Changes in Fatty Acid Composition of Phospholipids from Different Ages of Potato Seed-tubers During Sprouting

The relative growth rate of plants from 7-month-old potato seed-tuberswas significantly greater (37%) than that from 19-month-oldseed-tubers. To determine if loss in seed-tuber phospholipidcontent, and thus membrane integrity, is associated with age-reducedvigour, changes in fatty acyl composition of free fatty acid(FA) and phospholipid fractions were characterized in both seed-tuberages over a 19-d interval of plant establishment. The concentration(nmol g d. wt^–1) of saturated and unsaturated FA withinthe phosphatidylcholine (PC) and phosphatidylethanolamine (PE)pools decreased an average of 27-fold over the initial 7 d ofestablishment. This decline was followed by a 19-fold (on average)increase to day 19. The change with time in saturated and unsaturatedFA concentration within the free FA pool was quadratic, butwas opposite to that displayed by the two phospholipid pools.The close correlation in fatty acyl content between the phospholipidand free FA fractions suggested high phospholipase activityduring early plant establishment. The double-bond index (DBI)of all three lipid fractions decreased from day 0 to 7 and thenincreased to day 19. More importantly, in older seed-tubers,the minima in phospholipid DBI and content occurred significantlyearlier (on a plant developmental scale) than in younger seed-tubers.A premature decrease in DBI is indicative of loss of membraneintegrity in potato, and undoubtedly has implications for efficiencyof substrate mobilization and energy metabolism during plantestablishment. Potatoes (Solanum tuberosum L.), seed-tuber age, lipids, plant growth potential