Abstract
We investigated the cumulative thermal constant and threshold temperature for the development of male flowers in Metasequoia glyptostroboides. The threshold temperature for the development of male flowers was approximately 0°C and the cumulative thermal constant was approximately 175°C/day. The male flowers of M. glyptostroboides bloomed earlier than those of Cryptomeria japonica (Tateyama-sugi and Boka-sugi) at 10°C in controlled environment rooms. From these results, it is inferred that the patients with Japanese cedar pollinosis are affected by the pollen of M. glyptostroboides earlier than that of C. japonica if there are trees of M. glyptostroboides in the neighborhood.
