MANGANESE TOXICITY TO DIFFERENT GROWTH-PROCESSES IN-VITRO IN NICOTIANA

Manganese toxicity to germination, callus induction and shoot regenera tion was studied on three cultivars of Nicotiana tabacum: EEL W3, Burl ey 21, I)right NC 944. All materials were cultured on MS solid medium containing 0.1 (control), 2, 5, 10, 15 and 20 mM Mn, to which 5 mu M N AA and 5 mu M kinetin were added for callus induction and shoot regene ration. Mn toxicity to callus growth was tested using habituated callu s of Nicotiana bigelovii var. bigelovii grown on MS medium without gro wth regulators. Mn concentrations higher than 2 mM were toxic for germ ination, and concentrations higher than 5 mM were toxic for callus ind uction, shoot regeneration and callus growth. Among the cultivars exam ined, Bright tobacco appeared more tolerant to high Mn concentrations during callus formation and shoot regeneration. However, many regenera ted plants capable of growing in vitro in the presence of 2 and 5 mM M n were obtained.