Determining optimal cultivars and lighting conditions for teen-leaf lettuce in protected cultivation (Controlled Environment Agriculture, CEA) is critical to support the growing leafy greens industry segment. Teen-leaf lettuce is considered to be more mature than baby-leaf and less mature than head lettuce. It is typically harvested at 24-30 days. As teen-leaf lettuce is a relatively new part of the leafy greens industry segment, foundational research into environmental conditions and cultivars is currently lacking. The objective of this experiment is to observe a diverse set of lettuce cultivars growth in response to light intensity. This study provides insight into how different lettuce cultivars respond to varied light intensities and also highlights phenotypic traits to be evaluated to potentially further improve CEA-grown lettuce. Eight cultivars (Azirka, Danstar, Gladius, Ilema, Klee, Muir, Oscarade, Volcana) representing seven lettuce ‘sub-types’ (Crunchleaf, Romaine, Lollo, Salanova, Batavia, Oakleaf, Bibb) were evaluated under two different lighting conditions low DLI (targeting 10 mol m⁻² d⁻¹) and high DLI (targeting 20 mol m⁻² d⁻¹). Fourteen day old seedlings were planted in Deep Water Culture (DWC) systems with three repeated blocks under each lighting treatment. Seedlings were grown in the systems for an additional 21 days. Weekly destructive harvests took place between days 14 and 35 to establish growth curves for several measured parameters: fresh mass, dry weight, leaf count, growth index, and plant diameter for each plant. Cultivars Danstar and Muir had significantly higher fresh weight when grown under the higher light treatment. Higher light also significantly increased dry weight regardless of cultivar, however dry mass responsiveness varied between cultivars. Cultivars Danstar, Gladius, Muir, and Oscarade exhibited significantly higher dry weight when grown under the higher light treatment. Leaf number was not significantly affected by light, except for cultivar Ilema which had significantly more leaves when grown under the higher lighting treatment. The findings of this study provide insight into which cultivars are more shade tolerant and which are better suited for CEA production. Future research will further investigate the phenotypic traits present in these cultivars and identifying anatomical traits (such as stomatal density) that may be associated with higher crop performance, guiding future breeding efforts.
