Current status of lettuce production in soilless culture: environmental conditions

Lettuce is widely cultivated as a model crop in controlled-environment agriculture and has consequently been the subject of extensive research worldwide. Recent studies have predominantly focused on the effects of light-emitting diodes (LEDs), particularly light quality, intensity, photoperiod, and direction. In response to the development of artificial lighting technologies and the growing body of related research, this review synthesizes and evaluates studies published between 2012 and 2025 on the application of LED lighting in lettuce cultivation. In addition, research published between 2017 and 2025 addressing the effects of other key environmental factors, including temperature, relative humidity, carbon dioxide concentration, and air velocity, on lettuce growth, yield, and quality is critically reviewed. By integrating findings across these environmental variables, this review provides practical insights and reference ranges for optimizing lettuce production under controlled conditions and serves as a valuable resource for researchers and producers seeking to advance controlled-environment lettuce cultivation.