43.1 billion tons of CO2 were released into the atmosphere by human activities in 2019. Thus, in April 2022, the global CO2 concentration was 421 ppm. Increasing the rate of photosynthetic carbon fixation, which leads to increased biomass production, is beneficial for plants because of the high CO2 concentrations. At the same time, rising temperatures and periods of drought cause plant stress, and the rise in carbon dioxide concentration is also linked to this. Plant species from the Brassicaceae family (such as Brassica oleracea variety gongylodes, Brassica oleracea variety capitate, and Raphanus sativa) grown in high carbon dioxide environments were used to test the drought resistance. Short periods of drought have influenced the leaf's photosynthetic parameters, volatile organic compound emission, chlorophyll content, and flavonoid content. We have demonstrated that plants grown at more than 800 ppm carbon dioxide concentrations are more vulnerable to drought stress than plants grown at 400 ppm CO2.