Differences in cold lability of pyruvate, Pi dikinase among C4 species

Abstract

The cold lability of pyruvate, Pi dikinase in crude leaf extracts was studied in a number of C4 plants. The survey included C4 monocots and dicots and species representingthe three C4 subgroups: NADP-malic enzyme, NAD-malic enzyme, and PEP-carboxykinase types. In some species (e.g., Digitaria sanguinalis, Sorghum bicolor and Echinochloa crus-galli), the enzyme was very sensitive to cold treatment (half life of about 8 min at 0°C and 10 to 15 min at 10°C). In other species (Panicum miliaceum, Panicum maximum and Panicum texanum), the enzyme was very cold tolerant (retention of 60 to 85% activity after 60 min at 0°C and 90% activity after 60 min at 10°C). Among the plants examined, the most cold sensitive pyruvate,Pi dikinase was found among species of the NADP-malic enzyme subgroup.