1. USDA, ARS, Eastern Regional Research Center, 600 E. Mermaid Lane, Wyndmoor, PA 19038, USA;
2. Present address: The College of Chemistry and Life Science, Zhejiang Normal University, Jinhua, Zhejiang Province, China
3. New Mexico State University, Department of Chemistry and Biochemistry, Las Cruces, NM 88003, USA;
4. Department of Plant Biology, Michigan State University, East Lansing, MI 48824–1312, USA;