CADMIUM-INDUCED AND COPPER-INDUCED CHANGES IN TOMATO MEMBRANE-LIPIDS

Cadmium and copper uptake and distribution, as well as their effects o n growth and lipid composition were investigated in 17-day-old tomato seedlings (Lycopersicon esculentum Mill. cv. 63/5 Fl) grown in culture solution supplied with two concentrations of Cd or Cu (0, 5 and 50 mu M). The accumulation of Cd and Cu increased with external metal conce ntrations, and was considerably higher in roots than in primary leaves . Biomass production of the growing roots and primary leaves was stron gly depressed at high metal levels. Also, significant decreases in the content of lipid classes and changes of fatty acid composition were r ecorded in heavy metal-stressed plants in comparison with controls. Gl ycolipid contents were decreased more in leaves than in roots by Cd-tr eatment, but copper decreased both to similar extents in both organs. Likewise, both metals reduced the phospholipid and neutral lipid conte nts more in roots than in leaves. In almost all lipid classes the prop ortion of palmitic acid (16:0) increased: and that of linoleic (18:2) or linolenic (18:3) acid decreased, suggesting that heavy metal treatm ent induced an alteration in the fatty acid desaturation processes. Fu rthermore, the accumulation of palmitate (16:0) rather than stearate ( 18:0) indicated an alteration in the ratio of products from the fatty acid synthase. Copper was found to be the most unfavourable for plant growth and lipid metabolism. The possible mechanisms by which heavy me tals, especially Cu, induce a strong lipid shift are discussed. (C) 19 97 Elsevier Science Ltd. All rights reserved.