Effects of Physiological and Ontogenetical Ageing on Membrane Lipid Levels in Pea Leaves ( Pisum sativum)

Abstract

Summary The membrane lipid composition of leaves from pea was investigated during different stages of ageing. Total fatty acids, phospholipids, and free sterols were determined, on the one hand, in leaves of different maturity from plants with nine pairs of leaves, on the other hand, in newly unfolded leaves of plants of different ages. The leaves of different maturity were regarded as representing different stages of physiological ageing. The total fatty acids as well as the phospholipids decreased with increasing age. The level of free sterols was, however, constant. This implied a decrease in the mol ratio of free sterols/phospholipids from 0.16 to 0.33. The fatty acid composition of phosphatidylcholine changed to a lower unsaturation degree. The newly unfolded leaves of plants of different ages represented a variation in ontogenetical age with a constant level of physiological maturity. The total acyl lipids and the phospholipids of the newly unfolded leaves varied in a complex way during ontogenetical ageing and showed a min value at a plant size of seven leaves. The free sterols decreased with age. As a consequence the mol ratio of free sterols/phospholipids fluctuated between 0.1-0.2. Taken together the results indicate that the membrane lipid composition of pea leaves changes and reflects that form of ageing which prevails.