## 3 Results and Discussion
### Colour Measurement  
The results of the instrumental colour measurements expressed as the L* (lightness), a* (red/green) and b* (yellow/blue) coordinates are shown in Figure 1 and Table S2 (Supplementary Materials). Both effects, of the N source and the N level, were statisti  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**N Source** & **N Level** & **Fe** & **Mn** & **Zn** & **Cu** & **Na** \\ \hline \multirow{6}{*}{NH\({}_{4}\)NO\({}_{3}\)} & N-50 & \(116.3\pm 10.6\) deg* & \(32.4\pm 2.80\) b  & \(76.4\pm 0.80\) b-d & \(7.64\pm 0.30\) a  \\  & N-70 & \(109.1\pm 3.08\) b-d & \(32.4\pm 4.59\) b  & \(79.8\pm 1.80\) b-d & \(7.88\pm 0.66\) a  & \(0.090\pm 0.01\) b  \\  & N-90 & \(125.1\pm 7.10\) e  & \(36.3\pm 3.11\) c-e  & \(81.9\pm 0.86\) e-c  & \(5.74\pm 0.24\) a  & \(0.127\pm 0.01\) d  \\  & Mean & \(116.9\pm 10.01\) BC* & \(33.7\pm 2.22\) A  & \(79.4\pm 4.24\) C  & \(7.09\pm 1.05\) A  & \(0.097\pm 0.02\) B  \\ \hline \multirow{6}{*}{Ca(NO\({}_{3}\))\({}_{2}\)} & N-50 & \(93.7\pm 4.20\) a  & \(32.9\pm 5.60\) b  & \(72.6\pm 2.74\) b  & \(5.30\pm 0.68\) a  & \(0.057\pm 0.01\) a  \\  & N-70 & \(101.6\pm 7.78\) ab  & \(33.7\pm 1.68\) b  & \(62.4\pm 1.90\) a  & \(5.45\pm 0.20\) a  & \(0.077\pm 0.01\) ab  \\  & N-90 & \(106.5\pm 4.74\) b-d & \(39.3\pm 4.43\) e  & \(77.3\pm 0.27\) b-d & \(6.34\pm 0.34\) a  & \(0.097\pm 0.01\) b  \\  & Mean & \(100.6\pm 7.82\) A  & \(35.3\pm 3.45\) A  & \(70.8\pm 7.50\) A  & \(5.70\pm 0.99\) A  & \(0.077\pm 0.02\) A  \\ \hline \multirow{6}{*}{Ca(NO\({}_{3}\))\({}_{2}\)} & N-50 & \(94.1\pm 0.78\) a  & \(32.6\pm 4.67\) b  & \(90.1\pm 1.76\) e  & \(8.30\pm 0.80\) a  & \(0.080\pm 0.01\) b  \\  & N-70 & \(103.1\pm 1.29\) a-c  & \(34.2\pm 3.66\) b  & \(84.8\pm 2.30\) deg  & \(13.96\pm 0.97\) b  & \(0.093\pm 0.01\) b  \\  & N-90 & \(139.4\pm 0.26\) f  & \(39.1\pm 1.35\) de  & \(84.3\pm 0.74\) de  & \(17.99\pm 2.85\) d  & \(0.117\pm 0.01\) cd  \\  & Mean & \(112.2\pm 19.61\) B  & \(35.3\pm 3.26\) A  & \(86.4\pm 4.37\) D  & \(13.42\pm 4.36\) B  & \(0.097\pm 0.02\) B  \\ \hline \multirow{6}{*}{NaNO\({}_{3}\)} & N-50 & \(114.6\pm 9.09\) c-e  & \(35.6\pm 0.44\) b-d  & \(78.8\pm 2.47\) b-d  & \(8.09\pm 0.98\) a  & \(0.200\pm 0.03\) e  \\  & N-70 & \(116.9\pm 5.79\) de  & \(33.4\pm 3.13\) b  & \(76.1\pm 0.74\) b-d  & \(5.73\pm 0.34\) a  & \(0.340\pm 0.03\) f  \\  & N-90 & \(137.9\pm 6.27\) f  & \(34.5\pm 1.62\) b  & \(77.2\pm 0.37\) b-d  & \(7.26\pm 0.36\) a  & \(0.733\pm 0.01\) g  \\  & Mean & \(123.1\pm 12.71\) C  & \(34.5\pm 1.76\) A  & \(77.4\pm 2.33\)cally significant in the pot and hydroponic cultivation systems (Table S1, Supplementary Materials). The results of pot cultivation indicated that the highest L* values were obtained for the urea fertilisation (mean L* value of 46.4 for all the N doses), whereas the lowest were obtained for Ca(NO3)2 (mean L* value of 43.8). Lightness (L*) of the flowering Chinese cabbage samples treated with Mg(NO3)2 increased with increasing N levels, while the L* value of the samples treated with urea decreased. With regard to the a* value, treatment of the plants with urea resulted in the highest a* values (mean a* value of \(-\)5.79). Fertilisation with increasing N levels of NH4 NO3 and Ca(NO3)2 resulted in an increase in the a* values. The lowest a* value (\(-\)8.72) was determined for the flowering Chinese cabbage treated with Mg(NO3)2 at N-70. The values of the b* colour coordinate were the highest for the sample treated with Mg(NO3)2. However, there was no evident trend in the b* value changes with the increasing N dose of Mg(NO3)2. In contrast, the b* values of the samples treated with urea increased from 19.3 to 21.2 with increasing N doses, whereas the b* value decreased with increasing N doses of NaNO3. Both the chroma (C) and hue angle (h) values were the lowest in the samples fertilised with urea (Table S2). In hydroponic cultivation, the highest L* value (50.77) was determined in the flowering Chinese cabbage treated with Mg(NO3)2 at N-90.