## 4 Discussion
### Artificial Lighting
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Unit** & **F110** & **F220** & **L110** & **L220** \\ \hline \(9^{\prime}\)\({}_{C}\)- & & & & & \\ Neoxanthin & & \(0.292\pm 0.028\) & \(0.294\pm 0.030\) & \(0.287\pm 0.016\) & \(0.295\pm 0.031\) \\ Violaxanthin & & \(0.415\pm 0.042\) & \(0.415\pm 0.048\) & \(0.427\pm 0.032\) & \(0.468\pm 0.026\) \\ Antheraxanthin & & \(0.038\pm 0.003\) & \(0.037\pm 0.004\) & \(0.040\pm 0.007\) & \(0.032\pm 0.005\) \\ Lutein & mg g\({}^{-1}\) DW & \(0.875\pm 0.085\) & \(0.855\pm 0.105\) & \(0.801\pm 0.061\) & \(0.861\pm 0.071\) \\ Zexanathin & & \(0.042\pm 0.006\) & \(0.039\pm 0.002\) & \(0.051\pm 0.013\) & \(0.036\pm 0.007\) \\ Chlorophyll \(b\) & & \(2.243\pm 0.217\) & \(2.141\pm 0.190\) & \(2.126\pm 0.155\) & \(2.252\pm 0.236\) \\ Chlorophyll \(a\) & & \(6.282\pm 0.533\) & \(5.950\pm 0.508\) & \(6.032\pm 0.451\) & \(6.269\pm 0.594\) \\ \(\beta\),\(\beta\)-Carotene & & \(0.335\pm 0.012\) & \(0.323\pm 0.038\) & \(0.320\pm 0.035\) & \(0.354\pm 0.043\) \\ \hline _ratios_ & & & & \\ Chl _b_:Ch \(a\) & & \(0.357\pm 0.005\) & \(0.360\pm 0.002\) & \(0.350.003\) & \(0.359\pm 0.008\) \\ \(\beta\),\(\beta\)-Car: & & \(0.053\pm 0.004\) & \(0.054\pm 0.002\) & \(0.053\pm 0.003\) & \(0.056\pm 0.003\) \\ Chl \(a\) & & \(0.265\pm 0.003\) & \(0.275\pm 0.009\) & \(0.266\pm 0.005\) & \(0.270\pm 0.008\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Photosynthetic pigments concentrations (mean \(\pm\) sd) in _H. portulacoides_ leaves (\(n=5\)). DW—dry weight. observation is that leaves from low-density plants were probably exposed to higher irradiance for a longer time-period than high-density plants due to less shading. Even though the type of light did not seem to affect photosynthetic pigments in _H. portulacoides_, an increase in the concentration of carotenoids, which include xanthophylls and caroten, has been observed in leafy vegetables exposed to blue LEDs [29; 54]. For instance, several _L. sativa_ varieties, cabbage (_Brassica rapa_ L. and _B. oleracea_ varieties) and water spinach (_Ipomoea aquatic_ Forssk.) displayed an increase in the concentration of chlorophylls and other pigments when growing under blue LEDs [49; 55; 56; 57; 58; 59]. Nonetheless, some _L. sativa_ varieties displayed similar concentrations regardless of exposure to fluorescent lights or LEDs [60; 61], highlighting the complexity of the effects of light quality in plant physiology. One key aspect to consider when choosing the type of lighting system to cultivate plants in a controlled environment is energy efficiency. In the present study, the wattage of one fluorescent lamp was 54 and one LED unit was 30 W. Therefore, operating on a 14:10 light-dark photoperiod, a fluorescent lamp consumed 0.76 and a LED unit 0.42 kWh day\({}^{-1}\). Considering that one fluorescent lighting system was composed of two lamps consuming a total of 1.52 kWh day\({}^{-1}\), and one LED lighting system was composed of three LED tiles consuming 1.26 kWh day\({}^{-1}\), lighting energy costs were reduced by 17% just by using LEDs. Operating costs could be driven down even further by employing LEDs in _H. portulacoides_ hydroponic production since their lifespan and maintenance costs are typically lower than fluorescent lights [28]. Despite requiring a higher initial investment, LEDs are likely more cost-efficient given their potentially higher energy efficiency, longer lifespan, and lower maintenance cost [62]. Since _H. portulacoides_ was seemingly unaffected by the type of artificial lighting tested, the LEDs can be seen as a suitable cost-efficient alternative to fluorescent lights. \begin{table}
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**Species** & \begin{tabular}{c} **Hydroogenic** \\ **Technique** \\ **(Days)** \\ \end{tabular}  & \begin{tabular}{c} **Growth** \\ **Period** \\ **(Days)** \\ \end{tabular}  &