抄録
Optimal conditions for sorus formation of Laminaria japonica were investigated by culturing discs of the sporophyte in bottles. All discs formed sori in the seven combinational conditions of temperature (5-15°C), irradiance (33.2-116 μE•m-2•s-1) and photoperiods (16:8, 12:12 and 8:16h LD) in nutrientrich medium. Sorus formation occurred earlier at 15°C than at 5 and 10°C and were largest in the area at 15°C. Sori grew larger under high irradiance (116 μE•m-2•s-1) than under low irradiances (66.4 and 33.2 μE•m-2•s-1), but the initiation of sorus formation was not influenced by irradiance. Sorus formation was earlier in 8:16h LD than in 12:12 and 16:8h LD. Rapid formation of large sori occurred at high temperatures even in a long photoperiod. Sorus formation in discs in nutrient-poor medium was slower than that in discs in nutrient-rich medium, in which all discs formed large sori. Most discs in nutrient-poor medium formed very small sori. These results indicate that water temperature and nutrient conditions strongly affect both to the induction and expansion of sorus formation.
