Influence of external factors on the behavior of CO2 in the root system of plants in a model experiment

Abstract Currently, the mechanism of root uptake of carbon dioxide (CO 2 ) by plants and the factors influencing it are poorly understood in the scientific literature. The aim of the work was to establish the influence of external factors on the emission and absorption of CO 2 by the roots and leafs of experimental plants. The research was carried out using the author's installation of vertically differentiated accounting of CO 2 fluxes in the soil–plant-atmosphere system, equipped with CO 2 sensors in hermetically isolated leaf and root chambers. Maize plants in the amount of 19 pieces were used as the object. The model experiment lasted for 40 days, in which four different modes (A-D) were studied, reflecting the influence of external factors on the carbon nutrition of plants. In the “A” mode, the pattern of changes in leaf and root CO 2 absorption was studied depending on the light regime. An inverse correlation (r = -0.859) was established between the dynamics of CO 2 concentrations in the leaf and root chambers during the change of the light phase (16 h) to the night phase (8 h), which allows us to consider the mechanism of root carbon nutrition as an alternative source of CO 2 nutrition for plants. It was also found that the mechanism of root CO 2 absorption is activated in the light phase when the atmospheric CO 2 concentration reaches 417–367 ppm. In the “B” mode, a model of transformation of carbon nutrition of plants using nitrogen fertilizers was considered. It was found that in the first 3 days, fertilizing with ammonium nitrate leads to increased respiration of leaves at night and to a decrease in absorption capacity during the daytime. The absorption capacity of the leaves is reduced from 70.4 ppm to 92.3 ppm, compared with the indicator of mode “A”. In the “C” mode, the effect of different levels of illumination intensity on the carbon nutrition of plants was studied. With a twofold increase in illumination intensity (from 1750 to 3500 lx), after the transition to the dark phase, there is a delay in response (the beginning of leaf respiration) for 80 min. In the “D” mode, the behavior of the root carbon nutrition of plants is studied with a possible increase in CO 2 in the atmosphere, for example, with an increase in the intensity of soil respiration. It was found that as the concentration of CO 2 in the atmosphere of the leaf chamber increases (500–1500 ppm), its absorption by the root system stops.