Summary:

The paper presents the optimization process of obtaining plantlets of Stevia rebaudiana under in vitro culture conditions and describes the method for adjusting the rooted plants to ex vitro conditions. The low viability of seeds and poor germination are the reasons of difficulties in commercial cultivation of this species in Poland. Plant tissue and cell cultures are the techniques helping to overcome these limitations. Numerous shoots were obtained using sterile nodal segments that were cultured on solidified MS media and supplemented with phytohormones. Elongated shoots were transferred onto the rooting medium. Thus in vitro regenerated plantlets were acclimated to greenhouse conditions. The highest efficiency of shoots proliferation was observed at presence of 0.5 mg dm-3 BAP. The longest stems and the largest number of leaves and the greatest width of leaf were observed when 0.5 mg dm-3 GA3 was applied into medium. The process of rhizogenesis was intensified by the 0.5 mg dm-3 IBA contained in the nutrient medium. Under the influence of this phytohormone roots were the most numerous and the longest. At the stage of acclimatization 1/4 MS salt solution was used for irrigation of plantlets what supports increased of the process from 46% to 70% in comparison to use of water.