Discovery in legumes could reduce fertilizer use and aid environment

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Washington, March 2 (ANI): New findings by Stanford researchers that reveal the inner workings of nitrogen-producing bacteria living inside legumes such as soybeans could enable scientists to blunt the negative effects of excess nitrogen and aid efforts to make agriculture more sustainable.

Excess nitrogen from fertilizer runoff into rivers and lakes causes algal blooms that create oxygen-depleted dead zones, such as the 6,000 to 7,000 square mile zone in the Gulf of Mexico, and nitrogen in the form of nitrous oxide is a potent greenhouse gas.

But now, researchers at Stanford have found a way to minimize those negative effects.

"We have discovered a new biological process, by which leguminous plants control behavior of symbiotic bacteria," said molecular biologist Sharon Long.

"These plants have a specialized protein processing system that generates specific protein signals. These were hitherto unknown, but it turns out they are critical to cause nitrogen fixation," she added.

The ability of legumes to capture nitrogen from the air and turn it into plant food, or "fix" it, also leaves the soil enriched through the plant matter left after harvesting, creating a natural fertilizer for other crops, which is the basis for crop rotation.

Alternating legumes with other crops has been a major component of agriculture around the world for thousands of years.

Yet until recently, little was known about how nitrogen fixation worked, or why some legumes are efficient at fixing nitrogen and others poor.

The key part of the process that Long's research group uncovered is a plant gene that triggers a critical chemical signal.

Without the signal, no nitrogen gets fixed by the bacteria.

The beneficial bacteria in question reside inside the nodules of legumes such as peas, beans, alfalfa and clover, where they pluck molecules of nitrogen from air in the soil and turn it into ammonia, which feeds the plant.

But even legumes can't flourish without the right symbiotic bacteria.

"When you deal with a natural soil, you are dealing with a lot of complexity. Everything we learn about what makes symbiosis work gives us a tool to understand why, sometimes, symbiosis fails," Long said.

"Plant breeders who are trying to help develop better-adapted plants can now analyze traits such as this. We've given them a new tool," he added.

The more efficient that legumes can be made and the wider the range of environments they can thrive in, the more they can help reduce the need for chemical nitrogen that runs off into water or inks into the groundwater or decomposes into a gaseous form, according to Long. (ANI)

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