CARBON ISOTOPIC VARIABILITY IN MODERN AND ARCHAEOLOGICAL MAIZE

The carbon isotope compositions of maize seeds and seed components from three modern collections and archaeological sources were determined to examine biochemical variations in isotopic composition to establish the extent of variation in maize and maize types and to test whether archaeological samples were enriched in 13C relative to modern seeds. Endosperm was more positive (-10·8%) and the embryo more negative (-11·9%) than seed coats (-11·2%). This was consistent with more positive starch and more negative lipid and protein fractions in these compartments. Modern North American maize showed little variation (X¯ = −11·2 ± 0.03%) compared to the more diversified accessions from CIMMYT (X¯ = 11·0 ± 0·07%), or Goodman (X¯ = −10·7 ± 0·02). Although genetic variation is present, there were no significant differences among dent, flint, flour and sugar types. Archaeological maize does not change during carbonization, has a similar biochemical isotopic composition to modern maize and, when adjusted for anthropogenic alteration of atmospheric δ13CO2, has the same isotopic composition as modern maize. © 1993 Academic Press Limited.