## 3 Results and Discussion  
### Micropropagation of P. tomentosa \(\times\) P. fortunei  
The disinfection method resulted in 80% effectiveness. All of the survived explants responded to a half-strength MS medium with 1 mg/L BAP. Removing PPM during the multiplication stage from the medium did not cause endogenous contamination. For the multiplication stage, the MS2 medium was the most effective. Each node, after 4 weeks of culture, produced two new shoots with 3.5 culturable nodes on each, thus giving seven culturable nodes per explant. According to [PERSON] et al. [11], using the same medium, but with a light intensity of 3000 lm after six weeks, six culturable nodes of _P. fortunei_ were obtained. The differences could be explained as a result of using a temperature of 28 \({}^{\circ}\)C, a 14 h photoperiod for culture incubation, and non-hybrid plant usage. Shoot tips had great elongation ability with poor axillary bud formation. Explants using the MS1 medium showed one or two axillary bud formations, however, shoots were in poor condition and stopped growing. In some cases, roots also occurred. A high concentration of BAP in the MS3 medium resulted in callus growth and callus of the tissue. Shoots were often vitrified. The effect of different mediums on the explant is summarized in Table 3.  
Explants cultured under limited light conditions exhibited great elongation of shoots during the four-week period, and callus proliferation. Each node provided two elongated, yellowish shoots with six culturable nodes so, per explant, there were 12 culturable nodes. [PERSON] et al. [11] obtained eight culturable nodes using the same medium in 1200 lm light intensity after six weeks. Four week old callus with regenerating shoots was sub-cultured on MS2 and normal light conditions were used. After 4 weeks, 34 shoots were regenerated from callus. Plants were healthy and green but most of them had a variable number of leaves (one, two, three or four) in a whorl, instead of two. Because of these frequent variations, it is not recommended that such plants be used for further cultivation. Phenotype variations in plants regenerated from callus are very common and were also observed in potato [13] or _Curcuma aromatica_[14]. [PERSON] and [PERSON] [8], using direct somatic embryogenesis, obtained 69.8 plants from leaf explants, and 58.5 _P. elongata_ plants from internodal explants. Interesting results were obtained by [PERSON] and [PERSON]. [15] who investigated different _Paulownia_ species and hybrids using MS medium with 0.5 mg/L BAP and 0.01 mg/L indole-3-butrytic acid (IBA). The result was a great number of internodes with _P. elongata_ obtaining 55.2 internodes, _P. tomentosa_\(\times\)_P. fortunei_ obtained 33.54 internodes, and the complex hybrid, (_Pelongata_\(\times\)_P. tomentosa_) \(\times\)_P. elongata_ obtained 44.67 internodes. This indicates a high potential for propagation of the _Paulownia_ using this method to obtain a great number of nodes. Rooting methods turned out to be very effective. The first roots appeared in both media after 2 weeks. MS4 medium induced rooting in 95% of shoots. Roots were long and well branched. It was also very easy to remove agar from the roots (Figure 1A). MS5 medium induced rooting in 100% of shoots. However, roots were thick, short, and tended to break when agar was removed. Because of the problems connected with washing out agar from the roots and the high percentage of damaged roots (data not shown), the MS5 medium was considered unsuitable for commercial use. Despite the lower success rate of rooting in the MS4 medium, this medium was used for rooting and acclimatization due to the ease in handling (Table 4). Plants were very efficiently acclimatized with a 90% success rate. Ventilation of the mini greenhouses was also crucial in the hardening stage because this prevented fungal infections. Abundant watering favored the fast growth of the plants (Figure 1B). Figure 1: _P. tomentosa_\(\times\)_P. fortunei_ rooting and acclimatization. (**A**). _P. tomentosa_\(\times\)_P.