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.

Keywords

• biomass accumulation
• chlorophyll fluorescence
• leaf gas exchange
• morphogenesis
• photoperiod