Readings (IMAGE) American Society of Agronomy Caption Freidenreich's research team measured leaf "greenness" as an index of chlorophyll content for each tree over time. This gives them an idea of tree nutrient status between treatments in real time in the field. Credit Ariel Freidenreich Usage Restrictions For use with story only 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.