Cycad coralloid roots (IMAGE) University of Guam Caption When cycad coralloid roots are cut open, the blue-green color verifies the presence of nitrogen-fixing cyanobacteria. Credit University of Guam Usage Restrictions None License Licensed content 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 information through the EurekAlert system.