Besides the lack of studies regarding applying elevated CO2 (eCO2) as a strategy to improve the chemical composition of anise (Pimpinella anisum L.) seeds, studies on its interaction with seed developmental stages and origin are very limited. The seed yield, chemical composition, and biological activity of 6 aniseed accessions (Egypt, Tunisia, Syria, Turkey, Yemen, and Morocco) were investigated during three developmental stages (immature, premature, and mature) under control and elevated CO2 conditions. Mature seeds from all aniseed accessions had significantly higher (p < 0.05) dry weight (DW) percentages than premature and immature seeds. The highest DW percentages were recorded in Egypt and Morocco accessions. Seed maturation increased nutrients and antioxidant metabolites in most eCO2-treated accessions. In contrast, essential oils were decreased by seed maturation, while eCO2 reversed this effect. Essential oil-related precursors (e.g., phenylalanine) and enzyme activities (3-Deoxy-d-arabino-heptulosonate-7-phosphate synthase (DAHPS) and O-methyltransferase) decreased with seed maturity. However, high CO2 reduced this impact and further induced the other essential oil-related precursors (shikimic and cinnamic acids). Consequently, eCO2 provoked changes in the antioxidant and hypocholesterolemic activities of aniseeds, particularly at mature stages. Overall, eCO2 application, as an efficient way to improve aniseed growth, essential oil metabolism, and chemical composition, was affected by seed maturation and origin. Future studies of eCO2-treated aniseeds as a nutraceutical and pharmaceutical product are suggested.
Keywords: aniseed; elevated CO2; essential oil metabolism; plant origin; seed maturity.