Doing propagation of paulownia from seed resulted in the recombination of properties, new plants are not identical to the mother plant, and plantations with these seedlings result in poor timber production. Most of the plant nursery centers in the Republic of Croatia carry out the propagation of paulownia by root cuttings (vegetative) or import planting material. Using the contemporary method, micropropagation technique (plants tissue culture in vitro) imposes itself on its superiority to obtain a large number of uniform, healthy and certified planting material. This graduate thesis at the Faculty of Agrobiotechnical Sciences Osijek, Department of Pomology, Viticulture and Enology (Pomology Laboratory) examines the possibility of optimizing the propagation protocol of Paulownia cultivar Bellissia (Paulownia elongata F2) in tissue culture in vitro. The conventional production model on the semi-solid nutrient medium was compared with the next-generation temporary immersion bioreactor (TIB / TIS system). The treatments included the application of two chelating forms of iron (FeNaEDTA and FeEDDHA). Process automation, using a temporary immersion bioreactor (TIB system), which uses liquid medium has greatly accelerated and reduced costs by removing agar in the complete micropropagation cycle of Paulownia. Significant differences were found between applied treatments and models. Cultivation of plants in temporary immersion bioreactors is extremely suitable if we need the rapid production of fresh biomass. The use of the DKW medium with modification, i.e. substitution of the commonly used FeNaEDTA iron form with FeEDDHA chelate is very effective in micropropagation of Paulownia Bellissia cultivars.