Abstract:Undaria pinnatifida is a commercially important seaweed in China with a more than 30 years of farming history. However, artificial seedling production of this seaweed has not yet been stable. How to control the light intensity according to seasonal changes of temperature is the key to the success of artificial seedling production in practice. In this investigation, we report our large-scale indoor artificial production of seedlings by use of spores at room temperature in Liaodong peninsula, the major farming area of U. pinnatifica in China, mainly on how to control irradiance levels during the 3-month period. According to the requirements of the gametogenesis resulted from our previous studies, we adopted two high irradiance phases (≥50 μmol photons /m2·s) at the beginning and the ending stage. The first high light phase started from seeding of zoospores and ended at the beginning of over-summering phase. This period allowed a full growth of male and female gametophytes. The second high light phase, starting from the end of the over-summering period to the end of the seedling production, allowed a rapid gametogenesis and formation of sporophytes. Under suitable irradiance the gametophytes were able to complete gametogenesis and produce normal young sporophytes even at temperature as high as 24 ℃. The optimal temperature for the growth of young sporophytes was 20~22 ℃. 2~5 mm sporophytes could temporarily tolerate 24~26 ℃, however, the smaller they were, the higher the capacity they demonstrated in tolerating higher temperature. Real-time manipulation of irradiance according to the temperature changes and the development of gametophytes over a period of 3 months generated very good results of seedlings on strings in 2010. This investigation will shed light on improvement of techniques in terms of seedling production in this region.
