Molecular paleobotany ofNyssaendocarps

Abstract

SUMMARY Fruit endocarps of three recent Nyssa species from southern Georgia and endocarps of three Nyssa species from the late-Oligocene Brandon lignite, VT. are characterized and compared using pyrolysis gas chromatography–mass spectrometry (PYGCMS), pyrolysis-mass spectrometry (PYMS and desorption chemical ionization mass spectrometry DCIMS), and microscopic techniques. PYGCMS and PYMS demonstrated that during the lignitization process almost all of the carbohydrate material is removed from the endocarp fibre walls. Some hexose oligomer residues do survive lignitization as levoglucosan was observed in the PYGCMS trace of the lignitic endocarp N. fissilis and mass peaks indicative for anhydrohexose oligomers were observed in DCIMS spectra of N. fissilis and N. brandoniana. The PYGCMS data on the mixed guaiacyl–syringyl lignin in the recent and fossil endocarp wall have very similar pyrolysis product distributions. The abundance of phenolic pyrolysis products with aliphatic side chains suggest a different less oxygenated lignin in the endocarps compared to the Nyssa xylem cell walls. In spite of the significant chemical changes which occur during the early coalification process considerable microscopic detail can be preserved. Some fibre cell walls even retained an anisotropic character which may be caused by preserved crystalline cellulose. The effect of storage conditions on the chemistry of the paleobotanical samples was investigated by PYMS and multivariate analysis. Fossil endocarps stored in glycerin/ethanol experienced some extraction of a soluble lignin-derived fraction whereas water-stored endocarps did not. The residues of water glycerol/ethanol stored samples have similar polyphenolic polymers.