Abstract
The concentration of fluorine to the public water bodies permitted by water pollution law is 15 mg L-1. The growth of rice plants was severely depressed by fluorine added to the culture solution at 5-10 ppm. The purpose of this investigation was to make clear the limit value of fluorine on the growth of rice plants and to clarify the absorbing mechanism by the roots of rice plants. The effect of the fluorine(HF)added to the culture solution at 0, 2, 4 and 6 ppm on the growth of Oryza sativa L.cv.Koshihikari was investigated. The increase in the leaf length and the number of stems per hill was depressed by the fluorine added. Especially, the number of stems per hill was obviously decreased by increasing the concentrations of HF. The number of ears and unhulled rice per hill were decreased by the lower concentrations of HF. It was clarified that the dry weights of unhulled rice, leaves, and roots were markedly decreased by fluorine at the lower concentrations. The fluorine content in leaves increased by increasing the concentration of HF and prolonging the growth period. It was shown that the fluorine absorbed through the roots was accumulated in brown rice, leaves, stems and roots.
