacteria to acquire this essential nutrient, researchers said.

Nitrogen fixation happens in bacteria-rich nodules on the roots of legumes such as soybeans, clovers, alfalfa and lupines. Bacteria help the roots fix atmospheric nitrogen gas into a form which can be used by the plant, they said.

There is a strongly held belief that only plants with root nodules can benefit from this type of symbiosis. The findings provide the first direct evidence that nitrogen fixation can occur in the branches of trees, with no root nodule required, researchers said.

This could have significant implications for common agricultural crop plants. The microbes which researchers isolated from wild poplar and willow plants help corn, tomatoes and peppers, as well as turf grasses and forest trees to grow with less fertiliser.

Fertilisers are synthesised using fossil fuels, so costs can fluctuate wildly. Because fertilisers are used for growing everything from agricultural and bioenergy crops and trees for lumber to the grass in golf courses, this volatile pricing and uncertain availability affects everyone, researchers said.

“Having access to the key microbial strains that help wild plants thrive on just rocks and sand will be crucial for moving agriculture, bioenergy and forestry away from a dependence on chemical fertilisers and towards a more natural way of boosting plant productivity,” said Doty.

The findings were published in the journal PLOS ONE.

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