Comparison of Glycolipids and Plastids in Callus Cells and Leaves of Alnus and Betula

Abstract

The fine structure of plastids and fatty acid composition of glycolipids (e.g. monogalactosyl diacylglycerides, MGDG; digalactosyl diacylglycerides, DGDG) in callus cells of Alnus glutinosa, A. incana and Betula pendula cultured in light was compared with that in intact leaves. The tissues were qualitatively very similar but a rather high amount oflignoceric acid (24:0) was characteristic for the callus of A. incana. This fatty acid was found only in trace amount in other tissues. Linolenic (18:3) and palmitic (16:0) acids are the most abundant (25–65% and 17–27% respectively) fatty acids in all tissues studied. The proportion of 18:1 and 18:2 was much higher in the callus compared with corresponding intact leaves, which are especially rich (48–65%) in 18:3. In callus cultures a higher proportion (17–19%) of linoleic acid (18:2) is found in both Alnus species than in the two callus strains of Betula (9–12%). All leaf and callus samples contained esterified steryl glycosides and two cerebrosidelike spots in thin-layer chromatography, but they were more prominent in callus cultures than in leaves. The callus cells have plastids with rather well developed thylakoids which explains the similarity of the main glycolipid components (MGDG and DGDG) to that of leaves.