CULTIVATION OF VEGETABLE TRANSPLANTS USING SOLID-STATE LAMPS FOR THE SHORT-WAVELENGTH SUPPLEMENTARY LIGHTING IN GREENHOUSES

The objective of studies was to compare cultivation of greenhouse vegetable transplants under short-wavelength solid-state lamps developed for supplementation of high-pressure sodium (HPS) lamps used in greenhouses. Four types of solid-state lamps were made using advanced light-emitting diodes (LEDs) with peak emissions at 455, 470, 505, and 530 nm, and were installed in a greenhouse. The generated photosynthetic photon flux density of each type of solid-state lamps was 15 μmol∙m^-2∙s^-1 and the photosynthetic photon flux density of HPS lamps was 90 μmol∙m^-2∙s^-1. Transplants of cucumber hybrid ‘Mirabelle’ F₁, tomato hybrid ‘Magnus’ F₁ and sweet pepper variety ‘Reda’ were grown in greenhouse of phytotron complex under illumination of HPS lamps and with supplementation by emission of solid-state lamps. The reference transplants were grown under illumination of HPS lamps (110 μmol∙m^-2∙s^-1). During transplants cultivation photoperiod was maintained at 18 h, the day/night temperature was 20-23/15-18°C and relative air humidity was 50-60%. Measurements of growth parameters and photosynthetic pigments were performed at the end of the experiment. Our investigations revealed that the effect of supplementary 455, 470 and 505 nm LED illumination with high pressure sodium lamps increased leaf area, fresh and dry weight and photosynthetic pigments content of all vegetable transplants. Meanwhile, supplemental 530 nm LED illumination had positive effect on development and photosynthetic pigments accumulation of cucumber transplants only. Such illumination had no effect on the growth and development of tomato and sweet pepper transplants.