The algae were cultured in a sterilized f/2 media treated with BR at concentrations of 0, 5, 10, 50 μg/L for P. subcordiformis, and 0, 1, 5, 10 μg/L for I. Galbana. The cultures were maintained in 12:12 Light-dark cycles at 5000-10000 lx, 16 - 23°C for P. subcordiformis and at 1500-3000 lx, 20-23°C for I. galbana. The growth of the algae during one week of BR treatment was measured with spectrophotometer every morning. Chlorophyll, photosynthesis, nucleic acid, carbohydrate, protein and vitamin C in the algae were measured after 4 days of BR treatment (10 μg/L and 5 μg/L for P. subcordiformis and I. galbana respectively). The results show that algae cells multiplications were promoted at low BR concentrations (1, 5μg /L for I. galbana and P. subcordiformis respectively). The growth constants were 0.23 in the control, 0.27, 0.29, 0.27 in the treated group for P. subcordiformis. Similarly, they were 0.25 in the control, 0.28, 0.30, 0.29 in treated group for I. Galbana. The lag phase of growth was shortened about 0.5 day in every treated group. The optimum concentration of BR used for P. subcordiformis was 10 μg/L; it was 5 μg/L for I. galbana (Tab. 1). Chlorophyll content and photosynthetic rate increased by 10.6% and 16.75% respectively for P. subcordiformis and 10.5% and 16.48% respectively for I. galbana in treated groups. Dry weight of P. subcordiformis treated with BR was 0.901 g/L and it was 0.622 g/L in the control. The increases of nucleic acids in treated groups were 37.4%, 35.50% (RNA) and 26.3%, 25.0% (DNA) in P. subcordiformis and I. galbana respectively (Tab. 2). In addition, carbohydrate, protein, and vitamin C in the algae increased by 4.4%, 14.3%, 22.7% and 5.68%, 13.3%, 23.3% respectively after BR treatment (Tab. 3).

It may be concluded from these results that BR apparently has a growth promoting effect on the algae and can also improve the nutritive values of the algae. When cultures of the algae are treated with proper amount of BR, the yield will be increase.