*4.4. Enzymatic Antioxidant Activities (SOD, POD, CAT, and APx)*

Low-temperature treatment caused a significant decrease in SOD activity in all varieties except Y49 and M33 in cold-induced leaves shown in Figure 3a. The activity of SOD during low-temperature stress was dramatically reduced in most of the varieties compared with control. In contrast, the Y49 and M33 had an increasing trend, which only increased by 5.16% and 14.13%, respectively.

Our experiment revealed that POD activity significantly decreased in Y38, T8 followed by W57 cultivar compared to control (Figure 3b). Conversely, POD activity was increased higher in both Y49 and M33 cultivars. There was a substantial difference in CAT activity between all varieties between control and stress conditions in our study. CAT activity decreased significantly in most of the varieties compared to the control (Figure 3c). There was a much lower level of CAT activity in Y1, Y38, and T8 after low temperature stresses Y49 and M33 than the control, whereas Y49 and M33 increased the CAT activity by 50.87% and 25.80%, respectively.

Cold treatment also had a significant effect on APx activity in the treatment leaves; however, cold treated leaves of the Y49, Y33, M33, T8, and M18 varieties exhibited an increasing trend in APx activity, whereas T8 and W57 exhibited a decreasing trend (Figure 3d). It was observed that Y49 and M33 enhanced by 47.5% and 84.79%, respectively compared with those of the non-stress condition. Increased APX activity in low temperature-treated leaves of Y49 and M33 may indicate that Apx interferes with cold signal transduction.

**Figure 3.** Influence of cold stress on leaf antioxidant and enzymatic antioxidants in jute varieties. Plants under control (28 ◦C) and stress (5 ◦C) showed a response in: (**a**) Superoxidase dismutase (SOD) activity, (**b**) Peroxidase (POD) activity (**c**) Catalase (CAT) activity and (**d**) APx activity. Different significant level marked with \*\*\*\* *p* < 0.0001, \*\*\* *p* ≤ 0.001, \*\* *p* ≤ 0.01, \* *p* ≤ 0.05, and ns mean non-significant.
