The growth of apical and intercalary fragments of a red alga, Gracilariopsis chorda (Holmes) Ohmi in unialgal culture

Abstract

In order to increase the algal fresh weight of a red alga, Gracilariopsis chorda (Holmes) Ohmi, with indoor culture, four kinds of the algal fragments (5A: 5 mm long apical, 5I: 5 mm long intercalary, 3I: 3 mm long intercalary, 2I: 2 mm long intercalary fragments) were evaluated to determine a suitable starting material for unialgal culture. During the unialgal culture, new multiple branches grew from a regeneration surface of intercalary fragments. Although the algal fresh weight after eight weeks of cultivation were significantly larger in 5A and 5I than in 3I and 2I, the rate of increase (i.e., the ratio of the fresh weight to initial fresh weight after eight weeks of cultivation) were in the order of 5I (53.0-fold), 3I (80.4-fold), 5A (93.7-fold), and 2I (114-fold). The relative growth rate (RGR) of 5A was higher than that of 2I before three weeks of cultivation, but after four weeks of cultivation RGR of 2I was higher than that of 5A. From these results, among the algal fragments tested, 2I seems to be the best initial fragment for G. chorda unialgal culture. On 20 l scale culture, the average fresh weight of 2I was 7.28 g/tank after eighth week culture.