The Impact of Increased CO 2 and Drought Stress on the Secondary Metabolites of Cauliflower ( Brassica oleracea var. botrytis ) and Cabbage ( Brassica oleracea var. capitata ).

Elevated carbon dioxide and drought are significant stressors in light of climate change. This study explores the interplay between elevated atmospheric CO 2 , drought stress, and plant physiological responses. Two Brassica oleracea varieties (cauliflowers and cabbage) were utilized as model plants. Our findings indicate that elevated CO 2 accelerates assimilation rate decline during drought. The integrity of photosynthetic components influenced electron transport, potentially due to drought-induced nitrate reductase activation changes. While CO 2 positively influenced photosynthesis and water-use efficiency during drought, recovery saw decreased stomatal conductance in high-CO 2 -grown plants. Drought-induced monoterpene emissions varied, influenced by CO 2 concentration and species-specific responses. Drought generally increased polyphenols, with an opposing effect under elevated CO 2 . Flavonoid concentrations fluctuated with drought and CO 2 levels, while chlorophyll responses were complex, with high CO 2 amplifying drought's effects on chlorophyll content. These findings contribute to a nuanced understanding of CO 2 -drought interactions and their intricate effects on plant physiology.