• C4 photosynthesis;
  • chilling;
  • sugarcane

FBPase, fructose-1,6-bisphosphatase NADP-MDH, NADP-malate dehydrogenase NADP-ME, NADP-malic enzyme OAA, oxaloacetic acid PEP, phosphoenolpyruvate PEPcase, phosphoenolpyruvate carboxylase PPDK, pyruvate orthophosphate dikinase Rubisco, ribulose-1,5-bisphosphate carboxylase/oxygenase The aim of this study was to investigate the mechanism of photosynthetic changes in sugarcane leaves in response to chilling temperature by using three species (Saccharum sinense R. cv. Yomitanzan, Saccharum sp. cv. NiF4 and Saccharum officinarum L. cv. Badira) differing in origin and cold sensitivity. Yomitanzan is native to subtropical areas, Badira is native to tropical areas and NiF4 is a hybrid species containing genes of both tropical and subtropical species. At exposure to chilling temperature (10 °C), the photosynthetic rate in the leaves at either 10 °C or 30 °C showed a greater decrease in Badira than in NiF4 and Yomitanzan. After 28 h exposure of plants to the chilling temperature, the extractable activities of pyruvate, orthophosphate dikinase (PPDK) and NADP-malate dehydrogenase (NADP-MDH) increased or were relatively stable in the leaves of NiF4 and Yomitanzan, but decreased substantially in Badira. Correspondingly, there was a substantial accumulation of aspartate, and the level of alanine increased in Badira leaves during the chilling treatment. It is suggested that NADP-MDH and PPDK are key enzymes which may determine the cold sensitivity in photosynthesis of sugarcane.