Development of Teaching Materials for Environmental Education—The Influences of Heavy Metals on the Growth of Rice Plants and Duckweed—

Abstract

Teaching materials for environmental education were developed. The growth of rice plants was inhibited when they were cultivated in solutions of copper sulfate of 3. 2 ppm, 10 ppm and 32 ppm, and also in solutions of cobalt chloride of 10 ppm and 32 ppm. The rate of inhibition of the growth of rice plants was proportional to the concentration of the copper sulfate and cobalt chloride.

The growth of duckweed was inhibited by a 10 yen coin. After 5 days culture, the inhibition was observed for the first time in both Lemna paucicostata and Spirodela polyrhiza. All Lemna were dead after 7 days culture and all Spirodela were dead after 10 days culture. The influences of copper, zinc and tin, which are all components of a 10 yen coin, on the growth of Spirodela were examined separately. The growth of the plant was inhibited by copper and zinc, but not by tin. However, it was not clear from the results of this study which metal was stronger in inhibiting the growth of duckweed.