Agronomic Characteristics and the Effects of Light on the Leaf Color Among Purple Leaf and Yellow Leaf Rice Cultivars

The purple leaf and yellow leaf rice cultivars are recently gathering attention in order to make rice field arts or dry flowers at many districts in Japan. Rice field art is a huge artwork of figures or letters drawn in the rice field by planting rice cultivars that have leaf color mutation or colored panicles. We surveyed the agronomic characteristics of nine purple leaf and two yellow leaf rice cultivars and the effects of light on the leaf color under three kinds of covering materials (UV-cut film, black cloth and transparent film). The leaf colors were evaluated by a color-difference meter and anthocyanin contents. The nine purple leaf rice cultivars showed a large variation in heading date, culm length and leaf anthocyanin contents. The contents differed more than 10-fold among the cultivars and the hue changed from red to greenish with the change in content. The leaf hue became greenish under shading especially with UV-cut film; therefore, ultra-violet proved to be necessary for anthocyanin production. The yellow leaf cultivars contained no anthocyanin. The leaf hue of yellow leaf rice cultivar became greenish under shading especially with a black cloth (50% cut of sunlight). Furthermore, the rice leaf colors among five cultivars were evaluated using a color-difference meter, an anthocyanin meter and a green meter (SPAD), and the difference of leaf colors was clearly shown.