Influence of light quality on leaf physiology of sweet pepper plants grown under drought

The application of artificial light to improve crop production in greenhouses is widely used in the horticultural sector. In this study, we evaluated the impact of light quality on sweet pepper plants’ physiology during a period of water deficit. Pepper plants were cultivated in a climate chamber and exposed to three different light regimes; (compact fluorescent lamps [CFL], continuous intensity from light emitting diodes [LED] [LEDcont] and bell-like shape illumination schedule from LEDs [LEDday]). The effect of temporary water shortage under these light treatments on plant height, chlorophyll and proline concentration, the maximum efficiency of photosystem II (Fv/Fm), the electron transport rate (ETR), and the non-photochemical quenching (NPQ), were studied. In general, plants exposed to CFL showed higher growth rates as compared to those exposed to LED under well-watered conditions. However, the lighting source did not induce significant effects on plant growth and chlorophyll concentration during water deficit, even though proline concentration was higher in plants exposed to CFL and to drought when compared to those exposed to LEDcont and LEDday. LED radiation led to a higher ETR and an early onset of NPQ under water deficit, suggesting an activation of the cyclic electron transport. As outcome, plants grown under LEDcont showed the highest photochemical performance. Overall, the results suggest that pepper plants grown under CFL radiation perform better, even under water deficit, possibly due to the more balanced light spectrum.