Acetate and Other Carboxylic Acids as Precursors of Ethylene

Abstract

THE fungus Penicillium digitatum, which is the common green mould of citrus fruit, produces a small amount of ethylene which is of physiological significance to its host. The mechanism of ethylene synthesis by the fungus and other plant tissues has been explored in several laboratories by supplying postulated precursors specifically labelled with carbon-14 or tritium. Burg¹ reviewed this work in 1962 and concluded that ethylene is “synthesized fairly directly from sugar, but the steps between glucose and the final product have completely evaded detection”. Wang et al.² have fed specifically labelled sugars and acids to Penicillium digitatum and concluded that an “intimate relationship between ethylene and the tricarboxylic acid cycle is indicated”. Burg and Burg³ provided apple slices with a number of specifically labelled compounds and stated that it is “presumptuous to conclude [that] the relationship [between Krebs cycle acids and ethylene] is very direct”.