Effect of Light Spectra and Photoperiod on Flowering and Biomass Accumulation in Arugula (Eruca sativa L.)

Abstract

Optimising light quality and photoperiod is a critical approach to improving crop growth, yield, and flowering in controlled-environment agriculture, where artificial lighting serves as the primary energy source for plant development. The present study evaluated the influence of different LED light spectra and photoperiods on biomass accumulation and flowering behaviour in arugula (Eruca sativa L.) cultivated under indoor farming conditions. Two cultivars, ES1 and ES2, were grown in a hydroponic production system and exposed to five lighting treatments comprising different red-to-blue and blue-to-red light ratios under 16-h and 18-h photoperiods, including a control treatment. The experiment was conducted using a factorial completely randomised design (FCRD) with three replications. Growth and reproductive responses were assessed by recording fresh leaf biomass, fresh root biomass, crop growth duration, and days to flowering. Statistical analysis revealed significant differences among light treatments, cultivars, and their interactions for all measured parameters. The 2B:1R light spectrum with a 16-h photoperiod produced the highest fresh root biomass, while the 2R:1B spectrum with a 16-h photoperiod produced the highest leaf biomass. Modified red and blue light combinations also reduced crop growth duration and promoted earlier flowering compared with the control, although the most effective treatment varied between cultivars. Overall, ES2 showed greater biomass accumulation and earlier flowering than ES1 under most optimised lighting conditions. These findings indicate that appropriate manipulation of LED light spectra and photoperiod can improve vegetative growth and reproductive development in arugula and provide useful guidance for controlled indoor production.