In the thesis, we performed a fumigation experiment on plants. We were interested in the exchange of carbon dioxide through the cork tissue of the trunk, which we know as trunk respiration. The concentration of CO2 in the trunk of the plant is higher than in the atmosphere due to respiration and transport of gas from the roots. We tried to measure this process in a model plant alder buckthorn (Frangula alnus). We chose this plant because of the structure of the stem (many lenticels) and because it occurs in the area of mofettes, which are characterized by high soil CO2 concentrations. In the experiment, we tested the response of trunk respiration to the increase in CO2 concentration in the soil achieved by fumigation. Different concentrations of CO2 were manually supplied to the plants from a gas cylinder. We started with a concentration of 2 L / min and continued with 5 L / min. The CO2 flow from the trunk was measured with a Mux Box measuring device, which recorded the change in concentration with an infrared gas analyser. The highest increase in CO2 concentration was measured during the fumigation with 5 L/min, what was expected. During the experiment, we encountered methodological problems. Due to unsufficient aeration of the system, while performing the experiment, the measurements of the atmospheric CO2 concentration were incorrect. Therefore, we decided to take the values of atmospheric CO2 concentration from the period before fumigation at the same time period of the day. From the obtained data, we proved that after fumigation, the exchange of CO2 from the trunk to the atmosphere increases.