Adventitious shoot primordia were formed on horseradish hairy root cultured in dark. Plantlet formation frequency from the primordia was higher than that from root fragments. Culture for 26 days provided the adventitious shoot primordia, which had the highest potential for plantlet formation (53% explants at 40 days). Benzyladenine supplementation in the dark caused primordium enlargement, but did not increase the number of primordia formed. After adventitious shoot primordia were encapsulated with calcium alginate, kinetin supplementation (2.0-4.0 μM) increased the shoot formation frequency (65-80% explants at 20 days) in the light, but also promoted the undesirable formattion of multiple shoots. Supplementation with naphthaleneacetic acid (0.27-5.4 μM) in the calcium alginate beads in light enhanced the root emergence from primordia without inhibition of plantlet formation when the encapsulated beads were put on the agar-medium without naphthaleneacetic acid.
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