Multi-walled carbon nanotubes improved growth, anatomy, physiology, secondary metabolism, and callus performance in Catharanthus roseus: an in vitro study

This study was conducted to monitor the physiological and molecular responses of Catharanthus roseus (rose periwinkle) to multi-walled carbon nanotube (MWCNT) incorporation into the culture medium. The seeds were grown on hormone-free MS medium supplemented with 0, 50, 100, and 150 mgL(-1)of MWCNT. The supplementations of culture medium with MWCNTs led to significant increases in plant growth indexes such as leaf width, leaf area, leaf fresh weight, root length, and total plant biomass). Slight increases were also observed in chlorophyll a (Chla), Chlb, and carotenoid contents (mean = 18.6%) in MWCNT-treated seedlings. Protein concentrations increased by an average of 34% relative to the control. The application of MWCNT resulted in twofold increases in the catalase and peroxidase activities. A similar trend was also observed in the phenylalanine ammonia lyase activities (by an average of 36.5%), soluble phenols (by 23%), and alkaloids (by 1.7-fold). Moreover, upregulations (mean = 37-fold) in the transcriptions of the DAT gene resulted from the MWCNT supplementations. Exposure to MWCNT improved cell sizes and xylem conducting tissue in treated seedlings. The applications of MWCNTs also stimulated the callus initiation and performance, implying their effects on proliferation and possible differentiation. This study has provided evidence of role MWCNT play in improving plant performance and production of pharmaceutical secondary metabolites.