Glossary of "Plant Biology (1st ed.)" by Graham et al. (2003)
- Nitrogen-containing chemical compounds that have physiological effects on animals, protect plants against herbivory, and are widely used as stimulants (such as the caffeine in coffee or nicotine in tobacco products) or medicines (such as the cancer-treatment podophyllotoxin).
- Graham, L. E., Graham, J. M. & Wilcox, L. W. 2003. Plant Biology. -xxxv + 497 pp. Pearson Education, Inc., Upper Saddle River.