Ginkgo leaf cuticle chemistry across changing pCO2 regimes

Cuticles have been a key part of palaeobotanical research since the mid-19th Century. Recently, cuticular research has moved beyond morphological traits to incorporate the chemical signature of modern and fossil cuticles, with the aim of using this as a taxonomic and classification tool. For this approach to work, cuticle chemistry would have to maintain a strong taxonomic signal, with a limited input from the ambient environment in which the plant grew. Here, we use attenuated total reflectance Fourier Transform infrared (ATR-FTIR) spectroscopy to analyse leaf cuticles from Ginkgo biloba plants grown in experimentally enhanced CO2 conditions, to test for the impact of changing CO2 regimes on cuticle chemistry. We find limited evidence for an impact of CO2 on the chemical signature of Ginkgo cuticles, with more pronounced differences demonstrated between the abaxial (lower leaf surface) and adaxial (upper leaf surface) cuticles. These findings support the use of chemotaxonomy for plant cuticular remains across geological timescales, and the concomitant large-scale variations in CO2 concentrations