Simulated diagenesis of plant cuticles — implications for organic fossilisation

Abstract

The possible origin of the characteristic compositions of pyrolysates of organic fossil leaf cuticles has been investigated by heat treatment of cuticles of recent Kalanchoe grandiflora followed by flash pyrolysis–gas chromatography. Dewaxed cuticles, whether heat-treated or not, yield mainly cyclic compounds from adventitious cell-wall material together with cutin monomers. The pyrolysate of waxy cuticle includes the same compounds but is dominated by wax components which are simply desorbed unchanged under the conditions of pyrolysis. However prior heat treatment of waxy cuticle transforms the pyrolysate so that its chromatogram shows a prominent series of alkene–alkane peaks from C 8 to C 34, typical of fossil leaf cuticles. It is concluded that leaf waxes, instead of or in addition to cutan, are a principal source of the aliphatic constituents of organic fossil leaf cuticles.