Selenium (Se) is an essential microelement for human health and has antioxidant and anticancerous properties. One of the ways to increase its concentration in plants is biofortification through various agronomic practices including artificial lighting. The aim of this study was to determine the responses of baby leaf lettuce to various Se content in hydroponic solution at different ratios of blue (B) and red (R) light of light-emitting diodes (LED) lighting. Lettuce (Lactuca sativa, ‘Little Gem’) was grown hydroponically under B:R light ratios–10%B:90%R, 75%B:25%R. The photon flux density (PFD), photoperiod, temperature, and relative humidity in the growth chamber were maintained at 220 μmol m−2 s−1, 18 h, 21/17 ± 2 °C, and 60 ± 5%, respectively. Two experiments with Se were performed using natrium selenate (Na2SeO4). Results of the first experiment (Se–0, 1, 3 ppm) showed that the content of Se in lettuce was about 15 times higher at 3 ppm compared to 1 ppm. Similar trends were observed for both B and R ratios. However, even the lowest dose of Se in hydroponic solution inhibited lettuce growth and reduced photosynthesis and chlorophyll content. Therefore, a second experiment was performed with lower Se doses (0, 0.5, 1 ppm) at different growth stages (11th and 17th days after sowing (DAS)). It was found that, when Se exposure was initiated at the 17th DAS, the lettuce accumulated a lower content of Se compared to the 11th DAS, but this did not have a negative effect on their growth. The B:R ratio of 10B:90R% resulted in a higher content of Se in the leaves. Overall, these results suggest that properly composed doses of Se, LED lighting and application time could be a suitable way for cultivation of selenium-biofortified baby leaf lettuces without any adverse effects on growth.
The Effect of Adding Sugar and Salt to Hydroponic Solution for Coloring of Red Leaf Lettuce under Plant Factory Condition
