## 3 Results and Discussion
### Phenolic Content and the Antioxidant Activity  
The effects of N levels and N sources (fertilisers) on the antioxidant capacity, total phenolic content, and total flavonoid content of flowering Chinese cabbage are shown in Figure 2 and Table S3 (Supplementary Materials).  
Both effects (N level and N source) were statistically significant for all parameters in the pot and hydroponic cultivation systems (Table S1, Supplementary Materials).  
In hydroponics, the DPPH scavenging activity of the samples was higher, while the TEAC, FRAP, TPC and TFC values were lower in comparison to the samples from pot cultivation (Figure 3). In pot cultivation, irrespective of the N dose, the DPPH, FRAP, TPC and TFC values were the highest in the samples treated with Mg(NO\({}_{3}\))\({}_{2}\), whereas the TEAC values were the highest in the sample treated with NaNO\({}_{3}\). The maximum DPPH scavenging activity was 115.8 umol/g in the sample after the Mg(NO\({}_{3}\))\({}_{2}\) treatment at N-70 and the TEAC was 536.69 umol/g in the plant after the NaNO\({}_{3}\) treatment at N-90.  
Different conclusions can be drawn from the results obtained in hydroponic cultivation as the maximum values of the DPPH and TEAC scavenging activity were 122.41 umol/g DW and 409.51 umol/g of DW, respectively, both after the NH\({}_{4}\)NO\({}_{3}\) treatment. The highest FRAP was noted for Ca(NO\({}_{3}\))\({}_{2}\) at N-90 (24.12 mmol TE/g).  
The maximum individual value of the TFC value was observed in hydroponics for the samples fertilised with NaNO\({}_{3}\) (1.43 mg/g).  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**N Source**} & **N** & **Chl a, mg/g** & **Chl b, mg/g** & **Carotenoids** & **Chl a + Chl b**, & **Chl a/Chl b** & **(Chl a + Chl b)/(\(\star\) c)** \\  & **Level** & **DW** & **DW** & **(x + c), mg/g DW** & **mg/g DW** & **Chl a/Chl b** & **(Chl a + Chl b)/(\(\star\) c)** \\ \hline \multirow{4}{*}{NaNO\({}_{3}\)} & N-50 & 4.56 \(\pm\) 0.6 c\({}^{\mathrm{d}}\) & 1.27 \(\pm\) 0.24 c\({}^{\mathrm{d}}\) & 0.99 \(\pm\) 0.09 b & 5.83 \(\pm\) 0.90 \({}^{\mathrm{d}}\) & 3.60 \(\pm\) 0.16 b\({}^{\mathrm{c}}\) & 5.87 \(\pm\) 0.36 d\({}^{\mathrm{d}}\) \\  & N-70 & 4.10 \(\pm\) 0.10 d\({}^{\mathrm{d}}\) & 1.11 \(\pm\) 0.03 d\({}^{\mathrm{d}}\) & 0.99 \(\pm\) 0.00 b & 5.21 \(\pm\) 0.13 d\({}^{\mathrm{d}}\) & 3.69 \(\pm\) 0.00 b & 5.26 \(\pm\) 0.12 f \\  & N-90 & 3.42 \(\pm\) 0.10 f & 0.92 \(\pm\) 0.04 e & 0.84 \(\pm\) 0.03 c\({}^{\mathrm{d}}\) & 4.34 \(\pm\) 0.14 h & 3.71 \(\pm\) 0.05 b & 5.19 \(\pm\) 0.04 f \\  & Mean & 4.06 \(\pm\) 0.60 & 1.10 \(\pm\) 0.19 & 0.94 \(\pm\) 0.09 & 5.13 \(\pm\) 0.79 & 3.67 \(\pm\) 0.09 & 5.44 \(\pm\) 0.48 \\ \hline \multirow{4}{*}{Mean} & N-50 & 4.56 \(\pm\) 0.51 & 1.37 \(\pm\) 0.25 & 0.91 \(\pm\) 0.10 & 5.93 \(\pm\) 0.75 & 3.37 \(\pm\) 0.31 & 6.55 \(\pm\) 0.83 \\  & N-70 & 5.29 \(\pm\) 1.89 & 1.34 \(\pm\) 0.30 & 1.29 \(\pm\) 0.65 & 6.63 \(\pm\) 2.14 & 3.88 \(\pm\) 0.69 & 5.44 \(\pm\) 0.89 \\ \cline{1-1}  & N-90 & 4.18 \(\pm\) 0.83 & 1.20 \(\pm\) 0.33 & 0.88 \(\pm\) 0.05 & 5.39 \(\pm\) 1.16 & 3.53 \(\pm\) 0.25 & 6.06 \(\pm\) 1.02 \\ \hline \hline \end{tabular}  
* Values with the same letter within one type of cultivation for the parameter were not significantly different (_p_ > 0.05, Duncan’s test).  
\end{table}
Table 4: _Cont._Figure 3: Antioxidant activity (DPPH, TEAC, FRAP) of the flowering Chinese cabbage cultivated with various N nutrition sources.  
Figure 2: Phenolic content (TPC—total phenolic content, TFC—total flavonoid content) of the flowering Chinese cabbage cultivated with various N nutrition sources.