The multi-walled carbon nanotubes induced anatomical and morphological changes in root and shoot of two cultivars of Okra (Hibiscus escolentus L.) seedlings

Carbon nanotubes (CNTs) are known to have many unique physical and chemical properties. Because of these features, they accelerate the germination process, root growth, and photosynthesis rate that can result in increased crop productivity. In the present study, the effects of 4 multi-walled carbon nanotubes (MWCNTs) levels including 0 (control), 50 (low concentration), 100 (moderate concentration), and 200 (high concentration) mg/l were evaluated on morphological and anatomical characteristics of stem, root and leaf in two Okra cultivars namely Bamia and Emerald. In both cultivars, the value of height and biomass of shoot and root increased after addition of 50 and 100 mg/l MWCNTs. Based on microscopic results, the root and shoot diameters in both cultivars more affected by increased cortex thickness and central cylinder in 50 and 100 mg/l of MWCNTs treatments whereas these parameters were more affected by increased cortex thickness in the high concentration of MWCNTs. Our study indicated that the thickness of mesophylls and spongy layers increased in low level of MWCNT, whereas these parameters were decreased in moderate and high levels of MWCNT in both cultivars. The statistical analysis showed that Stomata size increased value in low and moderate levels of MWCNT in Bamia cultivar. In this study Stomata index measurement showed that this parameter was increased in moderate and high levels of MWCNT only in Emerald cultivar. We observed that diameter of xylem and phloem in the shoot were increased in low (50 mg/l) and moderate (100 mg/lit) levels of MWCNTs whereas these parameters were decreased in high MWCNT level. Although this study revealed that low treatments of MWCNTs caused an increase of root xylem diameter in both cultivars.