Cutin of Johnstonia coriacea (Corystospermaceae, Upper Triassic, Cacheuta, Argentina)

D`ANGELO J A

Mendoza

Jornada; XXXVI Jornadas Argentinas de Botánica junto con la XXVIII Reunión Anual de la Sociedad de Botánica de Chile y la II Reunión Científica de la Asociación Micológica Carlos Spegazzini; 2017

Cutin, one of the major constituents of plant cuticles, is a waxy polymer consisting of longchainedhydroxy fatty acids and derivatives, which are cross-linked via ester bonds. Here, I reportthe presence of cutin polymer recovered from fossil remains (coalified compressions) ofJohnstonia coriacea (Johnston, 1887) Walkom, 1925 (Corystospermales, Corystospermaceae)from the Upper Triassic of Cacheuta (Argentina). Time-controlled Schulze?s oxidation reactionswere used to obtain both cuticle and cutin polymer. Variations of chemical structure as a functionof cutin concentration were monitored via semi-quantitative Fourier transform infrared (FTIR)spectrometry. Distinct features of the cutin spectrum include intense peaks of ester carbonyl(C=O), centered at 1728 cm-1, and aromatic C=C absorption bands at 1640 cm-1. SemiquantitativeFTIR-derived data indicated that cutin is characterized and differentiated from thecorresponding J. coriacea cuticle by the comparatively lower values of CHal/C=O, CH2/CH3,C=C contribution, CHal/Ox as well as the higher values of C=C contribution, and C=O/C=C.Some of the cutin data compare with available semi-quantitative FTIR data from modern L.esculentum cutin. This is particularly the case of the CHal/C=O values recorded i.e., J. coriacea =0.8 (L. esculentum = 0.9). The latter indicates that both fossil and extant taxa have a similar crosslinking degree of the cutin structure.