Application of iron oxide nanoparticles improves growth and phytochemical constituents of in vitro cultured Carum copticum L.

Iron oxide nanoparticles (FeONPs) are widely used in various applications, such as biomedicine, environmental remediation, and agriculture. Moreover, FeONPs can affect the production of secondary metabolites in plants, which are compounds that have various biological and pharmacological activities. Therefore, in this study, the ajwain ( Carum copticum L.) seeds were grown in MS medium containing different levels of FeONPs (0, 100, 200, and 400 mg l −1 ). After four weeks, the effects of FeONPs on growth, photosynthesis pigments, total phenolic, and anthocyanin content, activities of some antioxidant enzyme and secondary metabolites of ajwain) were investigated. The results showed that low levels of FeONPs (especially 200 mg l −1 ) increased fresh weight (231 %), total chlorophyll (49 %), total phenolics (259 %), anthocyanin content (110 %), as well as thymol (8 %) and γ-terpinene (16 %) content. Conversely, 400 mg l −1 FeONPs reduced root length (60 %) and fresh weight (64 %) was associated with a reduction in CAT activity, phenol (55 %), thymol (22 %), and γ-terpinene (18 %) content compared to ajwain treated with 200 mg l −1 FeONPs. This reduction was probably due to the increase in ROS caused by the low catalase enzyme activity and important essential oils compounds such as thymol and γ-terpinene. Thus, our results indicate that FeONPs at certain levels can be used as a new way for in vitro production of valuable essential oils and antioxidant compounds in ajwain. • FeONPs influence the growth, photosynthetic pigments, and secondary metabolites of ajwain. • Low levels of FeONPs (200 mg l −1 ) enhance the production of secondary metabolites and antioxidant enzymes activity of ajwain. • FeONPs (200 mg l −1 ) increased total phenolics (259 %), anthocyanin content (110 %), as well as thymol (8 %) and γ-terpinene (16 %) content. • High levels of FeONPs (400 mg l −1 ) have negative effects on the plant's physiology and biochemistry. • FeONPs (400 mg l −1 ) reduced the root length and fresh weight of the ajwain plants.