Compositional changes and biosynthesis of lipids in the developing kernels of almond (<i>Prunus amygdalus</i> batsch)

Abstract Fruit and kernel weights of developing almond kernels increased with age. The kernel contents had a translucent and jelly‐like appearance in the initial developmental stages, but solidified prior to the accumulation of dry matter, mainly oil, from 50 days after fertilisation (DAF). During kernel development the oil content displayed a double sigmoid pattern. Oleic and linoleic acids accumulated to similar levels, but the linolenic acid content decreased during development. Oil‐filling ([1‐ 14 C]acetate incorporation) commenced at 50 DAF, and reached a maximum level at 70 DAF. The total polar lipid content was highest at 10 DAF, as determined by radioactive labelling, but from 30 DAF onwards a de‐novo synthesis was noted. Diphosphatidyl glycerol (Cardiolipin) acted as a temporary reservoir for the synthesis of phospholipids from 70 DAF, and thereafter the synthesis of phosphatidyl choline was enhanced. In the initial stages, the rate of synthesis of monogalactosyl diglycerides was greater than that of digalactosyl diglycerides, and a de‐novo synthesis of both was observed from 30 DAF. The synthesis of triacylglycerols corresponded well with the pattern of oil‐filling. The level of 14 C radioactivity recorded in sterol esters was greater at the initial stages, but declined from 50 DAF, possibly because of the effect of dilution, as envisaged in the case of the triacylglycerols.