Composição de ácidos graxos em raízes de sorgo sob estresse de alumínio

Abstract

The objective of this work was to determine Al effect on fatty acid composition of roots from two sorghum (Sorghum bicolor (L.) Moench) cultivars with differential tolerance to aluminum. After exposure to Al, roots were collected, lipids extracted and the fatty acid composition determined. Palmitic and, especially, linoleic acid were the major fatty acids identified in the root lipid extracts of both cultivars, regardless of the presence of aluminum. Stearic and oleic acids contents increase only in the tolerant cultivar, while linolenic acid decreased in both cultivars after Al treatment. These changes in fatty acid composition, as well as in the C18-fatty acid double bound index (DBIC18) and in the ratios of unsaturated fatty acid/saturated fatty acid (UFA/SFA) and linoleic acid/palmitic acid (18:2/16:0) indicated of a reduction of the lipid fluidity of the tolerant cultivar, but an increase in the sensitive one. The observed reduction in lipid fluidity in the tolerant relative to the sensitive cultivar suggests of a better capacity of the tolerant cultivar to retain essential ions and metabolites and/or to limit the entry of toxic Al ions into roots.