LED lighting as an effective tool for regulating plant morphogenesis

The results of studying the effect of light with different spectral composition on the morphogenesis of wild-type of Arabidopsis thaliana (Col 0), as well as wei8-1tar1-1 and ahk2 mutants with modified signal transduction processes of auxins and cytokinins. We used a specially developed technique that simplifies the assessment of the effect of light on the growth and development of A. thaliana plants, especially the configuration of their root system during the entire growing season. Luminescent (LL) and light-emitting diode (LED) light sources were used, which made it possible to vary the physiologically significant blue (B), green (G), red (R), and far red (FR) spectral ranges. The R/B ratio was equal to 1 and 4 for LED 1 and LED 2 lighting options, respectively, at the same total flux density of B and R light photons. The ratios of R/FR and B/G in the spectra of LED illumination varied in the ranges closest to those observed in natural conditions. The most effective for the formation of the root system, rosette of leaves and inflorescences of A. thaliana (Col 0) was LED illumination with R/B = 4, B/G = 1 and R/FR = 6. The obtained data indicate an important role of AHK2 histidine kinase receptors in stimulation of the formation of vegetative organs of A. thaliana in response to an increase in the level of R and a decrease in B light (an increase in the R/B ratio) in complex spectral compositions. At the same time, LED lighting with a higher level of B and a low level of R light (R/B = 1, B/G = 2 and R/FR = 3) rather effectively stimulated the accumulation of the dry mass of the root system and the formation of inflorescences compared to fluorescent lighting. Stimulation of root growth by light of this spectral composition is probably mediated by a significant increase in the level of endogenous auxins. The decrease in the R/FR ratio in the spectrum of LED sources compared to the fluorescent lamp contributed to the stimulation of flowering of A. thaliana, regardless of the nature of the mutation and despite other differences in the spectral composition.