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A REDOX-BASED MECHANISM BY WHICH
ENVIRONMENTAL STRESSES ELICIT CHANGES IN
PLANT DEFENSIVE CHEMISTRY
DALE M. NORRIS
642 Russell Laboratories, University of Wisconsin, Madison, WI 53706, USA
INTRODUCTION
It is now clear that most, if not all, lifeforms employ chemicals in communicating with their biotic and abiotic
environments. Higher plants and animals, including insects and humans, may even use many of the same compounds
(Rodriquez and Levin 1976, Norris and Liu 1992, Raina et aL 1992). Quinol-quinone redox couples, e.g., p-hydroquinone/
p-benzoquinone (Fig. 1), are prime examples of such common messengers. Hundreds of ions, free radicals (Packer and
Glazer 1990) and molecules have been shown to be messengers. Alkaloids, flavonoids and terpenoids are families of
compounds which are especially important as messengers (Norris 1986).
0 O- OH
II
II II
0 0 O- OH
"A" "B"
Figure l.--The classical redox couple in physical chemistry, p-hydroquinone / p-benzoquinone.
The development of knowledge about the chemical senses has frequently been quite disconnected among many
scientific disciplines. As a result, limited progress has been made in finding unifying principles. However, for several
decades, I have developed hypotheses pertaining to such unifying principles and tested them experimentally (Norris 1994).
The results of our and others' efforts have allowed me to propose that a common code for chemical communication exists
among lifeforms, and them and their abiotic environments. The proposed name for this code is the Environmental Energy
Exchange (EEE) Code (Norris 1981, 1986, 1988, 1994; Neupane and Norris 1992; Norris and Liu 1992).
In this paper, the essential characteristics of this EEE code, including its underlying sulfhydryl (thiol, -SH) / disulfid_
(-S-S-) -dependent oxidative-reductive, energy-transducing mechanism, are applied to the interpretation of how environmen-
tal stresses elicit changes in plant defensive chemistry.
Stress Alteration Of Phytoehemieal Messages
The chemistry by which plants "communicate" with their herbivores has been classified as either constitutive
(i.e., pre-stress) or inducible (i.e., post-stress). Plant pathologists and plant physiologists created this classification to
Mattson, W.J., Niemel_i, P., and Rousi, M., eds. 1996. Dynamics of forest herbivory: quest for pattern and principle. USD_-X
For. Serv. Gen. Tech. Rep. NC- 183, N.C. For. Exp. Sta., St. Paul, MN 55108.
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