Glossary of "Plant Biology (1st ed.)" by Graham et al. (2003)
- The smallest possible unit of an element that has all of the properties of that element; composed of a nucleus of subatomic particles (protons and neutrons) surrounded by a cloud of orbiting electrons.
- Graham, L. E., Graham, J. M. & Wilcox, L. W. 2003. Plant Biology. -xxxv + 497 pp. Pearson Education, Inc., Upper Saddle River.