Photosynthetic characteristics and resource utilization efficiency of maize (Zea mays L.) and millet (Setaria italica L.) in a semi-arid hilly loess region in China

Photosynthetic characteristics and resource utilization efficiency of maize (Zea mays L.) and millet (Setaria italica L.) are studied in a loess region of China. Limited sampling shows that maize has a higher light-saturated CO2 assimilation rate, apparent quantum yield and carboxylation efficiency than does millet in the middle (July) and late (September) growth stage. Compared with millet, maize has lower transpiration rate (Tr) and stomatal conductance (Gs) in July and higher Tr and Gs in September. This leads to higher leaf water use efficiency in maize in July, but it is lower than for millet in September. Mass-based leaf nitrogen concentrations (Nmass) of both crops are similar in both growth stages. Leaf mass per area (LMA) of maize is the same as of millet in July but lower in September. These results indicate differences in photosynthetic capacity and resource use efficiencies between these crops.