CARBON ISOTOPIC COMPOSITION AND WATER-USE EFFICIENCY OF DEVONIAN AND EARLY CARBONIFEROUS LAND PLANTS

Research on modern plants imply that there is a negative linear relationship between water-use efficiency (WUE) and carbon isotopic composition value (usually in the form of δ¹³C values) of plants, so WUE differences of ancient plants may be reconstructed from δ¹³C data, through C-isotopic analysis of fossil plants. This project focuses on eight representative fossil plant genera of Devonian and Early Carboniferous time period (410- 320 Ma): Archaeopteris, Drepanophycus, Genselia, Leclercquia, Pertica, Psilophyton, Rhacophyton and Tetraxylopteris, which were collected from multiple localities mainly in the Appalachian Basin. These taxa show considerable variation in δ¹³C values, ranging from -20‰ to -30‰. At some localities, several different genera have been found from the same outcrop, which will allow evaluation of differences in WUE among different fossil plant taxa. Since environmental parameters would be the same or quite similar, differences of carbon isotopic composition would be caused by genome characteristics of different plant lineages, and so would the values of WUE. Several taxa are long-ranging, which will allow assessment of secular changes in WUE within individual lineages of early land plants. It is also possible to compare the same plant taxon from different geographic sites from the same geologic time period, which could supply ecological information from different habitats.