The C16:3/C18:3 fatty acid balance in photosynthetic tissues from 468 plant species

Two kinds of plants may be distinguished according to their (n-3) trienoic fatty acid composition in photosynthetic tissues. The cis-7,10,13-hexadecatrienoic acid/cis-9,12,15-octadecatrienoic acid balance directly reflects the biosynthesis pathways (a plastidial one and an extra-plastidial one) of chloroplastic lipids. We analysed the correlation between the existence of these pathways and the evolutionary classification of Cormophytes (particularly Angiosperms). By using cis-7,10,13-hexadecatrienoic acid as a marker for the existence of the plastidial pathway, we studied the overall fatty acid composition of 468 plant species (280 already described in the literature and 188 new ones) distributed among 141 botanical families. The data strongly suggest that the plastidial pathway was lost during evolution and that, in the case of dicotyledonous plants, this loss probably occurred independently and at different rates. The data are also discussed from an environmental and chemotaxonomic point of view. (C) 1998 Elsevier Science Ltd. All rights reserved.