LED lighting affected the growth and metabolism of eggplant and tomato transplants in a greenhouse

Light-emitting diodes (LEDs) were used for the spring greenhouse cultivation of eggplant (Solanum melongena L.) ‘Milar F1’ and tomato (S. lycopersicon L.) ‘Benito F1’ transplants. Seedlings were grown under natural light conditions with the supplemental LED light. A 16-h photoperiod provided plants with a DLI of 12.6 (eggplant) and 9.6 (tomato) mol m2/day. Four supplemental light spectra were tested: L1 (90% red + 10% blue); L2 (80% red + 20% blue); L3 (43% red + 42% blue+15% green) and L4 (56% red + 26% blue + 15% green + 3% UV-A). The PPFD in each LED light treatment was 150 ± 20 µmol/m2·s. Compared to the control plants (without LED lighting), the eggplant transplants had about a 25% larger leaf area and a higher level of total phenol content as well as a higher antiradical scavenging activity under the L1 spectrum. The favourable spectrum for the tomato transplants consisted of red to blue in a ratio of 1 : 1 mixed with a green light (L3) – the leaves were characterised by a higher content of dry matter, soluble sugars, photosynthetic pigments and total phenols; also the radical scavenging activity increased in comparison to the control group. It was shown that the supplemental irradiation of transplants was economically acceptable.