Reducing Energy Requirements in Future Bioregenerative Life Support Systems (BLSSs): Performance and Bioactive Composition of Diverse Lettuce Genotypes Grown Under Optimal and Suboptimal Light Conditions

Abstract

Space farming for fresh food production is essential for sustaining long-duration space missions and supporting human life in space colonies. However, several obstacles need to be overcome including abnormal light conditions and energy limitations in maintaining Bioregenerative Life Support Systems (BLSSs). The aim of the present study was to evaluate six lettuce cultivars (baby Romaine, green Salanova, Lollo verde, Lollo rossa, red oak leaf and red Salanova) of different types and pigmentations under optimal and suboptimal light intensity and to identify the most promising candidates for BLSSs. Baby Romaine performed better than the rest of the tested cultivars under suboptimal light intensity, demonstrating a more efficient light-harvesting mechanism. Stomatal resistance increased under suboptimal light conditions, especially in the case of Lollo verde and red oak leaf cultivars, indicating stress conditions, whereas intrinsic water-use efficiency was the highest in baby Romaine and red oak leaf cultivars regardless of light regime. Nitrate content increased under suboptimal light intensity, especially in the cultivars green Salanova and Lollo verde, while P and Ca accumulation trends were also observed in baby Romaine and Lollo verde cultivars, respectively. Chicoric acid was the major detected phenolic acid in the hydroxycinnamic derivatives sub-class, followed by chlorogenic, caffeoyl-tartaric and caffeoyl-meso-tartaric acids. Chicoric and total hydroxycinnamic acids were not affected by light intensity, whereas the rest of the detected phenolic compounds showed a varied response to light intensity. Regarding cultivar response, red oak leaf exhibited the highest content in chicoric acid and total hydroxycinnamic acids content under suboptimal light intensity, whereas red Salanova exhibited the highest hydroxycinnamic derivatives profile under optimal light conditions. The main detected carotenoids were β-cryptoxanthin and violaxanthin+neoxanthin, followed by lutein and β-carotene. All the target carotenoids decreased significantly under low light intensity, while red Salanova maintained a distinct carotenoids profile. Overall, cultivation of assorted lettuce cultivars is the optimal scenario for space farming, where baby Romaine could provide adequate amounts of fresh biomass owing to its high light-use efficiency while red oak leaf and red Salanova could contribute to the daily dietary requirements for health-promoting bioactive compounds such as polyphenols and carotenoids.

Grown to Be Blue—Antioxidant Properties and Health Effects of Colored Vegetables. Part II: Leafy, Fruit, and Other Vegetables

“…Chicoric, caffeic, and chlorogenic acids and their derivatives are the most abundant phenolic acids present in lettuce, whereas the most outstanding flavonoids include anthocyanins, quercetin, kaempferol, and flavone luteolin [35,[45][46][47]. Several authors reported a higher total phenolic content in red butterhead, red leaf and red romaine lettuces compared to their green counterparts [16,35,[48][49][50][51]. The red color of lettuce has been associated with a higher total phenolics content, known to impart a greater antioxidant activity than vitamins C and E [52], and has been attributed primarily to anthocyanins, an important group of flavonoids responsible for the red/purple coloration [53].…”

The Evaluation of Growth Performance, Photosynthetic Capacity, and Primary and Secondary Metabolite Content of Leaf Lettuce Grown under Limited Irradiation of Blue and Red LED Light in an Urban Plant Factory

“…Previously, Urrestarazu et al [19] stated that leaf lettuce showed high energy efficiency and sufficient morphological response when grown under very low light (e.g., 85 µmol m −2 s −1 ) irradiation; therefore, lettuce may be considered a low-light-adapted crop species [20]. A recent report by Rouphael et al [21] stated that lettuce growth parameters were accelerated when grown under more intense light (420 µmol m −2 s −1 ) compared to lower light irradiation (210 µmol m −2 s −1 ), and, at the same time, that bioactive compounds and mineral contents were increased under lower light irradiation compared to higher levels. Under a low light regime, the plant tends to accumulate micronutrients in its sink, resulting in lower plant growth rates as well as lower biomass accumulation.…”

“…Plant production in plant factories under different combinations of BR light under a higher light regime has been well studied, and extensive research reports have already been published [15,21]. However, achieving a sustainable food-energy nexus through the reduction of lighting energy expenses by using low levels of light irradiation while maintaining effective production is of great interest for urban plant factory systems [22].…”

The Metabolic Reprogramming Induced by Sub-Optimal Nutritional and Light Inputs in Soilless Cultivated Green and Red Butterhead Lettuce

“…Plants were located in a growth chamber equipped with high pressure sodium (HPS) lamps using the Nutrient Film Technique. Experimental set-up conditions were as previously described [ 26 , 50 ]. Briefly, plants grew in with a density of 15.5 plants per square meter, with a 12 h light−12 h dark photoperiod.…”

“…The macroelements of the FS solution were: 9.0 mM nitrate, 2.0 mM sulfate, 4.0 mM phosphorus, 4.0 mM calcium, 1.0 mM magnesium, and 1 mM ammonium. The factor light had two levels (experiment 2), namely optimal light (OL), with a photosynthetic photon flux density (PPFD) of 420 μmoL m −2 s −1 and low light (LL), with a PPFD of 210 μmoL m −2 s −1 [ 50 ]. In both experiments, all treatments were replicated three times.…”