A peaceful scene—chirping birds, the whisper of a breeze, the contented crunching sound of little jaws at work. Indeed, a person would be hard put to realize that he's in the midst of a battlefield. But little jaws have to work on something, and those sounds are the opening shots of a blitzkrieg that could spell the end for that "something"—in this case, a wild tobacco plant.
A voracious hawk-moth caterpillar can strip a plant, preventing its
reproduction. And what weapons could a stupid plant have to defend itself with?
Chemicals, that's what. Injured tissues quickly release compounds into the
air—volatiles that send a multifaceted message. While other herbivores are warned that
competitors are present and that chemical defenses are being put in place, insect
predators seeking tasty morsels can detect the call for help from afar. Indeed, these
plants live by the motto that "The enemy of my enemy is my ally". With luck,
enough of the plant survives to set at least a few seeds—and that's really what
it's all about
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
Kessler, A., and I. T. Baldwin. 2001. Defensive function of herbivore-induced plant volatile emissions in nature. Science 291:2141-2144.
Russell, S. A. 2002. Talking plants. Discover, 23(4):46-51, 82.
Sabelis, M. W., A. Janssen, and M. R. Kant. 2001. The enemy of my enemy is my ally. Science 291:2104-2105.