Development of Tomato Plants under Illumination of Different Spectral Composition

The development of tomato plants (Solanum lycopersicum L., variety Bonsai) under illumination with various LED lamps was studied. Four illumination options—warm white (WW) as control, solar box (SB), red–green–blue (RGB), and red–blue (FS)—were used in the experiment. They were characterized by different combinations of blue (B), green (G), and red (R) proportions in the spectrum: 14% B : 48% G : 38% R (WW), 26% B : 41% G : 33% R (SB), 32% B : 19% G : 49% R (RGB), 27% B : 11% G : 62% R (FS). The photon flux density was 150 μmol quanta/(m 2 s). It was found that the difference in the R : G : B ratio in the spectra did not affect the accumulation of raw and dry mass of the aboveground parts and roots and the water and dry matter content in the green parts of plants. However, significant differences in the structure of the stomatal apparatus were found depending on the ratio of the main wavelengths (R : G : B) in the spectrum. The density of stomata distribution on the underside of the leaf was the highest in plants under WW conditions and the lowest in plants under FS conditions; the spectral composition of the latter was characterized by a decrease in the proportion of green illumination by 4 times and an increase in the proportions of red and blue illumination by almost two times. As expected, the size of stomatal guard cells was the largest in plants under FS conditions and the smallest in plants under WW conditions. The values for plants grown under RGB and SB were intermediate between minimum (WW) and maximum (FS) values. The response of plants to an increase or decrease in the proportions of the main wavelengths (R : G : B) in the spectrum in the range of 20–30% was flexible and did not affect changes in habitus but promoted acclimation to uncomfortable conditions through physiological parameters. It is concluded that a large proportion of green in the spectrum can have a certain effect on the accumulation of water and dry matter in the aboveground parts of plants and the structure of the stomatal apparatus.