$^{13}$С/$^{12}$С carbon isotope fractionation between atmospheric carbon dioxide and photosynthesis products in plant leaves as affected by the spectral composition of lighting environment

We have studied influence of the light with various spectral characteristics, coming to plants during its growth, on the distribution of carbon isotopes between atmospheric carbon dioxide and the primary products of photosynthesis in plant leaves, using the developed set of methods and laboratory setups. The difference between the carbon isotopic composition in the air near the plants and in their leaves varies from 7 to 19 ${}^0\!/_{\!00}$, increase in the red component of the spectrum resulting in leave enrichment with light carbon isotope 12C. This difference reflects the degree of isotope fractionation during the plant life, characterizes the rate of carbon assimilation due to photosynthetic reactions, and can be used as a phytomonitoring parameter.