Abstract
Deep-flood irrigation (DFI) is a method used to suppress the occurrence of chalky grains, which is becoming a serious problem due to global warming. The mechanism of reducing chalky grains by DFI was analyzed with regard to the source ability of stems and leaves that supply carbohydrate to the grains because shortage of carbohydrate flow into the endosperm is considered to be the main cause of chalky grains. DFI increased the amount of nonstructural carbohydrate (NSC) reserved in stems and leaf sheaths at the full heading stage. This result suggests that DFI increased the translocation of carbohydrate reserved in stem and leaves before heading. In addition, DFI increased the amount of nitrogen in leaf blades at the full heading stage as well as leaf area at the ripening stage, which suggests that DFI promotes photosynthesis in the ripening process. In conclusion, DFI increases both the amount of carbohydrate reserved before heading and photosynthetic ability after heading, consequently decreasing the occurrence of chalky grains.
