*3.6. Lipid Peroxidation (MDA) and Reactive Oxygen Species (H2O2) Content*

The V treatment considerably provoked MDA and H2O2 levels in the leaves (*p* < 0.05; Figure 5A,B). The rise of V treatment caused an increase in MDA and H2O2 content; the highest MDA and H2O2 content was present in 75 mg L−<sup>1</sup> V treatment compared to the control. The MDA content in 75 mg L−<sup>1</sup> V was 928.9% higher than the control (Figure 5A), where the H2O2 content was 665% higher (Figure 5B).

**Figure 5.** The influence of various V treatments on the production of reactive oxygen species (ROS) and lipid peroxidation in the leaves of sweet potato. (**A**) Malondialdehyde (MDA) and (**B**) hydrogen peroxide (H2O2) content. Duncan's test specifies a significant difference (*p* < 0.05) between the means of the five treatments indicated by different alphabets.

#### *3.7. Osmolytes Production*

The proline content was significantly increased as the level of V increased (*p* < 0.05). The maximum rise of 448.3% in proline content was detected at 75 mg L−<sup>1</sup> V treatment (Figure 6A). Soluble sugars were also significantly higher in V-treated plants (*p* < 0.05). The content of soluble sugars in the leaves of sweet potato was increased to 50 mg L−1; however, at 75 mg L−<sup>1</sup> V, the content of soluble sugars decreased but was still significantly higher (97.6%) than the control plants (Figure 6B). Furthermore, the results exhibited that the total proteins were significantly increased at 10 mg L−<sup>1</sup> V treatment; later, a significant decrease was observed at a higher level of V treatment (*p* < 0.05). The lowest protein content (0.029 mg g<sup>−</sup>1) was observed at 75 mg L−<sup>1</sup> V treatment compared to the control (Figure 6C).

**Figure 6.** The influence of various V treatments on the osmolytes production in the leaves of sweet potato. (**A**) Proline content, (**B**) soluble sugars, and (**C**) total protein content. Duncan's test indicates a significant difference (*p* < 0.05) between the means of the five treatments indicated by different alphabetical letters.
