Cultivar-Specific Performance and Qualitative Descriptors for Butterhead Salanova Lettuce Produced in Closed Soilless Cultivation as a Candidate Salad Crop for Human Life Support in Space

Abstract

Plant production is crucial for space journeys self-autonomy by contributing to the dietary intake necessary to sustain the physical and psychological well-being of space colonists, as well as for contributing to atmospheric revitalization, water purification and waste product recycling. Choosing the appropriate cultivar is equally important as the species selection, since cultivar influences the obtained fresh biomass, water use efficiency (WUE), growing cycle duration, qualitative features and postharvest performance. Two differently pigmented butterhead Lactuca sativa L. (red and green Salanova) cultivars were assessed in terms of morphometric, mineral, bioactive and physiological parameters. The experiment was carried out in a controlled environment growth chamber using a closed soilless system (nutrient film technique). Red Salanova registered a biomass of 130 g at harvest, which was 22.1% greater than green Salanova, and a water uptake of 1.42 L during the full growing period corresponding to WUE of 91.9 g L–1, which was 13.8% higher than that of green Salanova. At harvest, green Salanova had accumulated more P, K, Ca, Mg and 37.2% more nitrate than red Salanova, which however had higher relative water content, leaf total and osmotic potential and higher SPAD index. Red Salanova also exhibited at harvest around two-fold higher lipophilic antioxidant activity and total phenols, and around six-fold higher total ascorbic acid levels. These latter characteristics improved the antioxidant capacity of red Salanova enabling it to use light more efficiently and deliver better overall performance and yield than green Salanova. Moreover, the higher phenolics and total ascorbic acid contents of red Salanova constitute natural sources of antioxidants for enriching the human diet and render it an optimal candidate cultivar for near-term missions.

Variation in Macronutrient Content, Phytochemical Constitution and In Vitro Antioxidant Capacity of Green and Red Butterhead Lettuce Dictated by Different Developmental Stages of Harvest Maturity

“…The non-destructive measurements of chlorophyll content (SPAD Index) [30] measured by El-nakhel et al [31], reflected the changes obtained regarding chlorophyll pigment measurements in our work. Indeed, chlorophyll increased significantly with lettuce maturation, and in both harvest stages was significantly higher in red Salanova, which was the exact same trend observed with chlorophyll measurements of lettuce at 4 and 19 DAT [31]. In photosynthetic tissues, carotenoids, and chlorophylls a and b operate in light harvesting and perform tasks in photo-protection by quenching free radicals, singlet oxygen, and other reactive species [30].…”

“…In the current study, the loading matrix indicates that variation in lutein and β-carotene was most closely aligned with total chlorophyll, whereas variation in nitrate was not correlated with total polyphenol content ( Figure 2). The effectiveness of PCA in interpreting species/cultivars differences across several functional quality attributes in response to a wide range of preharvest factors such as the genetic material, the maturity stage, environmental conditions and agricultural practices have been reported previously by several researchers [5,6,9,31]. This was also the case of this study conducted under fully controlled conditions, since the score plot of PCA integrated information about the nutritional and functional profile of the red and green-pigmented lettuce harvested at microgreens or at mature stage (Figures 2 and 3).…”

“…Ascorbic acid is a potent dietary water-soluble antioxidant, and like most vitamins, is not synthesized by humans, unlike animals and plants, therefore its input from exogenous sources is a requirement. A diet containing fruits and vegetables helps in procuring this vitamin [36,37], and leafy vegetables account for a significant input [31]. It notably diminishes the hostile effect of reactive nitrogen and oxygen species, scavenges free radicals in our body and has anti-carcinogenic and immunomodulatory effects.…”

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

“…In addition, leaf pigmentation significantly correlates to the constitution and concentration of phenolic compounds belonging mainly in the subgroups of phenolic acids, flavonoids, and anthocyanins [14]. 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].…”

Potatoes as a Crop for Space Life Support: Effect of CO2, Irradiance, and Photoperiod on Leaf Photosynthesis and Stomatal Conductance

“…A range of crops have been suggested for space life support systems, including leafy greens and vegetables as supplemental foods for early missions (Tibbitts and Alford, 1982;Massa et al, 2015;El-Nakhel et al, 2019), as well as staple type grains, legumes, and tuberous crops for more full nutrition on future missions (Tibbitts and Alford, 1982;Waters et al, 2002;Wheeler, 2017). A species found on many of these crop lists is potato, Solanum tuberosum L. (Tibbitts and Alford, 1982;.…”