Abstract
The reduction of lodging resistance of rice plant due to submersion was analyzed. The results are summarized as follows. 1. The sheath of leaf embracing the culm prevents the plant from lodging. 2. The longer the length of internode at the basal portion is, the weaker the internode becomes. 3. The strength of each portion of internode with leaf sheath is larger at its lower part than the upper one due to the embracement of leaf sheath, but the strength of internode without leaf sheath is weaker at the lower part because of its low density of structure. 4. Submersion deteriorates the lodging resistance of rice plant by the following reasons. (1) The strength of leaf sheath is weakened. (2) The folding tension of leaf sheath in culm decreases due to swelling. (3) The strength of basal internode decreases due to abnormal elongation. (4) The flexural rigidity is weakened due to the decrease of dry matter. (5) The thickness of culm wall is diminished. (6) The tissue in leaf sheath is degenerated and the formation of silica cell is inhibited.
