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

Changes in the acyl lipid composition of maturing embryos of oilseed rape (Brassica napus cv Shiralee) were quantified in plants cultivated in growth rooms. Rapid deposition of storage triacylglycerols began around 16 days after pollination (DAP) and continued till about 40 DAP after 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 diacylglycerol acyltransferase. Analysis of the fatty acid moieties of different lipid classes revealed that the pattern for triacylglycerols rapidly assumed that of the mature seed oil. The polar lipid fraction, in contrast to storage triacylglycerols, contained much less oleate (especially in immature seeds) reflecting the role of such lipids in membrane function. The acyl composition of the diacylglycerol fraction was intermediate between those of the triacylglycerol and the polar lipids except for mature seeds. Overall, for seeds raised in growth rooms, the final lipid composition and its detailed acyl quality agreed excellently with field-grown material.