Effects of Different Spectra of Supplemental Lighting on Water Use Efficiency of Lettuce Lactuca sativa L. 'Cherokee' in the Greenhouse

Successful plant production depends on providing adequate environmental conditions for plant growth. In low-light environments, growth and development of greenhouse (GH)-grown vegetables is enhanced by use of supplemental lighting (SL), which helps to increase the total daily light integral (DLI) that plants receive. Studies have examined growth and morphological responses of different vegetables using light-emitting diodes (LEDs) as SL sources. However, the effect of LED SL on water uptake has not been determined. Since physiological changes in response to differences in light spectra have been reported, light spectra from SL may play a key role regulating water relations in plants by inducing changes in stomatal conductance and transpiration. The objective of this study is to quantify growth, leaf gas-exchange responses, and water requirements of lettuce (Lactuca sativa L. ‘Cherokee’) plants grown under one of five SL treatments. A variant solar DLI will occur naturally for all treatments, and a constant DLI of 2.6 mol·m‒2·d‒1 will be provided to all plants receiving SL. Plants will be grown in a glass-glazed GH for 3 weeks and water applications will be monitored based on the available water in each container. Results from this experiment reflecting growth, water requirement and gas exchange will be presented.