Annals of Botany 64: 707-711, 1989
© 1989 Annals of Botany Company
RESEARCH-ARTICLE |
The Effect of pH on the Action of Respiratory Inhibitors in Avena fatua Seeds
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* Alberta Environmental Centre Vegreville, Alberta T0B 4L0, Canada
Department of Plant Science, University of British Columbia Vancouver, B.C. V6T 2A2, Canada
For correspondence and reprint requests.
Accepted: 24 July 1989
The effects of pH on the action of sodium azide, a cytochome-oxidase inhibitor, and salicylhydroxamate (SHAM), an alternative respiration inhibitor, on the respiration of dormant seeds of wild oat (Avena fatua L.; line AN-51) were studied. While pH had little effect on seed respiration in controls, it strongly affected the activity of azide. One mM azide inhibited seed respiration at pH5, but stimulated it at pH 7. SHAM (10 mM) completely inhibited the stimulation of respiration by 1 mM azide in an unbuffered medium, but failed to do so when the medium was buffered at pH 7. In unbuffered medium, 10 mM SHAM actually augmented the stimulation of respiration by 0.25 mM azide to the same degree as when the azide solution was acidified to mimic the pH change incurred with dissolution of 10 mM SHAM. These results suggest that the inhibitory effect of SHAM on the action of azide in an unbuffered system may in part be due to its acidification of the incubation medium rather than by the inhibition of alternative oxidase. Lower pH favours the formation of the undissociated hydrazoate molecules causing greater inhibition of cytochrome-oxidase and other azide-sensitive enzymes.
Avena fatua L, wild oat, seed dormancy, azide, salicylhydroxamate