Effect of an unforeseeable torrential downpour called guerrilla gouu on the growth of the rice plants.

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To clarify influence of the flood caused by the torrential rain on rice growth, we set 1, 2, 4 and 8 days submergence treatments in the major growth stages of rice. Effects of submergence on growth at the early growth stage (tillering stage) of rice became small with growth, and the negative effect on yield was small. On the other hand, submergence more than 2 days of the grain differentiate, the pollen forming and grain filling stages decreased the yield. Yield reduction was caused by the degeneration of the weak spikelet. In 8 days treatment of the late growth stage (panicle formation stage), high node tillers which does not appear in the normal cultivation conditions were observed. Apparent stem number greatly increased, but these stems did not grow up to panicles. Emergence of such tillers made center of gravity high, and changed the rice posture into the posture that was easy to lodge. The higher the flood water temperature, the damage caused by flood became remarkable.