Single-wall carbon nano tubes (SWCNTs) encourage the biosynthesis of bioactive compounds in plants. The current study examined how SWCNTs affect morphological, physiological and biochemical properties of Thyme (Thymus daenensis) callus culture. Sterilized seeds were cultured in Murashige and Skoog (MS) medium. Ten-dayold seedlings were used as explants and were cultured on MS media containing 2, 4-dichlorophenoxy acetic acid (2, 4-D) (2 mg l???? 1) and benzyl amino purine (BAP) (4 mg l???? 1). These media were treated with various concentrations of SWCNTs (25, 50, 100, 125, and 250 μg ml???? 1). A medium without SWCNTs was considered as the control. This study finding revealed that SWCNTs induce changes in callus morphology (i.e. color changes, area, fresh, and dry weight) and physiology (i.e. water content and dehydrogenase activity) as SWCNTs activate antioxidant molecules and some related enzymes (e.g. peroxidase (POD), polyphenol oxidase (PPO), phenylalanine ammonia-lyase (PAL), and Dehydrogenase (DHA)). SWCNTs contribute to the accumulation of compounds that are pharmacologically active (e.g. phenolic acids and flavonoids) in a concentration-dependent manner. Adding SWCNTs to the extracts of callus created a variety of 1, 1-diphenyl-2-picrylhydrazyl radical (DPPH) free radical scavenging activities in the extracts. At the cellular level, optical microscopic images indicated that SWCNTs can reasonably promote cell elongation and reduce chloroplast numbers. Following the addition of SWCNTs to the media, after 30 and 60 days, SWCNTs (50 μg ml???? 1) were found to encourage better growth in terms of both fresh (0.683 ± 0.50 g, 1.667 ± 1.18 g) and dry biomass (0.058 ± 0.12 g, 0.266 ± 0.17 g), respectively. Also, SWCNTs (50 μg ml???? 1) increased total phenolic content (TPC) (1.290 ± 0.19 mg GAE g ???? 1 DW), total flavonoids content (TFC) (2.113 ± 0.05 mg QUE g ???? 1 DW), antioxidant activity (74.93 ± 3.1 %), Rosmarinic acid (22.10 ± 0.011 mg. g???? 1DW), Trans-ferulic acid (0.29 ± 0.02 mg. g???? 1DW), Catechin (0.44 ± 0.002 mg. g???? 1DW), Hesperedin (0.45 ± 0.02 mg. g???? 1DW), Vanilin (0.13 ± 0.01 mg. g???? 1DW), Carvacrol (0.068 ± 0.01 mg. g???? 1DW) and enzymes that facilitate the biosynthesis of phenolic compounds like PAL (32.94 ± 13.2 mM cm g ???? 1 FW). In addition, Transmission electron microscopy (TEM) images of T. daenensis callus cells revealed how SWCNTs nano materials can penetrate callus cells and then aggregate together in the cytoplasm and in the cell wall.

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