Effect of nitrogen nutrition on photosynthesis and growth in C4Panicum species

Abstract

Abstract. The growth and photosynthetic responses to high and low N nutrition were measured in 2 NADP‐malic enzyme and 4 NAD‐malic enzyme C4 subtype Panicum species to evaluate whether differences in C4 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 C4 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.