GLYCEROLIPID AND FATTY-ACID CHANGES IN EASTERN WHITE-PINE CHLOROPLAST LAMELLAE DURING THE ONSET OF WINTER

Chloroplast lamellae of eastern white pine (P. strobus L.) were analyzed to determine changes in total glycerolipids, component glycerolipids and glycerolipid fatty acids during the onset of winter hardiness. Samples were collected in Sept., Nov. and Dec. when the average daily temperature varied between 23 and -10.degree. C. Before Nov. 2, phospholipids decreased 40-85%, glycolipids only 30%. Analysis of individual glycerolipids showed that glycerolipids containing 18:3 fatty acid were retained at the expense of glycerolipids esterified with saturated (16:0 and 18:0) and monounsaturated (18:1) fatty acids. Between mid-Nov. and Dec., the total quantity of lamellar glycerolipids recovered to the Sept. level. Increases in digalactosyl diglyceride and in 18:3 characterized the recovery period. High lamellar unsaturation achieved by mid-Nov. appeared to be maintained during recovery through preferential incorporation of glycerolipids containing 18:3 (monogalactosyl diglyceride, digalactosyl diglyceride, phosphatidylglycerol, and phosphatidylcholine). Eastern white pine chloroplasts apparently maintain lamellar viscosity by increasing lamellar unsaturation and tolerate freeze desiccation by increasing the interfacial water-binding capacity of the lamellae.