2,4-DICHLOROPHENOXYACETIC ACID AFFECTS MODE AND FREQUENCY OF REGENERATION FROM HYPOCOTYL PROTOPLASTS OF BRASSICA-OLERACEA

The effect of 2,4-dichlorophenoxyacetic acid (2,4-D) on the regenerati on from hypocotyl protoplasts of Brassica oleracea was studied by vary ing the 2,4-D concentration in the protoplast culture medium, 8 p, and the callus proliferation medium, K3. When hypocotyl protoplasts of th e inbred line BL12 were cultured in the complete absence of 2,4-D, the y divided and produced embryogenic calli. Moreover, these calli genera ted somatic embryos which were easily recognized by red cotyledons due to the presence of anthocyanin. When 2,4-D was present either in 8p m edium or K3 medium the formation of somatic embryos was reduced. On th e other hand, the number of shoot-forming calli increased considerably . We therefore conclude that 2,4-D directs the mode of regeneration by suppressing somatic embryogenesis in favour of shoot regeneration. Se condly, 2,4-D increases the regeneration efficiency. Furthermore, the callus proliferation phase on K3 medium is most important with respect to the determination of either somatic embryogenesis or shoot regener ation.