Cowpea Enzymes (IMAGE) American Society of Agronomy Caption These tubes and the centrifuge are used to separate out the antioxidant enzymes to determine the amount each plant made in response to the salicylic acid treatment. Credit Photo credit Wellison Dutra. Usage Restrictions Please 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.