Carbon and nitrogen isotopic variability in foxtail millet ( <scp> <i>Setaria italica</i> </scp> ) with watering regime

Abstract

The carbon isotope ratios of Setaria italica are strongly correlated with water availability. However, the correlation is the opposite to that seen in studies of C₃ plants. The difference in isotopic ratio due to watering regime is comparable with that seen between different accessions; thus distinguishing between changing varieties of Setaria italica and changing climate is problematic. In terms of grain nitrogen isotope ratios, the highest δ¹⁵ N values were not associated with the lowest watering regime. Again, δ¹⁵ N variation is comparable with that which would be expected from an aridity effect or a manuring effect, and thus distinguishing between these factors is probably problematic.