IR SPECTROSCOPY REVEALS ECOPHYSIOLOGICAL STRATEGIES OF CORYSTOSPERMALES (TRIASSIC, ARGENTINA) AND MEDULLOSALES (CARBONIFEROUS, CANADA)

ZODROW, ERWIN L.; D`ANGELO J A

Otro; Reunión de comunicaciones de la Asociación Paleontológica Argentina; 2019

This study focuses on the relationships between chemical composition and ecophysiological characteristics of compression-preserved pinnules of (1) Triassic Corystospermales (Cacheuta, Argentina): Dicroidium odontopteroides and Johnstonia stelzneriana; and (2) Carboniferous Medullosales (Sydney, Canada): Linopteris obliqua and Lonchopteridium karvinensis. It is noted that the studied specimens were destroyed during the chemical analysis. Despite the different geographic and stratigraphic provenances, the constituting organic matter of all analyzed pinnules suffered minimal geothermal alterations (i.e., ?mild? fossilization conditions). This assures meaningful comparisons among their chemical compositions using infrared spectroscopy (IR) and principal component analysis. These IR data were used to calculate pinnules density (δ), leaf mass per area (LMA), leaf photosynthetic capacity (P m max), maximal Rubisco carboxylase activity (Vc max), leaf-nitrogen content (N), and leaf longevity (LL). Results indicate that, theoretically, D. odontopteroides and J. stelzneriana had the lowest values of δ, LMA, and LL, as well as the highest values of P m max, Vc max, and N. In contrast, Linopteris obliqua and Lonchopteridium karvinensis had the highest values of δ, LMA, and LL as well as the lowest values of P m max, Vc max, and N. These results suggest opposite trends in the use of resources among fossil taxa. D. odontopteroides and J. stelzneriana may have used an ?acquisitive? strategy resulting in small, fast-growing, tender, cheaply constructed, and short-expected leaf lifespan (and thus duration of photosynthetic income). Linopteris obliqua and Lonchopteridium karvinensis may have had a ?conservative? strategy, resulting in medium-sized, slow-growing, physically robust, costly, and long-lived pinnules.