ASSESSMENT OF THE CONTRIBUTION OF ROOT CARBON NUTRITION TO THE FORMATION OF PLANT BIOMASS IN A MODEL EXPERIMENT

The study of mechanisms of carbon dioxide transformation in agroecosystems from the position of ideas about CO2 absorption exclusively by chlorophyll-containing parts of vegetative plants does not allow to objectively evaluate the ecosystem role of each component. To evaluate the contribution of root carbon nutrition to the formation of plant biomass, a model experiment was laid down using the author’s device, which allows isolating the root and leaf parts of the plant from each other and recording the CO2 values to calculate its balance. A paulownia seedling (Paulownia tomentosa (Thuns.) Steud., 1841) with a known initial mass, vegetating under a 12-hour light regime, was used as an experimental plant. The contribution of root carbon nutrition to biomass formation was calculated from the difference in C-CO2 in the leaf chamber atmosphere and the content of elemental carbon in the plant at the end of the experiment. The carbon content in plant parts was determined on a MultiEA 200CS carbon analyzer at a temperature of 1100 °C. As a result of 30 days of observations, it was found that the mass of C-CO2, which was present throughout the experiment (6960 ppm) in the atmosphere of the leaf chamber with a volume of 0.06 m3, corresponded to 210 mg of carbon. At the same time, the carbon content in the incremented mass of the seedling (690 mg) in absolutely dry form contained 274.9 mg of elemental carbon, which indicates the presence of another alternative source of carbon supply. According to the authors, 64.9 mg of elemental carbon (23.6 % of the total mass), which went to the formation of the incremented biomass of the experimental plant, came through the root system. The obtained results allow us to explain cases when forest areas can form a balance shifted towards the CO2 flow. An idea of the mechanism of root carbon of plants and its potential allows us to more accurately create models of CO2 transformation in soil-plant systems.