A comparison of growth and photosynthetic characteristics of lettuce grown under red and blue light-emitting diodes (LEDs) with and without supplemental green LEDs

Plants could be an important aspect of future space missions. Lighting systems for plant growth chambers will need to be lightweight, reliable, and durable, and light-emitting diodes (LEDs) have these characteristics. Previous studies demonstrated the combination of red and blue LEDs as an effective light source for several crops. The addition of green supplemental lighting offers a psychological benefit for the crew, since most plant leaves would appear green and normal similar to a natural setting under white light. The addition of green light could offer more benefits, since green light can better penetrate the plant canopy and potentially increase plant growth by increasing photosynthesis from the lower canopy leaves. In this study, lettuce plants grown under red and blue LEDs were compared to plants given an additional 5 % (6 μmol m-2 s-1) of green light. Light and CO2 photosynthesis response curves were measured along with other physiological parameters, and there was no significant difference between the treatments. Future studies will examine higher levels of supplemental green light. The use of green light would be beneficial, since it did not impact plant growth, it provides useful photosynthetically active radiation once it is absorbed, and the plants would appear green and healthy to the crews on space mission.