Effect of supplementary red and blue LED interlighting on greenhouse-grown tomatoes during spring season in the Mediterranean

In recent years, light emitting diodes (LEDs) have experienced a wide increase in their employment for protected horticulture in Northern Europe, offering the possibility to enhance plant growth under controlled environmental facilities. Light is an important source of energy for plant development and, therefore, the lack of a proper supply of sunlight can be a drawback which can lead to a decrease in the plant yield. Supplemental LED interlighting can prevent light shortage by providing plants with the needed radiative fluxes. In this study, the effects of supplemental LED interlighting on vegetative growth, fruit growth, yield, fruit quality and physiological traits of high-wire tomato plants (Solanum lycopersicum ‘Siranzo’) during the spring season were addressed. Tomato plants were grown under hydroponic conditions in an environmentally controlled commercial greenhouse. Two treatments were applied, including a control relying on solar radiation only and an illuminated treatment, where plants were supplied with supplementary LED interlighting system consisting of blue and red diodes (RB ratio of 3), whose peak wavelength were 465 and 669 nm, respectively. Interlighting lamps were placed at 2 m height within the canopy and supplied 170 µmol m-2 s-1 light at 30 cm distance from the lamp for 16 h day-1. Weekly measurements highlighted greater vegetative and fruit growth, yield and physiological parameters when supplementary lighting was provided. The research explores the sustainability of supplemental LED interlighting in Mediterranean high-tech greenhouse tomato production.