Nitrogen-fixing root nodule (Faba vulgaris) Science Image

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Nitrogen-fixing root nodule. Light micrograph of a section through a root nodule of a broad bean plant (Faba vulgaris) showing the symbiotic Rhizobium leguminosarum bacteria (purple) within it. These bacteria are able to convert inert atmospheric nitrogen into ammonia, which can then be converted into other nitrogenous compounds essential for plant metabolism. The presence of the symbiotic bacteria in the roots of the bean plant allows it to grow in nitrogen-poor soils, which are unable to support many other plants. Nitrogen-fixing plants are widely grown in agriculture to return nutrients to soil after they have been depleted by the growth of other crops. Magnification: x35 when printed 10cm wide.