Promotion of callus propagation by 5-aminolevulinic acid in a Laminaria japonica sporophyte

The effects of 5-aminolevulinic acid (ALA) on the induction and growth of callus-like cells in Laminaria japonica were investigated in explants obtained from basal, middle and apical portions along the sporophyte. 5-Aminolevulinic acid treatment promoted the induction of callus-like cells in explants obtained from all portions, and the induction rate was higher when a concentration of 50-500 mg L-1 of ALA was used. The promotion was especially remarkable in apical explants, and the induction was 10-14 times higher in the 100-500 mg L-1 range than that in the 0 mg L-1. The cell division rate of callus-like cells showed the highest value in the explants cultured with 500 mg L-1 of ALA for 14 days. The promotion of the cell division rate by culturing with 500 mg L-1 ALA was also observed under white, blue and red lights. The callus-like cells, which were cultured in 500 mg L-1 of ALA for 2 months, had many clear chloroplasts. After 3 months, young thalli occurred. These results suggest that the ALA treatment is effective for stable propagation of callus-like cells in L. japonica.