In order to clarify the growth characteristic under high water temperature of young sporophyte of intraspecific crossbreeding of Undaria pinnatifida (NT) between Naruto cultivar (NN) and Tsubaki natural strain (TT) from Tokushima prefecture in Japan, we carried out laboratory culture experiments at 5℃ interval from 5℃ to 30℃ and 1℃ interval from 25℃ to 30℃ under a light intensity of 100 µmol photons m^{-2}s^{-1} in 11 L ： 13 D. The optimal temperature of three strains after 15 days in culture was the range of 15 - 20 ℃. The upper critical temperatures in growth of NN and NT were 26℃, while that of TT was 27℃. NN and NT survived until 6 days and 12 days in culture at 27℃, respectively. The blade of NN withered like melting in medium at 27℃. On the other hand, the blade of NT had a bit curly unattached for substratum. Therefore, it was thought that the crossbreeding strain of NT had a middle level of the high water temperature tolerance between NN and TT.
Undaria pinnatifida
crossbreeding
growth
high-temperature tolerance