SOMATIC EMBRYOGENESIS, ORGANOGENESIS AND CALLUS GROWTH-KINETICS OF FLAX

The effects of plant growth regulators (PGR) on calli induction, morph ogenesis and somatic embryogenesis of flax were studied. The organogen ic and callus formation capacity were assessed for different types of source explants. Root and shoot explants were equally good material fo r calli production but the former produced calli without shoot regener ation capacity. Under the experimental conditions tested, 2,4-dichloro phenoxyacetic acid (2,4-D) + zeatin was the most efficient PGR combina tion on calli induction and biomass production. The calli were green b ut with no rhizogenic capacity. In contrast, and at similar concentrat ions, indole-3-butyric acid (IBA) + kinetin induced white or pale gree n friable calli with a good root regeneration capacity (60%). A factor ial experiment with different combinations of 2,4-D + zeatin + gibbere llic acid (GA(3)) levels revealed that the direction of explant differ entiation was determined by specific PGR interactions and concentratio ns. The results from these experiments revealed that the morphogenetic pathway (shoot versus root differentiation) can be manipulated on fla x explants by raising the 2,4-D level from 0.05 to 3.2 mg l(-1) in the induction medium. The induction and development of somatic embryos fr om flax explants was possible in a range of 2,4-D + zeatin concentrati ons surrounding 0.4 mg l(-1) 2,4-D and 1.6 mg l(-1) zeatin, the most e fficient growth regulator combination.