The influence of light emitted by light-emitting diodes (LEDs) of different spectral composition towards white fluorescent light FL (W) on the photosynthetic activity of leaves and yield of lettuce was evaluated in pot experiments conducted in controlled conditions at PPFD of 200 µmol m^-2 s^-1. The LEDs emitting white (12W), red (12R) and red-blue (R/B) radiation from lamps of different ratio of red diodes (R) towards the blue ones (B) (9R+3B; 10R+2B; 11R+1B) was used. The results showed that the lowest yield was found in plants grown under LED (12W), and the highest one under FL (W) light. The mass and leaf area of plants illuminated by FL (W) and LED (12R) were similar. The increase of radiation R and decrease of B caused an increase in biomass, leaf area (LA), and specific leaf area (SLA) decrease of chlorophyll concentrations in leaves. Leaves of plants cultivated under LED (R/B) had the higher stomatal conductance, photosynthesis and transpiration parameters than under other treatments. The lowest value of chlorophyll fluorescence parameters (Fo, Fm, Fv/Fm) were noted under the LED (12R) lighting. However, taking into account the energy consumption by the using light sources, the plant yielding, and other determined parameters, the most beneficial for lettuce production seems to be LED (11R + 1B) light. Taking into account the energy consumption of light sources, the plant yielding, and other determined in the study parameters, LED (11R + 1B) light appears the most beneficial for lettuce production.

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