Flax guaiacol peroxidases can be used to illustrate the possibility of misinterpreting the effects of stress on the activity of developmentally regulated enzymes

Peroxidase is implicated in the regulation of plant growth and development and the physiological significance of its isozymes is a central question in the study of this plant enzyme. Stress treatments which concomitantly induce altered activity and altered development give insights into the relationships between peroxidase activity and developmental processes. However, these treatments may also induce changes in development by processes that are completely independent of peroxidase. When this occurs, because the activities of the isozymes are themselves developmentally regulated, there should be changes in the activities of the isozymes which simply reflect the indirect effects of altered development. Thus, it is possible for the treatments to have both direct and indirect effects on activity and stress-induced changes in isozyme activity which are accompanied by changes in growth or development should be interpreted with caution. This paper describes the difficulties of interpreting peroxidase activity data from experiments in which zinc and cadmium treatments were used to induce stress in flax (Linum usitatissimum) seedlings. A method of adjusting the data, to examine induced changes in isozyme activity attributable to effects other than altered development, is described. Applying this method illustrated that some aspects of the data might be misinterpreted if the potential effects of altered development on activity are not taken into account. The problems addressed, and the method used, are generally applicable to developmentally regulated enzymes. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.