Modification of the root plasma membrane lipid composition of cadmium-treated Pisum sativum

The effects of in vivo Cd treatments on pea root plasma membrane (PM) lipid composition were studied. In the long-term experiment, plants were supplied with Cd: moderate stress (10 mu m) or strong stress (50 mu M) for 10 d. growth of root and shoot was severely affected in 50 mu M Cd-treated plants, as evidenced by the approximately 7-fold reduction in their Relative Growth Increment (RGI). Treatment with Cd (10 mu M) resulted in changes to the lipid composition of the pea root PM, including increases in the degree of unsaturation of phospholipid-associated fatty acids and in the relative amount of stigmasterol (30-42%). This change was accompanied by a reduction in sitosterol content (26.8 to 17.4 mu g mg(-1) protein). However, the sterol composition was not altered in plants treated with 50 mu M Cd for 10 d. The content of phosphatidylethanolamine and phosphatidylcholine (major phospholipids present in pea root PM) decreased as Cd level increased, but the ratio between them remained unaffected. In the short-term experiment, plants exposed to Cd (50 mu M) accumulated less sitosterol (from 27.7 to 14.0 mu g g mg(-1) protein) over 72 h, but no significant effect on other measured lipids was observed. The physiological repercussions of changes in plasma membrane lipid composition, as a result of Cd exposure are discussed.