On the Influence of Wavelengths of Different Ranges of Photosynthetically Active Radiation on the Carbon Isotope Composition of Plant Biomass and Its Fractions (Using as the Example Lettuce (<i>Lactuca sativa</i> L.) of the Aficion Variety)

Abstract

The influence of incident wavelengths of four ranges: short-wave red (623–641 nm), long-wave red (646–667 nm), far red (727–751 nm) and blue (452–477 nm) on the carbon isotopic composition of lettuce biomass (Lactica sativa L.) of the Aficion variety was studied. Lettuce was grown in climatic chambers, lighting was provided by irradiators based on narrow-band LEDs. Monochromatic blue and red light have the strongest multidirectional influence. Radiation from the blue range shifts the carbon isotopic composition of lettuce biomass towards enrichment in 12C. Radiation from the red range shifts the carbon isotopic composition of lettuce biomass towards enrichment in 13C. Based on the previously developed model of carbon isotope fractionation in a photosynthesizing cell, carbon isotopic shifts of plant leaf biomass were analyzed. It is shown that in the dark period the biomass is enriched in 12C. This is a consequence of dark respiration, during which the plant loses CO2 enriched in 13C. It is shown that the reason for the observed isotopic differences between the water-soluble and water-insoluble fractions of the leaf biomass is a result of the different participation of the assimilatory carbon flux, enriched in 12C, and the photorespiratory carbon flux, enriched in 13C, in the formation of these fractions during photosynthesis.