Changes in molecular species of triacylglycerols in developing cotton seeds under salt stress

Cotton plants (Gossypium hirsutum L. cv. S4) were grown and irrigated with increasing salt concentrations: 0, 50, 100 and 150 mM NaCl. Lipids from developing seeds, at stages of 3, 4, 5 and 6 weeks after anthesis, were analysed. High salt dose (150 mM NaCl) affected triacylglycerol levels drastically at the end of ripening. HPLC analysis of triacylglycerols in control seeds showed ten molecular species. Palmitodilinolein (PLL) is the major fraction, representing about 25% of total triacylglycerols. The levels of trilinolein (LLL), palmitolinoleo-olein (PLO) and oleodilinolein (OLL) molecules varied between 13 and 16% of the total. The other molecular species: triolein (OOO), dioleopalmitin (POO) and dipalmito-olein (POP) are minor and do not exceed 5%. Moreover, the composition of triacylglycerol molecular species was almost constant during developing stages of control seeds. However, amounts of triacylglycerol species LLL, OLL and palmitodilinolein (PLL), as expressed on a dry-matter basis (mg/g), decreased severely under the highest NaCl concentration, while contents of triacylglycerol species OOO, POO, POP were unchanged. These findings confirm our previous results, which indicated that the amount of linoleic acid in cotton seeds was reduced by salt stress and that the amount of oleic acid remained unchanged.