In this study, we identified and determined the content of phenolic compounds in Lilium candidum adventitious bulbs formed in vitro. HPLC analysis revealed the presence of four phenolic acids: chlorogenic, caffeic, p-coumaric, and ferulic acid. Phenolic acid content was assessed in adventitious bulbs formed in vitro on media supplemented with zinc oxide nanoparticles (ZnO NPs at 25, 50, and 75 mg/L) under fluorescent light (FL) or in darkness (D). The second experiment analyzed the effects of light-emitting diodes (LEDs) of variable light spectra on the formation of adventitious bulbs and their contents of phenolic acids. Spectral compositions of red (R; 100%), blue (B; 100%), red and blue (RB; 70% and 30%, respectively), a mix of RB and green (RBG) in equal proportions (50%), and white light (WLED, 33.3% warm, neutral, and cool light, proportionately) were used in the study. FL and D conditions were used as controls for light spectra. Bulbs grown in soil served as control samples. The most abundant phenolic acid was p-coumaric acid. Treatment with LED light spectra, i.e., RB, RBG, WLED, and B, translated into the highest p-coumaric acid concentration as compared with other treatments. Moreover, all the bulbs formed in light, including those grown on the media supplemented with ZnO NPs and under FL light, contained more p-coumaric acid than the bulbscales of the control bulbs grown in soil. On the other hand, control bulbs grown in soil accumulated about two to three times higher amounts of chlorogenic acid than those formed in vitro. We also found that the levels of all examined phenolics decreased under FL, R, and D conditions, while the bulblets formed in vitro under RB light showed the highest phenolic content. The use of ZnO NPs increased the content of p-coumaric, chlorogenic, and caffeic acid in the bulblets formed under FL as compared with those grown in darkness.

Lilium candidum L. is a plant with rich cultural traditions and huge potential in floriculture and modern medicine. Our study analyzed the effects of light emitting diodes (LEDs) of variable quality on adventitious organogenesis induced in bulb scales placed on Murashige and Skoog medium. In addition to the spectral compositions of red (100%), blue (100%), and red and blue light (RB ratio 7:3), RB light was mixed in equal proportions (50%) with green (RBG), yellow (RBY), UV (RBUV), and far red (RBfR) light. We also tested white LED (Wled). Fluorescent lamp light (Fl) and darkness (D) served as controls. We assessed the effects of light on the morphometric features as well as the physiological and biochemical quality of the bulblets (adventitious bulbs). Bulb formation was observed under all light qualities, even in darkness, albeit to a limited extent. White LED light (Wled) treatment translated into the highest efficiency of bulblet formation and the greatest number of bulbs with developed leaves. The leaves, even though the shortest ones, also developed as a result of RBG treatment, and this light mixture enhanced the diameter of the forming bulblets. The bulbletsunder this light spectrum accumulated the most chlorophyll and carotenoids. The bulblets formed under B, RBfR and RBG LED had more than two times higher phenoliclevels than those formed under R LED and Fl. The bulbletsformed under B LED were the richest in soluble sugars, similarly to those developing in darkness (D).

Our experiment was conducted in two stages, i.e., pretreatment (first stage) and regeneration (second stage). The first stage was carried out in a liquid Murashige and Skoog basal medium (5 µM BAP and 0.05 µM NAA) in a bioreactor with a RITA temporary immersion system under the light of a fluorescent lamp. Explants (bulbscales) were immersed in the medium once a day for 15 minutes (RITA 1×15) or three times a day for 1 (RITA 3×1), 5 (RITA 3×5), and 15 minutes (RITA 3×15) for one to six weeks. For regeneration, the explants were transferred onto a solid medium of the same composition for another six weeks. The bulbscales not exposed to the liquid medium were used as a control. Biomass weight, biomass growth index, number and percentage of dry matter of bulblets, and the content of soluble sugars in the bulblets and in the liquid medium were examined. The bulblets were formed in all combinations from the third week of the culture, and their number increased in the RITA 3×15 combination for both the first and the second stages of the experiment. After the longest, 6-week pretreatment, more bulblets were obtained than in the control. Their fresh weight after six weeks of regeneration was positively associated with extended pretreatment time. This was in contrast with the dry weight of the bulblets, which decreased in the second stage of the experiment along with the extension of its first stage. Prolonged contact of the explants with the liquid medium during the pretreatment resulted in a higher content of soluble sugars in the bulblets at both stages of the experiment. The content of soluble sugars in the liquid medium decreased over time in all tested combinations. After six weeks of bioreactor culture, the lowest level of soluble sugars was observed in the RITA 3×15 combination.