CHANGES IN THE LIPID-CONTENT OF DEVELOPING SEEDS OF BRASSICA-NAPUS

Changes in the acyl lipid composition of maturing embryos of oilseed r ape (Brassica napus cv Shiralee) were quantified in plants cultivated in growth rooms. Rapid deposition of storage triacylglycerols began ar ound 16 days after pollination (DAP) and continued till about 40 DAP a fter which seed desiccation proceeded. Diacylglycerols were present in significant amounts during the rapid phase of oil accumulation, which may suggest a rate limitation in carbon flux at the level of diacylgl ycerol acyltransferase. Analysis of the fatty acid moieties of differe nt lipid classes revealed that the pattern for triacylglycerols rapidl y assumed that of the mature seed oil. The polar lipid fraction, in co ntrast to storage triacylglycerols, contained much less oleate (especi ally in immature seeds) reflecting the role of such lipids in membrane function. The acyl composition of the diacylglycerol fraction was int ermediate between those of the triacylglycerol and the polar lipids ex cept for mature seeds. Overall, for seeds raised in growth rooms, the final lipid composition and its detailed acyl quality agreed excellent ly with field-grown material.