WHEN a legume root is infected by the nodule organism ... in a study of the action of the bacterial secretions upon root-hair growth.

Bacteria inside root nodules need oxygen to survive. A pink or red color inside a nodule indicates the oxygen supply is robust and the bacteria are thriving. Disclaimer: AAAS and EurekAlert!

This image depicts root nodules. Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any ...