Dynamic regulation of photosynthetic processes under variable spectral LED irradiation of plants

Abstract

In natural conditions of plant growth, along with changes in the intensity of light during different periods of time, there is a change in the spectral composition of the incident radiation. The ratio between the blue and red spectral regions changes from 0.50 for direct radiation of the sun, to 0.95 for diffuse solar radiation, depending on the height of the sun and the time of day. The work investigated the effect of light of different spectral composition on the functional characteristics of the photosynthetic apparatus of potato plants (Solanum tuberosum L.) of the Zhukovsky Early variety, grown by aeroponics in two vegetation chambers of a phytotron using LEDs sources with preferential irradiation of plants with blue light (LEDs BL, max = 470 nm) or red light (LEDs RL, λ max = 660 nm) of the spectral range of photosynthetically active radiation (PAR). With a total PAR intensity of 400±28 μmol Ł m 2 Ł s 1 , the proportion of blue light was 293.6 μmol Ł m 2 Ł s 1 (chamber 1), and of red light it was 262.0 μmol Ł m 2 Ł s 1 (chamber 2). As a result, the ratio BL/RL (when comparing the intensities of radiation in the two chambers of the phytotron) was about 0.7. The measurements were carried out on plants grown for a long time under irradiation in the PAR rang with the predominant blue (PAR + BL) or red light (PAR + RL). The dynamics of photosynthetic indexes were investigated 0, 1, 2, and 3 hours after the light regime changed from PAR + RL to PAR + BL or from PAR + BL to PAR + RL. When plants were irradiated with a larger share of the red light PAR spectrum (PAR + RL), a lower rate of photosynthesis was observed compared to plants grown with PAR + BL, both at 400 μmol Ł m 2 Ł s 1 and at saturating light intensity (1200 μmol Ł m 2 Ł s 1 ). A change in the PAR + RL spectral mode for PAR + BL resulted in an increase in the rate of photosynthesis, a slight increase in the effective quantum yield and non-photochemical quenching. When the light mode changed from PAR + BL to PAR + RL, photosynthesis rate, electron transport speed, non-photochemical quenching decreased compared to plants irradiated with PAR + BL, but no change was observed in the maximum and effective quantum yield. The specific effects of blue and red light on the activity of light reactions in photosynthesis and the rate of photosynthesis in changing spectral composition after long-term plant exposure to environmental factors, which we detected for the first time in this work, make it possible to better understand the nature of plant adaptation in natural growth conditions. In plant growing with LED lighting, this allows directional use of LED emitters of different spectral composition, given the duration of predominantly blue or red irradiation.