Effect of nitrogen nutrition on photosynthesis and growth in C₄Panicum species

The growth and photosynthetic responses to high and low N nutrition were measured in 2 NADP‐malic enzyme and 4 NAD‐malic enzyme C 4 subtype Panicum species to evaluate whether differences in C 4 photosynthetic biochemistry result in differences in the N requirement for growth. All species had lower biomass production, photosynthesis rates, and shoot N concentrations at low N, and no consistent differences between the C 4 subtypes were apparent. The assimilation rates (biomass accumulated over the period of growth) for the NADP‐malic enzyme species were higher than the NAD‐malic enzyme species at high N but not at low N. When assimilation rates were evaluated on a shoot N basis a higher N‐use‐efficiency was found for the NADP‐malic enzyme species at high N. Thus the NADP‐malic enzyme Panicum species had a greater amount of growth for a given shoot N concentration, but only above a certain level of shoot N concentrations.