Supplementary LED Interlighting Improves Yield and Precocity of Greenhouse Tomatoes in the Mediterranean

Abstract

In Northern Europe, the use of light–emitting diodes (LEDs) is widely adopted in protected horticulture, enabling to enhance plant growth by ensuring needed radiative fluxes throughout seasons. Contrarily, the use of artificial lighting in Mediterranean greenhouse still finds limited applications. In this study, the effects of supplemental LED interlighting on vegetative development, fruit growth, yield, and fruit quality of high-wire tomato plants (Solanum lycopersicum L. cv. ‘Siranzo’) during spring and summer season were addressed in a hydroponic greenhouse in Italy. Plants were either grown under natural solar radiation (control), or by adding supplemental LED interlighting. LED treatment featured red (R) and blue (B) light (RB ratio of 3) and a photosynthetic photon flux density of 170 µmol m−2 s−1 for 16 h d−1. Supplemental LED interlighting enhanced yield as a result of increased fruit weight and dimension. While no effects on soluble solids content and fruit color at harvesting were observed, supplemental LED interlighting accelerated ripening by one week in spring and two weeks in summer and this also resulted in increased cumulated productivity (+16%) as compared to control treatment. Overall, supplemental LED interlighting can represent a feasible technology for tomato greenhouse production also in the Mediterranean region.

Supplemental LED Increases Tomato Yield in Mediterranean Semi-Closed Greenhouse

“…Considering this parameter, generally, plants grown with SL showed higher values than under NL ( Figure 6). The same results were obtained from Paucek et al [34] with supplemental LED inter-lighting. Like most growth processes, fruit development is dependent on temperature [28], and, at same time, tomato fruit are capable of photosynthesis and may contribute up 20% to the fruit photosyntate content [34].…”

“…Probably, the differences between LEDs and control treatments was higher for our experiment, because the average external cumulated solar radiation was on average 1900 J cm −2 d −1 for Paucek et al [34], while during our experiment it was 1118 J cm −2 d −1 (data not shown). So, during our experiment, the plants grown only with NL had less light available than during the experiment of Paucek et al [34]. Considering yield, 'Sorentino' was the cultivar with the highest difference between SL and NL conditions, because, as described previously, this cultivar did not differentiate branched inflorescence under NL, while, instead, this occurred for 'Juanita' and 'Solarino' with the reduced advantage of LED application (Figure 7).…”

“…Considering cumulate total yield (Figure 7), the differences between light treatments started about 60 days after the first day of SL application, and, on average, at the end of the cycle, the tomato yield was 22% higher under LEDs than without SL (Figure 7). During a similar experiment conducted in Bologna (Italy, 44 • 34 49" N, 11 • 31 54" E) from January to September with a beef tomato cultivar, plants grown with LEDs showed 16% more yield than plants grown with NL [34]. Probably, the differences between LEDs and control treatments was higher for our experiment, because the average external cumulated solar radiation was on average 1900 J cm −2 d −1 for Paucek et al [34], while during our experiment it was 1118 J cm −2 d −1 (data not shown).…”

“…During a similar experiment conducted in Bologna (Italy, 44 • 34 49" N, 11 • 31 54" E) from January to September with a beef tomato cultivar, plants grown with LEDs showed 16% more yield than plants grown with NL [34]. Probably, the differences between LEDs and control treatments was higher for our experiment, because the average external cumulated solar radiation was on average 1900 J cm −2 d −1 for Paucek et al [34], while during our experiment it was 1118 J cm −2 d −1 (data not shown). So, during our experiment, the plants grown only with NL had less light available than during the experiment of Paucek et al [34].…”

LED Lighting Strategies Affect Physiology and Resilience to Pathogens and Pests in Eggplant (Solanum melongena L.)

“…In northern latitudes, solar light levels during the winter can be insufficient to maintain production levels and product quality, due to the low light intensities and short photoperiods ( Davis and Burns, 2016 ). The potential of supplemental lighting to foster off-seasonal production in the Mediterranean region is also now under investigation ( Palmitessa et al, 2020 ; Paucek et al, 2020 ). Under low-light conditions, natural light can be supplemented by artificial lighting, with high pressure sodium (HPS) fixtures currently being the predominant greenhouse lighting source.…”