Lipids and NADPH-dependent superoxide production in plasma membrane vesicles from roots of wheat grown under copper deficiency or excess

The effects of in vivo copper on the lipid composition of root plasma membr ane and the activities of membrane-bound enzymes, such as NADPH-dependent o xidases and lipoxygenase, were studied. Plants were grown in hydroponic cul ture for 11 d without Cu supply or in the presence of 50 muM Cu. Control pl ants were supplied with 0.3 muM Cu. Growth of roots was severely affected i n the 50 muM Cu-grown plants, whereas roots grown in Cu-deficient solution did not show any difference in comparison with the control. The 50 muM Cu c oncentration caused an increase in the leakage of K+ ions as well, Excess m etal supply resulted in a decrease in the total lipid content of plasma mem brane, a higher phospholipid amount and a reduction of steryl lipids (free sterols, steryl glycosides and acylated steryl glycosides), Cu depletion in the growth solution had only a slight effect on the plasma membrane lipid composition, In comparison with the control, only the excess of Cu caused a decrease in the lipid to protein ratio as well as a change in the phosphol ipid composition, with a lower phosphatidylcholine to phosphatidylethanolam ine ratio. The degree of unsaturation of root plasma membranes decreased fo llowing the 0 Cu treatment and even more after the 50 muM Cu supply, Plasma membranes of wheat grown under metal deficiency and excess showed increase d NADPH-dependent superoxide-producing oxidase activities, whereas membrane -bound lipoxygenase was not increased or activated due to Cu treatments, Th e consequences of changes in plasma membrane lipid composition and activate d oxygen production as a result of Cu treatments are discussed.