Characterizing Modern and Fossil Gymnosperm Exudates Using Micro-Fourier Transform Infrared Spectroscopy

Abstract

Infrared absorption spectra of exudates from 65 species of gymnosperms were measured using microFourier transform infrared (FTIR) spectroscopy. On the basis of the infrared spectra, three compositionally distinct groups of exudates can be distinguished: resins, volatile-rich resins, and gums. Resins and volatile-rich resins are mainly composed of terpenoids, whereas gums are polysaccharides. Resins and volatile-rich resins are restricted to conifers (Pinophyta). Gums, on the other hand, are produced by some conifer families including Araucariaceae and Podocarpaceae; nonconifer gymnosperms including Ginkgo (Ginkgophyta), cycads (Cycadophyta), and Welwitschia (Gnetophyta); and angiosperms. Using spectral band ratios, conifer resins can be subdivided quantitatively into two distinct resin types that reflect compositional differences in their terpenoid constituents and broadly parallel different conifer families. The first type of resin (pinaceous resin) is produced by members of Pinaceae and consists mainly of diterpenes that are based on abietane/ pimarane skeletal structures. The second type (cupressaceous resin) is associated with members of the Cupressaceae, Sciadopityaceae, Araucariaceae, and Podocarpaceae and consists mainly of diterpenes that are based on the labdanoid structures. Variability within the resin spectra correlates with the number of free hydroxyl groups, and it can be used to assess the degree of resin polymerization. Volatile-rich resins are found exclusively within Pinaceae, reflecting a generally higher abundance of volatile mono-and sesquiterpenoids in resins of this family. The results of the FTIR spectroscopy have direct implications for the assessment of the fossil potential and the chemotaxonomic interpretation of modern and fossil gymnosperm exudates.

Chemical Characterization and Botanical Origin of French Ambers

“…These exocyclic methylene groups are characteristic of some acids (communic and ozic), thus supporting the presence of the labdatriene polymeric structures in the ambers studied. 21 Finally, when compared to the spectra of recent resins, 13 all Cretaceous ambers present affinities with the conifer families Cupressaceae and Araucariaceae, especially in their fingerprint area. Pinaceae, another important family of resin-producing conifers, could be excluded from the possible plant sources, due both to the absence of the 887 cm −1 peak in recent pinaceous resins and to the relative intensities of other peaks.…”

“…30 A previous chemical analysis of this amber was performed using FTIR, NMR, and Py-GC-MS, but without a detailed description of the labdanoid molecules. 30 Thus, we performed a new investigation by FTIR, solid-state 13 C NMR, and thermochemolysis−GC-MS, with the same protocol used for the French ambers. The resulting spectra (Figures S14, S15, Supporting Information) do not differ from those published previously, 30 but more compounds were identified (Table S3, Supporting Information).…”

Phylogeny of cultivated and wild wheat species using ATR–FTIR spectroscopy

“…Roots of Pea and Oat plants were successfully discriminated by FTIR-ATR spectroscopy [18]. A total of 65 gymnosperm plant exudates were characterized and compared by micro-FTIR spectroscopy [19]. The results were postulated to have direct implications for the assessment of fossil potential and the chemotaxonomic interpretation of modern and fossil gymnosperm exudates.…”

Amber from México: Coahuilite, Simojovelite and Bacalite

“…The IR spectrum shows particular fingerprints regions related to identity and botanical affinities of both amber and recent resins. This allows to elucidate the provenance, botanical affinities and mineral species of ambers and others fossil resins [1,9,[13][14]. The assignments of infrared spectral features in fossil and recent resins have been published in numerous works [11][12]14].…”

“…This allows to elucidate the provenance, botanical affinities and mineral species of ambers and others fossil resins [1,9,[13][14]. The assignments of infrared spectral features in fossil and recent resins have been published in numerous works [11][12]14]. In the present study, amber samples recently collected from the geological deposits of Chiapas, Coahuila and Baja California, México, have been characterized using Synchrotron-based Infrared (FTIR) microspectroscopy, with direct implications in fossil resin nomenclature.…”