Stimulation of shoot regeneration on Linum hypocotyl segments by thidiazuron and its response to light and calcium

The basal segment from hypocotyl of Linum usitatissimum L. seedling readily regenerates, to produce a large number of shoots, in a short period of 5 - 7 d. This response was stimulated by a low concentration (0.1 muM) of thidiazuron (TDZ). TDZ was also effective in inducing regeneration in dark. A drastic reduction in regeneration response on hormone-free as well as TDZ-supplemented medium was found after inclusion of an inhibitor of calcium-uptake, lanthanum (La3+). An essentiality of calcium in the regeneration was also evidenced by an increased response with increasing concentration of calcium. At Ca2+ concentration insufficient for regeneration, inclusion of TDZ resulted in shoot formation.