**3. Results**

#### *3.1. Growth Parameters, RWC, and Tolerance Index (TI)*

After 7 days of V treatment, the growth traits of sweet potato were significantly influenced by the treatment of V stress (Figure 1). The phenotypic parameters, such as PH, LA, LN, shoot and root FW, DW, SDSI, and RDSI were increased at 10 mg L−<sup>1</sup> V treatment. Conversely, a significant reduction in the mentioned parameters was observed at 25, 50, and 75 mg L−<sup>1</sup> V treatment compared to the control (*p* < 0.05; Tables 1 and 2). The PH (8.6%), LN (11.7%), LA (7.6%), SFW (14%), RFW (16.4%), SDW (25.5%), RDW (28.9%), root-to-shoot ratio (3.1%), SDSI (25.5%), and RDSI (30.2%) were increased at 10 mg L−<sup>1</sup> V treatment than the control. In contrast, at higher concentrations, V treatment showed a negative correlation with plant growth. Furthermore, a drastic reduction in the PH (40.6%), LN (58.8%), LA (61.1%), SFW (57.8%), RFW (68.6%), SDW (62.2%), RDW (77.2%), root-to-shoot ratio (38.8%), SDSI (62.1%), and RDSI (76.3%) were observed at 75 mg L−<sup>1</sup> V treatment (Tables 1 and 2). Moreover, RWC in the leaves of sweet potato reduced significantly as the level of V treatment increased, and the utmost reduction was noted at 75 mg L−<sup>1</sup> V treatment (Table 1).

**Figure 1.** The influence of various V treatments on the growth of sweet potato.


**Table 1.** The influence of various V treatments on growth parameters of sweet potato.

Duncan's test indicates a significant difference (*p* < 0.05) between the means of the five treatments indicated by different alphabetical letters.

**Table 2.** The influence of various V treatments on root and shoot dry weight and root and shoot dry weight susceptibility index of sweet potato.


Duncan's test indicates a significant difference (*p* < 0.05) between the means of the five treatments indicated by different alphabetical letters.

#### *3.2. Root Morphology*

The root growth of sweet potato was induced significantly at 10 mg L−<sup>1</sup> V treatment; however, 25, 50, and 75 mg L−<sup>1</sup> V treatments presented a significant reduction in the root characteristics (Figure 2). The root length (13.1%), volume (48.6%), average diameter (13.3%), surface area (8.7%), projected area (32.5%), length per volume (15%), and crossing (17.1%) were more enhanced under 10 mg L−<sup>1</sup> V than the control. The tips and forks of the roots reduced by 2.6% and 24.2%, respectively, at 10 mg L−<sup>1</sup> V (Figure 2A–I). Conversely, a substantial reduction was detected from 25 to 75 mg L−<sup>1</sup> V treatments, and a highest decrease in root characteristics was observed at 75 mg L−<sup>1</sup> V treatment. The maximum reduction in the root length was 81%; likewise, root volume exhibited 41%, surface area 84.6%, average diameter 39.3%, projected area 80.9%, tips 82.6%, forks 89.2%, crossing 86.8%, and length per volume 81.5% reduction at 10 mg L−<sup>1</sup> V treatment (Figure 2A–I).
