The Effects of Paclobutrazol on Sterol and Acyl Lipid Composition of Membranes in Apium Graveolens and Rhodotorula Gracilis

Abstract

Paclobutrazol is a triazole plant growth retardant which also has fungicidal properties [1]. It is an inhibitor of cytochrome P-450 dependant enzymes such as ent- kaurene oxidase and sterol 14α-methyl-demethylase [1]. The fungicidal activity of azole compounds is believed to result from the inhibition of sterol 14α-demethylation. This causes an accumulation of 14α-methylsterols and loss of ergosterol which may have adverse effects on membrane properties [2]. However, there is evidence for other essential requirements for sterol in cell proliferation in addition to a membrane structural role [3–6].For example, in yeast mutants traces of ergosterol stimulate phospholipid formation [7] and protein kinase activity [8]. This report describes the effects of paclobutrazol on the sterol and phospholipid compositions of membranes from plant and yeast cultures.