A MOLECULAR APPROACH TO PALEO-PLANT ECOPHYSIOLOGY: DECIDUOUS CONIFERS FROM EARLY TERTIARY ACTIC DEPOSITS AS EXAMPLES

Ancient biomolecules and their isotope signatures preserved in identifiable plant fossils carry valuable evidence of the environmental conditions under which these biomolecules were synthesized and registered in the geological record. Recent applications of biochemical and molecular isotope technology allows extraction, characterization, and isotopic measurement of a variety of in situ biomolecules from fossil plant compressions. The preservation of structural biopolymers offers the molecular basis for the retention of morphological characters and provides insights into the intricacy of ancient forest productivity, litter decomposition, and long term preservation. Molecular isotope signatures can record unique information regarding plant adaptations to light, environmental water, and atmospheric conditions. The applications of these techniques are illustrated in a study of fossil deciduous conifers from late Paleocene-middle Eocene floodplain deposits at high latitudes of the Canadian Arctic. Labile biomolecules such as polysaccharides and cutin acids detected in the three dimensionally preserved plant tissues indicate taxon-specific low rates of litter decomposition under the Tertiary global warming climate. Isotope signals recovered from leaf tissues revealed evidence for plant adaptations to the challenging condition of photosynthesis and evapotranspiration under the unique polar light regime at the Tertiary high latitudes.