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Plant Physiology 72:280-286 (1983)
© 1983 American Society of Plant Biologists

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Articles

Effects of KCN and Salicylhydroxamic Acid on the Root Respiration of Pea Seedlings

Trevor Webb and William Armstrong1

Department of Plant Biology, University of Hull, Hull HU6 7RX, England

Polarography, using cylindrical platinum electrodes, proved suitable for measuring changes in the internal apical O2 concentration of the primary root of pea (Pisum sativum L. cv Meteor) effected by KCN and/or salicylhydroxamic acid (SHAM) in the bathing medium. An electrical rootaeration analog was used to help evaluate some of the results. Concentrations of KCN ≤0.05 millimolar had no significant effect. In response to 0.1 millimolar KCN, the O2 concentration rose substantially for approximately 2 hours, then declined, and after 10 hours had frequently fallen below the pretreatment level. Such changes suggest an initial inhibition of cytochrome oxidase-mediated O2 uptake followed by an induction of the alternative, cyanide-resistant respiratory pathway. These treatments proved nonlethal. Changes in O2 concentration similar to those described for 0.1 millimolar KCN were observed in response to 1 and 10 millimolar KCN but these treatments were lethal and the root apex became soft and often appeared flooded. Roots survived and showed no significant responses when treated with SHAM at concentrations ≤5 millimolar. However, when the alternative pathway had been (apparently) induced by 0.1 millimolar KCN, the addition of 5 millimolar SHAM to the bathing medium caused a substantial and persistent rise in the root apical O2 concentration, suggesting that this (nonlethal) concentration of SHAM could indeed inhibit O2 uptake via the cyanide-resistant pathway.

It is concluded that while O2 uptake normally occurs by the cytochrome pathway in the primary pea root, the alternative, cyanide-resistant pathway can be induced by 0.1 millimolar KCN.

1 To whom reprint requests should be sent.






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ASPB Publications PLANT PHYSIOLOGY THE PLANT CELL
Copyright © 1983 by the American Society of Plant Biologists