The synthesis of triglyceride and other non-polar acyl lipids by protoplasts and chloroplasts from barley leaf : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science with Honours in Biochemistry at Massey University
Protoplasts, isolated from barley leaf, were incubated with H¹⁴CO₃ and (1-¹⁴C) acetate. The radioactivity was found incorporated into the lipids sulpholipid, phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl glycerol, and monogalactosyl diglyceride as identified by thin layer chromatography. Large quantities were found in an unidentified region referred to in this thesis as USF (Unknowns near the solvent front) . ThisUSF was much less polar than the phospholipids and galactolipids and ran in the same region as plant pigments. USF, by using TLC with several solvent systems, was identified as consisting of acyl lipids; the major proportion was triglyceride (approximately 55%) with diglyceride, free fatty acid and monoglyceride also present. The radioactivity in the triglyceride was found, by GLC of methylated esters, to be contained in the fatty acids; mainly in linoleate (18:2)and palmitate (16:0) and in lesser concentrations in stearate (18:0) and oleate (18:1). Endogenous levels of triglyceride were found to be very low - only 14.8 nmoles /g of fresh tissue. The results of experiments with sections of tissue of different maturity suggested that the high level of incorporation into acyl lipids was related to tissue immaturity. Chloroplasts were isolated by a traditional blending method and by bursting prepared protoplasts. The latter technique produced chloroplasts of a higher quality. Examination of the incubation products when chloroplasts were incubated with (1-¹⁴C) acetate showed once more the appearance of acyl lipids. Triglyceride made up 35% of the USF from chloroplasts incubations. The label accumulated mainly in palmitate (16:0) on the triglyceride. These results suggest that at least part of the triglyceride synthesis in the plant cell is occurring within the chloroplast, contrary to the findings represented in the literature.