1 October 2019 | Volume 10 | Article 1305 ORIGINAL RESEARCH doi: 10.3389/fpls.2019.01305 published: 30 October 2019 Frontiers in Plant Science | www.frontiersin.org 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 Youssef Rouphael 1 *, Spyridon A. Petropoulos 2 , Christophe El-Nakhel 1 , Antonio Pannico 1 , Marios C. Kyriacou 3 , Maria Giordano 1 , Antonio Dario Troise 1 , Paola Vitaglione 1 and Stefania De Pascale 1 * 1 Department of Agricultural Sciences, University of Naples Federico II, Portici, Italy, 2 Department of Agriculture, Crop Production and Rural Environment, University of Thessaly, Volos, Greece, 3 Department of Vegetable Crops, Agricultural Research Institute, Nicosia, Cyprus 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 effcient 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 effciency 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 profle under optimal light conditions. The main detected carotenoids were β-cryptoxanthin and violaxanthin+neoxanthin, followed by lutein and β-carotene. All the Edited by: Thomas Graham, University of Guelph, Canada Reviewed by: Christine Becker, Hochschule Geisenheim University, Germany Ki-Ho Son, Gyeongnam National University of Science and Technology, South Korea *Correspondence: Youssef Rouphael youssef.rouphael@unina.it Stefania De Pascale depascal@unina.it Specialty section: This article was submitted to Plant Abiotic Stress, a section of the journal Frontiers in Plant Science Received: 27 April 2019 Accepted: 19 September 2019 Published: 30 October 2019 Citation: Rouphael Y, Petropoulos SA, El-Nakhel C, Pannico A, Kyriacou MC, Giordano M, Troise AD, Vitaglione P and De Pascale S (2019) 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. Front. Plant Sci. 10:1305. doi: 10.3389/fpls.2019.01305