LIPID CHANGES IN COLD HARDENED LEAVES OF NOTHOFAGUS-DOMBEYI

Changes in composition of various lipid fractions of leaves of the woody evergreen Nothofagus dombeyi hardened either under natural (at high and low altitude) or under laboratory conditions were determined. Frost hardiness of the leaves reached a maximum in the cold period (LT5O) - 5° in the lowest place and - 10.2° in the highest site and was associated with an increase in phospholipids and galactolipids. Phosphatidylglycerol, digalactosyldiacylglycerols and monogalactosyldiacylglycerols increased in content by ca 200-400% in winter compared with the summer value. Phosphatidyl inositol concentration decreased in the high altitude samples over the same period. The unsaturation ratio of fatty acids in each lipid fraction was usually higher in summer than that in winter. The proportion of linolenic acid (mol%) of most lipid fractions with respect to the main fatty acids increased in the winter period at both low and high altitude sampling sites. It is possible that the higher proportion of this fatty acid in lipids could help to maintain the fluidity and function of membranes of N. dombeyi during cold stress. This and the accumulation of other described metabolites in this species could explain its pioneer capacity in areas formed by volcanic scoria exposed to strong frost even in summer. © 1990.