First record of foliar cuticle of Zea mays L. (maize, Luracatao, Salta, Argentina, c. 1000?1470 a d). Spectrochemical and microscopical analyses

CAMÍ, G; D`ANGELO J A

Simposio; XVII Simposio Argentino de Paleobotánica y Palinología; 2018

Foliar cuticle of Zea mays L. (maize) recovered from a pre-Hispanic, funerary archaeological site atLuracatao, Salta, Argentina is reported for the first time. The cuticle is part of a number ofarchaeological features consisting of ritual offerings excavated from earthen platform mounds (SantaMaria culture, c. 1000?1470 A D). Sample consists of a single, millimeter-sized, cuticular fragment of acarbonized maize blade recovered from the carbonaceous, powder material surrounding abundantmaize grains and cobs and a variety of burnt plant parts. Cuticle was analyzed by scanning electronmicroscopy (SEM) combined with Fourier transform infrared spectroscopy (FTIR). SEM shows welldevelopedcostal (vein) and intercostal zones. Epidermal cells overlying the veins are elongate, sinuous,rectangular, and regularly arranged with their long axes parallel to the vein. Vein cells are frequentlyinterspersed with short silica cells (phytoliths) and likely cork cells. Phytoliths shapes range fromdumbbells to saddles, and crosses. Intercostal cells are elongate, sinuous, rectangular to polygonal orbroadly rectangular. Stomata are rare and confined to the intercostal zones, where abundant phytolithsand excellently preserved microhairs are present. FTIR spectra indicate that maize leaf cuticle preserveshigh contents of aromatic compounds while the contribution of aliphatic and oxygen-bearing structuresis considerably low. The presence of phytoliths is confirmed by high-intensity IR peaks of Si-O bondingfrom opal-A. The excellent preservation of this unprecedented foliar cuticle of sub-fossil (500?1000years old) maize permitted to present the morphological-chemical changes of organic matter resultingfrom likely funerary (burning) rituals and diagenetic alterations.