The objective of the study was to examine the influence of supplemental lighting with sodium light and LED on leaf gas exchange and growth of tomato transplants. During cultivation period (September - October) the transplants received supplemental artificial lighting provided by standard high-pressure sodium lamps (HPS) or high-power solid-state lighting modules with red, blue and far-red LEDs. Quantum irradiance in both combinations was maintained at the same level. The third group of plants (control combination) was grown under the natural light (without supplemental lighting). The following measurements were taken: leaf gas exchange (net photosynthesis and transpiration rate) and selected morphological parameters (fresh weight of plant organs, leaf surface area, plant height). The results showed that supplemental illumination using LED or HPS light sources affected growth and physiological responses of tomato plants. The higher rates of leaf gas exchange were found in the plants supplementary lighted (compared to the control ones). Supplemental lighting also resulted in enhanced plant growth, however no significant differences were found between the plants lighted with HPS or LED. The obtained results showed that HPS lamps can be replaced by LEDs in greenhouse lighting systems for tomato transplant production during periods with insufficient natural light. ...
