Algae. 2001; 16(4): 437-443.

Mixed-phase Reproduction of Dasysiphonia chejuensis from Korea: Nuclear DNA Contents and Environmental Factors

Han-Gu Choi, Kwang Young Kim

School of Biological Sciences, Seoul National University , Department of Oceanography, Chonnam National Universit

Dasysiphonia chejuensis I.K. Lee et West (Dasyaceae, Ceramiales) showed a mainly Polysiphonia-type life history in culture but female plants occasionally formed tetrasporangia. Nuclear DNA contents of tetrasporangial mother cells from normal tetrasporophytes and female/tetrasporangial mixed-phase plants as well as cells of carpogonial branches were estimated from DAPI-staining, using image processing. In frequency distribution patterns, the DAPI-stained nuclear volume (NV) of tetrasporangial mother cells from female/tetrasporangial mixed-phase plants and normal tetrasporophytes showed three peaks corresponding to 4C/8C/16C and 8C/16C/32C, respectively. A carpogonium has one nucleus but the rest three cells of the carpogonial branch have two niclei. The NV of four cells in carpogonial branches showed two peaks corresponding to 2C and 4C. The polygenomy of the nuclear genome in uninucleate reproductive cells such as tetrasporangia and carpogonia may provide red algae with a genetic buffering mechanism that protects them from potentially lethal mutations during fertilization and meiosis. The most favorable condition for the occurrence of mixed phases was 15℃, 20 μmol photons?m-2?s-1 and 16:8 LD, which was also one of the most favorable conditions for the growth of tetraspore germlings. The occurrence of mixed-phase plants, however, was different depending on various environmental factors and developmental stages of each plant in culture and it was generally high in the old stage of plants cultured.

Keywords : culture, Dasysiphonia chejuensis, environmental factors, mixed-phase reproduction, nuclear DNA contents