イネ

The effect of growth temperature on the character manifestation in a xantha mutant of rice (CM-14), which was induced by n-nitroso-n-methylurea treatment, was investigated. The phenotype of xantha seedling was distinctly modified by temperature, having orange yellow leaves at 20℃ and light green leaves at 30℃. Therefore, the amounts of chlorophyll and carotenoid in the expanded third leaf was used as a indicator of character manifestation. The chlorophyll content was negligible at 20℃, whereas it was about 55% of wild type at 30℃. The carotenoid content was unchanged at any temperature, showing nearly the same content as the wild type. When the chlorophyll-deficient xantha seedlings grown in the light at 20℃ were transferred after the emergence of their third leaf to 25℃ or 30℃, the third leaf formed chlorophyll. This result is distinctly different from that obtained in the virescent mutants, in which the chlorophyll content was never changed when they transferred after the emergence of their third leaf from 20℃ to 30℃. On the other hand, when the green xantha grown at 30℃ were transferred to 20℃, chlorophyll content was unchanged. When etiolated xantha seedlings grown in the dark at 30℃ were exposed to incandescent light at 20℃ for various periods of time and then they illuminated at 30℃, all of the seedlings had a certain chlorophyll content, however, they reached this content quickly with increase in period of illumination at 20℃. It is thought from these results that the xantha is a mutant inhibited by low temperature from chlorophyll synthesis in the light.