Lipids in Cruciferae

Abstract

The effect of nitrogen, phosphorus and potassium nutrition on average seed weight, oil content and fatty acid composition of rape seed (Brassica napus) grown in soil-free culture has been studied. Nitrogen effected an increase in seed weight and a decrease in oil content, while the average amount of oil per seed remained constant. A small, but highly significant, decrease in palmitic and eicosenoic acid content, a significant decrease in oleic acid and a highly significant increase in erucic acid content were observed. This suggests that a decrease in the extent of elongation of oleic acid to erucic acid occurs in seeds developing on plants with sub-optimal levels of nitrogen nutrition. Phosphorus and potassium had very limited effects on fatty acid composition. Significant differences were found only in oleic acid content for phosphorus alone, the nitrogen-phosphorus interaction and the phosphorus-potassium interaction. The effect of various levels of sulfate at optimal levels for nitrogen, phosphorus and potassium, was studied in a separate experiment. Seed from sulfur-starved plants had decreased oil content; oleic acid percentages were increased and erucic acid percentages decreased. Excessive amounts of sulfate had no effect on fatty acid composition.