Taking a sample of walnut tree (IMAGE) University of Tennessee Institute of Agriculture Caption Graduate student Aaron Onufrak takes a sample of a walnut tree in preparation for his research. Photo by D. Hadziabdic, courtesy UTIA Credit Photo by D. Hadziabdic, courtesy UTIA Usage Restrictions None License Original 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.