Resumo

D`ANGELO, José Alejandro. Analysis by Fourier transform infrared spectroscopy of Johnstonia (Corystospermales, Corystospermaceae) cuticles and compressions from the Triassic of Cacheuta, Mendoza, Argentina. Ameghiniana [online]. 2006, vol.43, n.4, pp.669-685. ISSN 1851-8044.

Spectroscopic information (functional groups and semi-quantitative data) of corystosperm cuticles and compressions from the Triassic of Cacheuta, Mendoza, Argentina, is reported for the first time. Fossil leaves of Johnstonia spp. (Corystospermales, Corystospermaceae) were analyzed by Fourier transform infrared spectroscopy (FT-IR) in an attempt to identify spectroscopic patterns that would characterize these taxa. Infrared spectra obtained from cuticles and compressions of Johnstonia spp. showed a relatively rich aliphatic structure as well as hydroxyl, carbonyl and some other oxygen-containing functional groups. Semi-quantitative data derived from FT-IR spectra were statistically analyzed using one-way analysis of variance test (ANOVA). In the three taxa studied herein, one-way ANOVA revealed significant differences between cuticles and their corresponding compressions regarding the CH₂/CH₃ ratio (p < 0.05). Considering the FT-IR-derived ratios CH₂/CH₃, Al/Ox, Ox1/Ox2 and C-H/C=O, there were not significant differences (p > 0.05) between abaxial and adaxial surfaces in the cuticular samples of Johnstonia coriacea var. coriacea (Johnston) Walkom here studied. Infrared-derived ratios here considered (CH₂/CH₃, Al/Ox and Ar/Al) in compression samples did not differ significantly from one taxon to the other (p > 0.05). However, cuticular specimens of Johnstonia spp. showed statistical differences (p < 0.05) among the taxa studied, considering CH₂/CH₃, Ox1/Ox2 and C-H/C=O ratios. Although these results are suggestive of the likely application of FT-IR technique to the chemotaxonomic study of the Corystospermaceae, more data are needed before obtaining definitive conclusions.

Palavras-chave : Corystosperm cuticles; Johnstonia; FT-IR spectroscopy; Triassic; Cacheuta; Argentina.