Growth, Development and Photosynthesis of some Horticultural Plants as Affected by Different Supplementary Lighting Technologies

New lighting technologies of interest for the greenhouse horticulture have been introduced in the market during the last couple of years. The LED-technology has attended special interest from researchers and business, with attractive features such as long lifetime, high efficiency and possibilities for tailoring the light spectrum. In this study, common horticultural crops were grown in greenhouse conditions using different LED-light sources as well as HPS-lamps for supplementary lighting. Experiments were conducted both during increasing (spring) and decreasing (fall) natural light conditions. Biometric as well as photosynthetic evaluation of plant performance was performed. Plant parameters such as internodal length, development of flowers and lateral shoots, biomass accumulation (fresh/dry weight) and developmental time were recorded, in addition to photosynthesis and stomata conductance. Results indicate that biomass production was the highest when HPS-light was used. For photosynthesis and stomata conductance there were no differences with respect to the different treatments. Plant morphology was affected, with a reduction in stem elongation when red/blue or white LEDs were used as light source in ornamental plants grown during autumn period, and development was also delayed when LEDs were applied. However, in experiments performed during springtime there were no differences in plant morphology related to the different light sources.