Experiments were carried out at the Lithuanian Research Centre for Agriculture and Forestry Institute at the phytotron complex of Plant physiology laboratory. The objective of our studies was to explore the blue and red components of the spectrum of effects on cucumber transplant cultivation. Cucumber hybrid 'Mandy' F1 was used for investigation. Day/night temperature till germination was 25 °C, and a 14-h photoperiod was maintained. Cucumber seedlings were irradiated with solid-state lighting complex of modules consisting of a 638 nm red (R), as supplemented by blue 445 nm (B), red 669 nm (R669), far red 731 nm (FR) light: R, R + B; R + R669 + B, R + R669 + FR, R + R669 + TR + B. The total photosynthetic photon flux density was 200 micromole cm-2 s-1. Our investigations revealed that irradiation with red light of solid-state light is not enough for cucumber transplant cultivation. Under the modules, which are designed only for the red (R) and far-red part of the spectrum (R + R669 + FR) light-emitting diodes (LEDs), cucumber transplants were elongated and had the least number of leaves, the leaf area was also the least one, fresh / dry weight was minimal and there was established significantly lower amount of photosynthetic pigments. There was very low chlorophyll a and b ratio their leaves. The addition of a combination of blue LEDs 445 nm LED (R + B, R + B + R669, R669 + R + FR + B) shows that under these modules seedling hypocotyls were more than twice as short, formed twice as many leaves, their leaf area was seven times higher, and they accumulated more photosynthetic pigments. [ABSTRACT FROM AUTHOR]