Effect of Elevated CO₂ on Biomolecules' Accumulation in Caraway (Carum carvi L.) Plants at Different Developmental Stages

Caraway plants have been known as a rich source of phytochemicals, such as flavonoids, monoterpenoid glucosides and alkaloids. In this regard, the application of elevated CO₂ (eCO₂) as a bio-enhancer for increasing plant growth and phytochemical content has been the focus of many studies; however, the interaction between eCO₂ and plants at different developmental stages has not been extensively explored. Thus, the present study aimed at investigating the changes in growth, photosynthesis and phytochemicals of caraway plants at two developmental stages (sprouts and mature tissues) under control and increased CO₂ conditions (ambient CO₂ (a CO₂, 400 ± 27 μmol CO₂ mol^-1 air) and eCO₂, 620 ± 42 μmol CO₂ mol^-1 air ppm). Moreover, we evaluated the impact of eCO₂-induced changes in plant metabolites on the antioxidant and antibacterial activities of caraway sprouts and mature plants. CO₂ enrichment increased photosynthesis and biomass accumulation of both caraway stages. Regarding their phytochemical contents, caraway plants interacted differently with eCO₂, depending on their developmental stages. High levels of CO₂ enhanced the production of total nutrients, i.e., carbohydrates, proteins, fats and crude fibers, as well as organic and amino acids, in an equal pattern in both caraway sprouts and mature plants. Interestingly, the eCO₂-induced effect on minerals, vitamins and phenolics was more pronounced in caraway sprouts than the mature tissues. Furthermore, the antioxidant and antibacterial activities of caraway plants were enhanced under eCO₂ treatment, particularly at the mature stage. Overall, eCO₂ provoked changes in the phytochemical contents of caraway plants, particularly at the sprouting stage and, hence, improved their nutritive and health-promoting properties.