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Field-grown Miscanthus × giganteus maintains high photosynthetic quantum yields and biomass productivity in cool temperate climates. It is related to maize (Zea mays) and uses the same NADP-malic enzyme C₄ pathway. This study tests the hypothesis that M. × giganteus, in contrast to maize, forms photosynthetically competent leaves at low temperatures with altered amounts of pyruvate orthophosphate dikinase (PPDK) and Rubisco or altered properties of PPDK. Both species were grown at 25°C/20°C or 14°C/11°C (day/night), and leaf photosynthesis was measured from 5°C to 38°C. Protein and steady-state transcript levels for Rubisco, PPDK, and phosphoenolpyruvate carboxylase were assessed and the sequence of C₄-PPDK from M. × giganteus was compared with other C₄ species. Low temperature growth had no effect on photosynthesis in M. × giganteus, but decreased rates by 80% at all …