LIPID-PEROXIDATION CAUSED BY THE REDOX SYSTEM OF PLASMA-MEMBRANES FROM WHEAT ROOTS

The formation of malondialdehyde by plasma membranes purified by two-p hase partitioning from wheat (Triticum aestivum) roots was studied. MD A was produced when plasma membranes were incubated with NADH in the r eaction medium. SHAM stimulated MDA formation by plasma membrane, whic h was dependent on the plasma membrane protein and NADH. SOD, catalase , AsA and mannitol partially inhibited MDA generation. Water stress en hanced MDA formation by plasma membranes and the stimulating effect by SHAM was more pronounced. Further studies showed that the oxygen cons umption by plasma membranes was enhanced under water stress. EPR studi es indicated that the superoxide production of plasma membranes was st imulated by water stress. These results suggest that the generation of the oxygen radicals by the redox system of plasma membranes could be an important contribution to cellular radical concentration and could play a key role in the membrane damage through lipid peroxidation unde r water stress.