Abstract Detail

Novel Approaches to Plant Evolution from Paleontological, Physiological, and Developmental Perspectives

Gulbranson, Erik L [1], Harper, Carla J [2].

Tree physiology and nutrient acquisition in deep time: an isotopic perspective to supplement paleobotanical inferences.

Stable isotope investigations on fossil plants have largely focused on carbon isotope geochemistry and the relationship to paleoclimate and ecology. In contrast, studies of (paleo) plant physiology and/or adaptations of plants are based primarily on anatomical and morphological data. This talk explores new methods and applications for stable isotope analysis of ancient plants using fossil wood. We utilize carbon (C) and nitrogen (N) isotope analyses to bridge the morphologic and geochemical analyses of fossil wood for reconstructing the physiology and possible nutrient uptake strategies by plants in paleoenvironments. The broader significance of this objective is to develop new methodologies to study the evolution and ecologic implications of plant adaptations to stress and disturbance(s), and to provide insight into the evolution of plant-microbe symbioses, which are vital to modern and ancient terrestrial ecosystems. The first case study discussed is the use of C isotope geochemistry of fossil wood via studies of plant metabolism in modern trees. Position-specific isotope analysis of glucose is used as a tracer to document how the subtle difference in carbohydrate metabolism in evergreen and deciduous trees imprints a distinct C isotopic pattern in annual growth rings. Applications of this technique to the fossil record will highlight the unique C isotope trends of tropical and polar trees, demonstrating that leaf longevity can be reconstructed from the fossil record and that latitudinal distinctions are evident in these specific plant-environment adaptations. Nitrogen isotope geochemistry of modern and fossil wood is difficult to measure due to the low abundance of N. Moreover, interpretations of N isotopes in extant ecosystems are complex due to the numerous pathways of N transfer, conversion of organic N to mineralized N, rates of N metabolism, intra-plant N isotope fractionation, myriad N isotope fractionation factors for soil microorganisms, etc. Here, we elucidate these complexities by first focusing on screening wood for the presence and form of N in wood specimens to establish their viability for N isotope analysis. Second, we present a study of N isotopes in Oligocene tropical trees in a Fabaceae-dominated forest to illustrate that N-fixing symbioses can be adequately interpreted in the fossil record via N isotope analysis. Third, we preview new methods to further study the nature of mycorrhizal symbioses in the fossil record.

1 - University of Wisconsin-Milwaukee, Geosciences, 3209 N. Maryland Ave, Lapham Hall 366, Dept of Geosciences, Milwaukee, WI, 53211, USA
2 - Ludwig-Maximilians-Universität, Staatssammlung für Geo- und Umweltwissenschaften, Paläontologie und Geobiologie, Richard-Wagner-Straße 10, Munich, 80333, Germany

Keywords:
fossil wood
carbon isotope
nitrogen assimilation
mycorrhizae
geochemistry
paleoecology.

Presentation Type: Symposium Presentation
Session: SY11, Novel approaches to plant evolution from paleontological, physiological, and developmental perspectives
Location: 101/Savannah International Trade and Convention Center
Date: Wednesday, August 3rd, 2016
Time: 2:15 PM
Number: SY11003
Abstract ID:112
Candidate for Awards:None