Photosynthetic characteristics and growth performance of lettuce (Lactuca sativa L.) under different light/dark cycles in mini plant factories

Abstract

We investigated the photosynthesis and growth of lettuce (Lactuca sativa L.) grown under three light/dark cycles in a mini plant factory with artificial illumination. A relative longer light cycle [12/12 h (light/dark)] increased not only light-response curve parameters, such as light-saturated net photosynthetic rate, light-saturation point, light-compensation point, dark respiration rate, but also upregulated CO2-response curves parameters, such as CO2-saturated net photosynthetic rate, initial carboxylation efficiency, and photorespiration rate, compared to those of the shorter light cycles [6/6 h and 3/3 h (light/dark)]. A longer light cycle enhanced electron transfer potential, increased the chlorophyll amount, leaf area, and biomass and reduced the root/shoot ratio and the specific leaf area. Our results imply that the prolonged light cycle led to the increase in photosynthetic capacity and significantly enhanced the growth rate of lettuce.