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Plant Physiology 82:236-240 (1986)
© 1986 American Society of Plant Biologists

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Articles

Hydroxamate-Stimulated O2 Uptake in Roots of Pisum sativum and Zea mays, Mediated by a Peroxidase 1

Its Consequences for Respiration Measurements

Koos Spreen Brouwer, Ties van Valen, David A. Day2 and Hans Lambers3

Department of Plant Physiology, University of Groningen, P.O. Box 14, 9750 AA Haren (Gr), The Netherlands

Low concentrations of salicylhydroxamic acid (<5 millimolar) stimulate O2 uptake in intact roots of Pisum sativum. We demonstrate that the hydroxamate-stimulated O2 uptake does not reside in the mitochondria. We also show that the hydroxamate-stimulated O2 uptake is due to the activation of a peroxidase catalyzing reduction of O2. This peroxidase, which can use both NADH and NADPH as a substrate, is stimulated by low concentrations of monophenols, e.g. salicylhydroxamic acid and 2-methoxyphenol. It is inhibited by high (20 millimolar) concentrations of salicylhydroxamic acid, cyanide, and scavengers of the superoxide free radical ion, e.g. ascorbate, gentisic acid, and catechol. In the presence of gentisic acid, O2 uptake by intact pea roots was no longer stimulated by low concentrations of salicylhydroxamic acid. The consequence of the present finding for in vivo respiration measurements is that the use of low concentrations of salicylhydroxamic acid and uncoupler is reliable only in the presence of a suitable superoxide free radical scavenger which prevents activation of the peroxidase. It also confirms that high concentrations of salicylhydroxamic acid (20-25 millimolar) can be safely used in short-term experiments to assess the activity of the alternative path in intact roots.

2 Present address: Botany Department, Australian National University, Canberra City, A.C.T. 2601, Australia.

3 Present address: Department of Plant Ecology, University of Utrecht, Lange Nieuwstraat 106, 3512 PN Utrecht, The Netherlands.

1 Supported in part by the Foundation for Fundamental Biological Research (BION) which is subsidized by the Netherlands Organization for the Advancement of Pure Research (ZWO). D. A. D. was the recipient of a grant from the Netherlands Organization for the Advancement of Pure Research (ZWO) while working on this project.






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ASPB Publications PLANT PHYSIOLOGY THE PLANT CELL
Copyright © 1986 by the American Society of Plant Biologists