## 3 Results
### Determination of Content of Photosynthetic Pigments  
After three months of in vitro culture, the concentrations of chlorophyll \(a\) in the blackberry plantlets ranged from 10.26 ug g\({}^{-1}\) FW (treatment with 30 mg dm\({}^{-3}\) ZnONPs) to 12.83 ug g\({}^{-1}\) FW (treatment with 20 mg dm\({}^{-3}\) ZnONPs) (Figure 4). The content of chlorophyll \(b\) ranged from 17.60 ug g\({}^{-1}\) FW (treatment with 40 mg dm\({}^{-3}\) ZnONPs) to 20.74 ug g\({}^{-1}\) FW (treatment with 10 mg dm\({}^{-3}\) ZnONPs), and that of total chlorophyll from 28.25 ug g\({}^{-1}\) FW (treatment with 40 mg dm\({}^{-3}\) ZnONPs) to 33.05 ug g\({}^{-1}\) FW (treatment with 20 mg dm\({}^{-3}\) ZnONPs). The plants had the lowest content of chlorophyll \(a\) and total chlorophyll in the control treatment (Figure 4), and the chlorophyll \(b\).\(a\) ratio was 1.62. Plants grown on the medium with 10 and 20 mg dm\({}^{-3}\) ZnONPs had a similar content of chlorophyll \(a\) and \(b\) to the control, and the chlorophyll \(b\).\(a\) ratio was 1.70 and 1.58, respectively (Figure 4). In these samples, there was also a statistically significant increase in the total chlorophyll concentration. Higher concentrations of zinc oxide nanoparticles, i.e., 30 and 40 mg dm\({}^{-3}\), caused a statistically significant reduction in the concentration of chlorophyll \(a\) and total chlorophyll, and in the treatment with 40 mg dm\({}^{-3}\), in the  
Figure 2: Effect of different concentrations of ZnONPs [mg dm\({}^{-3}\)] on total phenolic content (TPC) in plantlets of blackberry (_Rubus friticosus_ L.), Navaho variety. Error bars represent \(\pm\) SD. Different lowercase letters indicate significant differences at \(p\) = 0.05.  
content of chlorophyll \(b\) as well. The chlorophyll \(ba\) ratio was highest in the treatment with 30 mg dm\({}^{-3}\) ZnONPs, at 1.96, while for the highest concentration of nanoparticles it was 1.65, which was similar to the control. Carotenoid concentrations in the blackberry plantlets ranged from 3.90 ug g\({}^{-1}\) FW to 4.88 ug g\({}^{-1}\) FW (Figure 4). Zinc oxide nanoparticles reduced the content of carotenoids in the blackberry plantlets; the correlation coefficient between the concentration of ZnONPs and the content of carotenoids was \(-\)0.097. Statistically significant differences in the content of carotenoids were noted for the treatments with 20-40 mg dm\({}^{-3}\) ZnONPs and the control. Effect of Bacillus thuringiensis Bacteria on the Growth and Development of Blackberry Plantlets in Ex Vitro Cultivation  
After three months of in vitro culture, the blackberry plantlets were planted in soil (Figure 5). Plants from each in vitro experimental treatment were divided into two groups. Figure 4: Effect of different concentrations of ZnONPs [mg dm\({}^{-3}\)] on chlorophyll and carotenoid concentrations in plantlets of blackberry (_Rubus friticosus_ L.), Navaho variety. Error bars represent \(\pm\) SD. Different lowercase letters indicate significant differences at \(p=0.05\). Figure 3: Effect of different concentrations of ZnONPs [mg dm\({}^{-3}\)] on total antioxidant capacity (TAC) in plantlets of blackberry (_Rubus friticosus_ L.), Navaho variety. Error bars represent \(\pm\) SD. Different lowercase letters indicate significant differences at \(p=0.05\). One was inoculated with bacteria (Bacteria+), while the other was not inoculated (Bacteria\(-\)). The development of the plantlets was assessed after one month of ex vitro cultivation. Plantlets from the in vitro control were generally larger than plantlets from the treatments with ZnONPs. In comparison with the control, the shoot number and length were statistically significantly lower for the plantlets from the treatments with 30 and 40 mg dm\({}^{-3}\) ZnONPs, and the root number and length were significantly lower for 10-40 mg dm\({}^{-3}\) ZnONPs (for both Bacteria+ and Bacteria-). Inoculation of the substrate with _B. thuringiensis_ promoted the development of all plantlets obtained in vitro.