P. S. Sukhija

Lipid biosynthesis in developing kernels of almond (Prunus amygdalus)

Abstract An active process of oil filling which was initiated at 50 DAF (days after fertilization) reached a maximum level at 70 DAF, as revealed by [1-14C]acetate incorporation into lipids of developing almond kernels. A several-fold incorporation into total lipids was recorded with [1-14C]acetate, compared with [U-14C]glucose. Labelled glucose was incorporated mainly into the polar lipid fraction. Glycolipids were more effectively synthesized with [U-14C]glucose than with [1-14C]acetate with a partial loss of label in phosphatidylinositol (PI) and diphosphatidylglycerol (DPG) fractions. Addition of 0.5 mM glucose and glycerol, either singly or in combination, enhanced [1-14C]acetate incorporation into lipids at 50 DAF while at 70 DAF these compounds decreased the label. The possible role of cofactors like NADPH and/or ATP and glycerol originating from glucose has been discussed.

The influence of zinc and sulphur deficiency on oil-filling in peanut (Arachis hypogaea L.) kernels

In the developing peanut (Arachis hypogaea L.) kernels, the period between 15 and 35 days after podding (DAP) was identified as the active period of oil-filling. The period of active oil-filling was associated with a decrease in the starch, soluble sugars and proteins so as to make available the energy and carbon skeleton for the synthesis of oil. The oil content in the mature kernels decreased by 11, 12 and 25 per cent with Zn, S and Zn+S deficiency, respectively. In addition, proteins and starch content decreased significantly while that of soluble sugars increased slightly. The activity of malate dehydrogenase and glucose-6-phosphate dehydrogenase also decreased due to Zn as well as S deficiency. The deficiency treatments resulted in a decrease in phospholipids, free fatty acids and triacylglycerols in mature kernels. Further the proportion of 16∶0 and 18∶2 decreased while that of 18∶1 increased in developing kernels.

Polar Lipid Composition During Sunflower (Helianthus annuus) Seed Development

Summary The changes in the total lipids, polar lipids and their fatty acid composition at different stages of maturity of sunflower seed were studied. There was a rapid synthesis of oil between 10–30 days after fertilization and the synthesis reached its peak between 20–30 days after fertilization. The amount of polar lipids increased slowly as compared to non-polar lipids throughout the ripening period. Fatty acid composition of maturing seeds indicated a de novo synthesis of fatty acids along with the oil up to 30 days after fertilization and thereafter the desaturation process perhaps became active. Marked changes were observed in the fatty acid composition of individual polar lipid components during development. Among the phosphatides the fatty acid composition of PA and DPG resembled at all stages of development, thereby indicating some biosynthetic relationship between the two phosphatides.

Polar lipids of sun flower (Helianthus annuus L.) seeds

Qualitative and quantitative analysis of polar lipids in sun flower (Helianthus annuus L.) seed is reported in the present study. Ten classes of polar lipids i.e. phosphatidic acid, phosphatidyl inositol, phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl glycerol, diphosphatidyl glycerol, digalactosyl diglyceride, monogalactosyl diglyceride, esterified sterol glycoside and free fatty acids have been identified. Phosphatidyl choline and phosphatidyl inositol formed the major phosphatide fractions. Only four fatty acids i.e. palmitic, stearic, oleic and linoleic acids were present in measurable amounts in the total polar lipids. There was a great variation in the fatty acid composition in different classes of polar lipids. Arachidic acid was present in all the individual phosphatide fractions. Phosphatidyl glycerol was highly unsaturated followed by esterified sterolglycoside, phosphatidic acid, phosphatidyl ethanolamine + phosphatidyl glycerol, diphosphatidyl glycerol and monogalactosyl diglyceride.

Lipid composition of different zones of sunflower (Helianthus annuus) head during development

Summary The changes of the lipid composition of the seeds of three zones i. e. peripheral, middle and central, of maturing sunflower (Helianthus annuus) head have been studied. The peak period of lipid biosynthesis was between 10 and 20 days after fertilization. At 20 days the lipid content was higher in the seeds of peripheral zone than the seeds of either of the other two zones. Between 20 and 30 days there was no change in the lipid content of the peripheral seeds but an appreciable decrease in the lipid content of the middle and central zone seed took place. The pattern for acetate incorporation in various lipid classes was almost similar in the ripening seeds of all the three zones. Upto 20 days, the amount of oleic + linoleic acid was almost equal in the seeds of all the zones but at later stages this amount decreased in the seeds of the middle and central zone.

Lipid Composition and Fatty Acid Synthesis in the Blue Green Alga Anabaena doliolum

Summary The nature of polar lipids and fatty acid biosynthesis was studied in Anabaena doliolum, a blue green alga. The polar lipid fraction consisted of MGDG, DGDG, PG, SG, pigments and sulpholipids. In addition, one unidentified lipid was also present. CoA, ATP, G-6-P and F-1,6 di-P stimulated the fatty acid synthesis in the algal cells. Exogenous supply of ADP, Pi, NADH was without such a stimulatory effect. Light was an essential pre-requisite for fatty acid biosynthesis. Supply of citrate and isocitrate to the algal cells reduced the fatty acid and lipid biosynthesis.