Changes in fatty acid and lipid composition in normal and habituated sugar beet calli

Analysis of fatty acids and other classes of lipids in normal and habituated calli of Beta vulgaris shows that their lipid composition is identical during early stages of culture. However, after 14 days this composition turns out to be very different, as a result of membrane structure modifications during the growth of both types of calli. The fatty acid composition of normal callus remains very stable. The loss of phospholipids during culture is compensated for by increased sterol contents. The normal callus, therefore, seems to maintain its membrane integrity throughout growth. On the contrary, the abundance of free fatty acids and malondialdehyde in habituated callus, even at the juvenile stage, together with a decrease of the unsaturation level of fatty acids during culture are indicative of high lipid peroxidation. Peroxidation of polyunsaturated fatty acids and increases in neutral lipids could generate a loss of fluidity in membranes of habituated callus; the more permeable calli would be unable to maintain their homeostasis. This disturbed cellular homeostasis could be correlated with the vitrified aspect of the habituated callus and its relation with the acquisition of hormonal autonomy could be questioned.