Carbon dioxide enrichment promoted the growth, yield, and light‐use efficiency of lettuce in a plant factory with artificial lighting

Lettuce (Latuca sativa L.) is a commercially important crop and a good candidate for production in a plant factory with artificial lighting (PFAL). To explore the influence of CO2 enrichment (eCO2) on lettuce growth, light‐use efficiency (LUE) and various aspects of the growth indicators were specifically assessed. Three CO2 concentrations ([CO2]): ambient CO2 (as the control, approximately 400 μmol mol−1), approximately double the ambient (DA‐CO2, 800 ± 50 μmol mol−1), and approximately quadruple the ambient (QA‐CO2, 1600 ± 50 μmol mol−1) were applied for 30 d. The results indicated that plant height, stem diameter, number of leaves, root length, leaf width, and maximum leaf area were all positively related to [CO2], which illustrated that growth was greater in the treatments with eCO2 than under ambient CO2. The daily average assimilation rate (DAAR), the average dry weight growth rate (GRdw), and yield were also greater for plants grown under DA‐CO2 and QA‐CO2 than under ambient CO2 (DAAR increased by 25.45% and 42.27%, GRdw increased by 28.76 and 37.55%, and yield increased by 33.65 and 44.16%, respectively). Light‐use efficiency increased by 28.51 and 41.12% for DA‐CO2 and QA‐CO2 compared with ambient CO2, respectively. We concluded that eCO2 has the potential to enhance production as well as light utilization in PFAL. Core Ideas Double and quadruple the ambient CO2 promoted morphogenesis, growth rate, and yield in lettuce. CO2 enrichment significantly increased the biomass accumulation of lettuce. CO2 enrichment improved the light‐energy use efficiency in lettuce.