抄録
This study investigated the influence of cultural conditions on the cellular biovolume (VC) and gelatinous sheath volume (VG) of Staurastrum arctiscon (Charophyceae) and its growth characteristics during laboratory culturing. A unialgal culture isolated from Lake Biwa was incubated in modified M11 medium containing various concentrations of nitrogen and phosphorous in the form of nitrate and phosphate (0.01 or 0.1 mg P/L). The N/P mass ratio of the medium and incubation temperature ranges were 5 - 100 and 5 - 35°C, respectively. VC was lower at higher incubation temperature and higher nitrate concentrations, whereas VG increased with temperature. As VC and VG changed, the size of the gelatinous sheath increased relative to the cellular biovolume (VR) with the water temperature and nitrate concentration. The enhanced growth rate and net production rate with a rising temperature were considered to contribute to the decreased VC and increased VG. The positive effect of nitrate concentration on VG was believed to be attributable to the enhanced net production rate with higher nitrate concentrations.
