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

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 2.0 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 NaHCO3, CO2 and light. ADEP in both tissues was stimulated by glucose, fructose, galactose and sucrose. The accumulation of respiratory CO2 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 CO2. 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.