Assessment of the effect of multi-walled carbon nanotubes (-OH functionalized) on growth characteristics and biochemical profile of Brassica juncea (L.) Czern. & Coss.

This study investigated the effect of various levels of OH-MWCNTs mediated seed priming on germination, growth, and biochemical responses of Indian mustard (Brassica juncea (L.) Czern. & Coss.). Germination efficiency declined significantly up to 33.8% with increasing concentration of OH-MWCNT; however, other growth characteristics including seedling length and weight exhibited a substantial increase of up to 61.6% and 142%, respectively, at moderate levels (≤ 100 µg mL). Higher doses (250 µg mL, 500 µg mL) of OH-MWCNT exhibited a toxic effect on all growth parameters resulting in ~ 20% and 55% decline in seedling length and biomass, respectively. Similar trend was recorded in chlorophyll content, and maximum total chlorophyll content (13 ± 3 mg/g FW) was noted at 100 µg/mL OH-MWCNT. Antioxidant enzyme activities including catalase (CAT), guaiacol peroxidase (GPX), polyphenol oxidase (PPO), and superoxide dismutase (SOD) also exhibited similar pattern such that all activities were maximum at 100 µgmL in both shoots and roots and were significantly higher in shoots than in roots. Total phenol content and DPPH activity were also maximum at 100 µgmL, and both parameters were comparatively higher in roots than in shoots. GC-MS analysis revealed that lipids constituted the majority of the proportion of secondary metabolites detected in non-polar extracts of both shoots and roots. Further, correlation analysis established a significant correlation between various growth, physiological, and biochemical parameters. These findings therefore indicated that moderate levels of OH-MWCNT concentrations can enhance B. juncea growth and biochemical responses, which in turn promotes biosynthesis of valuable antioxidant compounds. This study highlighs the potential of MWCNTs as innovative growth enhancers, wherein the higher concentrations may have detrimental effects, therefore, emphasizing the need for careful management of OH-MWCNT usage for agricultural purposes.