Aspects of Sporopollenin Biosynthesis: Phenols as Integrated Compounds of the Biopolymer

The structure and biosynthetic pathway of sporopollenin are largely unknown. In 1971, Brooks and Shaw have postulated that sporopollenin is generated from carote­ noids and carotenoid esters. This assumption is based on comparartive studies on the naturally occuring sporopollenin and polymers which were synthesized from carotenoids. Both the natural and the synthetic macromolecules exhibit a high level of resistance to acetolysis; both show similar IR spectra and have similar elemental composition. As far as higher plants are concerned, this hypothesis has not yet been confirmed by tracer experiments. However these are exactly the kind of experiments which are needed to establish whether isoprenoid metabolism is involved in sporopollenin biosynthesis and whether further, or completely different, metabolic pathways participate. To remove the confusion about the nature of this important plant material, the following experiments were performed: ~ Highly purified sporopollenin was degraded in order to analyse the resulting low molecular degradation products. These investigations were focussed on the appearance of phenols as degradation products. These results obtained from naturally occuring sporopollenin were compared with those from "synthetic sporopollenin". 2. On the basis of an optimized technique extensive tracer experiments were carried out with a variety of added precursors.