ALTERATION OF PLASMA-MEMBRANE LIPIDS IN ALUMINUM-RESISTANT AND ALUMINUM-SENSITIVE WHEAT GENOTYPES IN RESPONSE TO ALUMINUM STRESS

We have studied the effect of aluminum (Al) on lipid composition of pl asma membranes from roots of an Al-resistant (PT741) and an Al-sensiti ve (Katepwa) cultivar of Triticum aestivum L. Several genotype-specifi c changes were observed in phospholipids and steryl lipids. While expo sure to 20 mu M AlCl3 for 3 days had no effect on total phospholipids in either genotype, the most abundant phospholipid, phosphatidylcholin e, increased significantly in the Al-resistant PT741 with correspondin g decreases in other phospholipids. In comparison, no change in phosph atidylcholine was observed in the Al-sensitive Katepwa. Aluminum also decreased steryl lipids (mainly free sterols) in PT741. Such changes w ere not observed in Katepwa. As a result of differential changes in li pid composition, the relative abundance of one lipid class to another changed. The ratio of steryl lipids to phospholipids decreased in PT74 1, with no change in Katepwa. While limited information on the relatio nship between membrane function and lipid composition makes it difficu lt to relate these changes to Al toxicity and resistance, changes obse rved only in the Al-resistant genotype could contribute to continued p lant growth in the face of Al stress.