SPIE Proceedings [SPIE Third International Conference on Photonics and Image in Agriculture Engineering (PIAGENG 2013) - Sanya, China (Sunday 27 January 2013)] PIAGENG 2013: Intelligent Information, Control, and Communication Technology for Agricultural Engineering - Genetic structure and gene flow in the endangered aquatic economic crop Brasenia schreberi J. F. Gmel. (Nymphaeaceae) in China