Effect of Cyanide on Acid-induced Elongation in Avena Coleoptiles in High Strength Buffer

Abstract

Summary The question has been raised as to whether the strength of the acid buffer (5 mM succinate) used in our previous studies to demonstrate cyanide inhibition of acid-induced elongation was sufficiently high. In the present experiments cyanide (1 mM) was found to inhibit low pH-induced elongation of peeled Avena sativa, L. var. Victory coleoptile segments at pH 3.5, 4, and 5 by 52, 48, and 63 %, respectively, in high strength buffer (20 mM succinate). These results seem to eliminate the possibility that KCN might be inhibiting acid-induced growth by causing an increase in the wall pH. The fact that cyanide is a respiratory inhibitor is suggestive but does not prove metabolic involvement in cyanide sensitive acid-enhanced growth. The fact that cyanide-treated tissue in osmotic shock experiments exhibited some early decrease of elongation suggests that cyanide is capable of decreasing wall extensibility and/or causing injury to cell membranes.