Effect of Atmospheric Fluoride on Plants

In this report, gladiolus (Gladiolus gandavensis), mandarin (Citrus Unshiu), taro (Colocasia antiquorum), Japan-ceder (Cryptomeria japonica) and rice (Oryza sativa) were used as plant indicators of air-pollution by fluoride. The sensitivity of these plants against atmospheric fluoride was found to be taro>gladiolus>Japan-ceder>mandarin. On the other hand, the pool size of fluorine accumulation in plant leaves was suggested to be Japan-ceder>mandarin>gladiolus>taro. The calcium contents in the leaves of mandarin and gladiolus were 4.16% and 1.04% as average, respectively. The ratio of Ca/Si in the leaves of mandarin and gladiolus was 32.7 and 4.38 as average, respectively. The contents of calcium and silica in the leaves in plants were suggested to be concerned with the sensitivity of plants against atmospheric fluoride. Accumulation of fluorine in unhulled rice was associated with fluorine content in the rice bran, but was not associated with that in the polished rice. Their plant indicators were demonstrated as an applicable method to detect atmos pheric fluoride. (Received January 14, 1975)