INFLUENCE OF EPTC (S-ETHYL-DIPROPYL-THIOCARBAMATE) ON THE COMPOSITIONOF SURFACE WAXES AND SPOROPOLLENIN STRUCTURE IN ZEA-MAYS

Thiocarbamate herbicides reduce the synthesis of very long chain fatty acids with C > 18. It was the aim of this study to reveal the involve ment of lipid metabolism and especially of the chain-elongating enzyme systems in sporopollenin biosynthesis by treatment of Zea mays plants with the thiocarbamate EPTC. The distribution patterns of lipid class es from external pollen and leaf waxes were comparatively analysed fro m treated plants and controls. On this basis it was elucidated that th e inhibitor is translocated in the plants, modifies the composition of lipid classes causing a shift to shorter chain lengths, and reaches t he sites of sporopollenin biosynthesis, these being the anther loculus and the pollen. FTIR spectroscopic analyses of isolated and purified exines revealed significant changes in the band pattern of sporopollen in from treated plants, thus demonstrating the influence of EPTC on th e chemical composition of sporopollenin by interaction with chain-elon gating enzyme systems. The deviations from control spectra caused by E PTC are interpreted as an enhanced degree of polymer cross-linking by ether and/or ester bonds in order to compensate the reduced chain leng ths of the aliphatic compounds that participate in the sporopollenin s tructure. This biochemical approach indicates that lipid metabolism an d chain-elongating enzyme systems are involved in the synthesis of thi s remarkable biopolymer.