Regulation of ACC-Dependent Ethylene Production by Excised Leaves from Normal and AlbinoZea maysL. Seedlings

Abstract

Dunlap, J. R. 1988. Regulation of ACC-dependent ethylene production by excised leaves from normal and albino Zea mays L. seedlings.—J. exp. Bot. 39: 1079-1089. Albino corn (Zea mays L.) seedlings lacking natural leaf pigments were obtained by germinating seeds treated with fluridone, an inhibitor of carotenoid biosynthesis. Basal rates of ethylene production were less than 20 nl g_1 fr. wt. h_1 in both treated (albino) and untreated (normal) leaves but increased by 10- to 20-fold in the presence of added ACC. ACC-dependent ethylene production (ADEP) was inhibited by cobalt or cyanide ions and stimulated by NaHC03, C02 and light. ADEP in both tissues was stimulated by glucose, fructose, galactose and sucrose. The accumulation of respiratory C02 did not account for the carbohydrate response. The decline in the ADEP characteristic of albino leaf tissue was slowed by incubation in the presence of sucrose. IAA and ABA stimulated ADEP in normal leaves but inhibited ADEP in albino leaves. Sucrose-stimulated ADEP was inhibited in albino leaf tissue treated with IAA or ABA indicating a possible role for the chloroplast in carbohydrate-facilitated ADEP. However, results from this study suggest that chloroplasts perform a function in the regulation of ethylene production by leaf tissue that extends beyond merely influencing internal levels of C02. In the absence of detectable ACC, EFE was responsible for the entire series of responses expressed in regulation of ethylene biosynthesis by corn seedling leaf tissue.