## 3 Results and Discussion
### Dry Weight and Total Phenolic Contents  
Table 6 shows the effect of SPs and Cu NPs on the dry biomass of wheat in both foliar and soil applications, respectively. Clearly, the dry biomass increased significantly with an increasing concentration of SPs to 0.06 mg/mL, thus recording 0.78 and 0.56 g/plant in foliar and soil applications, respectively. The same stimulant effect was reported for seaweed extracts on sunflowers [56]. Although a decrease in the total chlorophyll and carotenoids was previously observed after 14 days of application of SPs, yet it can be inferred that the plant overcame this effect after 28 days by producing antioxidants as a defense mechanism. Plants can survive under the oxidative stress of biotic or abiotic SPs by exhibiting adaptive biochemical responses that entail the production of antioxidant compounds or enzymes. Antioxidative defense systems can be nonenzymatic involving, for example, an increase in the total phenolic content, or enzymatic employing peroxidase (POD) and catalase (CAT) enzymes. These defense mechanisms protect plants against oxidative stress damage and enhance its growth [50; 57]. This hypothesis can be confirmed by inspecting Figure 4a,b which depict the total phenolic content (TPC) of wheat leaves upon exposure to SPs and Cu NPs in foliar and soil applications, respectively. As can be observed in (Figure 4a,b), the TPC significantly increased relative to the control upon increasing the concentration of SPs to 0.06 mg/L, thus recording 16.59 and 8.13 mg GA/g in foliar and soil applications, respectively. A positive correlation between antioxidant activity and TPC has been previously reported [21]. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Concentration**} & \multicolumn{2}{c}{**DW Foliar Application (g)**} & \multicolumn{2}{c}{**DW Soil Application (g)**} \\ \cline{2-5}  & **SPs** & **Cu NPs** & **SPs** & **Cu NPs** \\ \hline
0 & 0.49 b \(\pm\) 0.06 & 0.49 b \(\pm\) 0.06 & 0.33 b \(\pm\) 0.14 & 0.33 b\(\pm\) 0.14 \\
0.004 & 0.51 b \(\pm\) 0.04 & 0.81 a \(\pm\) 0.1 & 0.19 ab \(\pm\) 0.14 & 0.44 b\(\pm\) 0.11 \\
0.03 & 0.73 a \(\pm\) 0.1 & 0.66 ab \(\pm\) 0.19 & 0.17 c \(\pm\) 0.08 & 0.31 abc \(\pm\) 0.09 \\
0.06 & 0.78 a \(\pm\) 0.14 & 0.46 b \(\pm\) 0.07 & 0.56 a \(\pm\) 0.12 & 0.34 ab \(\pm\) 0.09 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Effect of SPs and Cu NPs on the dry weight of wheat in foliar and soil applications. On the other hand, treatment with Cu NPs showed no effect on the dry weight of wheat plants in both foliar and soil applications. However, it augmented the TPC where the highest contents of 18.69 and 9.69 were obtained upon foliar and soil application of 0.06 mg/mL of Cu NPs. The promoting effect of nanoparticles on the total phenolic content was previously observed in _Dracocephalus molavica_ leaves upon exposure to Ag NPs [50]. Thus, it can be deduced that the plant resisted the inhibition effect of Cu NPs by producing antioxidants. Consequently, the plant dry weight was maintained via this defense mechanism. To compare plant growth and development at different time points upon a foliar or soil application with the highest concentration (0.06 mg/mL) of SPs or Cu NPs, Figure 5 was constructed to show chlorophyll and carotenoids contents after 7 and 14 days of application. In the foliar application after 7 and 14 days, the chlorophyll and carotenoid contents obtained after the Cu NPs treatment were higher than their counterparts obtained upon SPs treatment. A significant difference, however, was observed with the 14-day application only. Relative to the control, the reduction in chlorophyll and carotenoid contents with Cu NPs treatment was less than that encountered with SPs treatment. Hence, Cu NPs have less inhibitory effect than that of SPs due to the reasons alluded to earlier. In soil application, SPs also showed significant inhibitory effects, however Cu NPs significantly stimulated growth after 14 days of application.