## 3 Results and Discussion
### Assessment of Phytotoxicity
#### 3.2.2 Soil Application  
Table 5 shows the contents of chlorophyll a, b, total chlorophyll and carotenoids in wheat leaves exposed to each of SPs and Cu NPs via a soil application. By inspecting the data pertaining to SPs treatment, it can be deduced that chlorophyll (a) decreased relative to the control yielding 2.13 mg/g fresh weight at the concentration of 0.06 mg/mL 14 days after application. However, no significant difference in chlorophyll (a) content was observed after 7 days of application. On the contrary, treatment with Cu NPs significantly increased the chlorophyll (a) content recording 2.59 and 5.13 mg/g fresh weight at 0.06 mg/mL after 7 and 14 days from application, respectively. Chlorophyll (b) followed a rather different behavior to that of chlorophyll (a) upon soil exposure to either SPs or Cu NPs after 7 days of application, but a similar behavior after 14 days of application. With SPs treatments, chlorophyll (b) decreased significantly as compared to the control yielding 1.46 and 1.44 mg/g fresh weight after 7 and 14 days from the application of 0.06 mg/mL SPs, respectively. The treatment with Cu NPs, on the other hand, increased the content to 4.26 mg/g fresh weight after 14 days from the application of 0.06 mg/mL. However, no significant change in chlorophyll (b) content was observed after 7 days from the application of the same concentration of Cu NPs. Thus, eventually after 14 days of application, both chlorophyll (a) and (b) decreased upon treatment with SPs, whereas they both increased when subjected to Cu NPs treatment. Chlorophyll (a), therefore, followed the same behavior as chlorophyll (b) since the latter has been reported to prevent chlorophyll (a) from degradation during the photosynthesis process. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{Chlorophyll} & \multicolumn{4}{c}{Total Chlorophyll (\(\alpha\)+b)} & \multicolumn{4}{c}{Carotenoids} \\ \hline \multicolumn{2}{c}{**Concentration**} & \multicolumn{2}{c}{**7 DEA \({}^{\ast}\)**} & \multicolumn{2}{c}{**14 DFA**} & & & & & \\
**mg/mL** & \multicolumn{2}{c}{**a**} & \multicolumn{2}{c}{**b**} & \multicolumn{2}{c}{**a**} & \multicolumn{2}{c}{**b**} & \multicolumn{2}{c}{**c} & \multicolumn{2}{c}{**c} & \multicolumn{2}{c}{**c} \\ \hline \multirow{5}{*}{SPs} & Cont. & 2.22 \({}^{\rm d}\) \(\pm\) 0.18 & 1.93 \({}^{\rm a}\) \(\pm\) 0.25 & 3.71 \({}^{\rm c}\) \(\pm\) 0.10 & 2.56 \({}^{\rm c}\) \(\pm\) 0.15 & 4.15 \({}^{\rm d}\) \(\pm\) 0.07 & 6.27 \({}^{\rm c}\) \(\pm\) 0.25 & 0.46 \({}^{\rm c}\) \(\pm\) 0.06 & 0.60 \({}^{\rm c}\) \(\pm\) 0.04 \\  & 0.004 & 2.80 \({}^{\rm h}\) \(\pm\) 0.19 & 1.94 \({}^{\rm a}\) \(\pm\) 0.03 & 2.95 \({}^{\rm d}\) \(\pm\) 0.06 & 2.10 \({}^{\rm d}\) \(\pm\) 0.07 & 4.74 \({}^{\rm h}\) \(\pm\) 0.22 & 5.05 \({}^{\rm d}\) \(\pm\) 0.13 & 0.45 \({}^{\rm h}\) \(\pm\) 0.01 & 0.50 \({}^{\rm d}\) \(\pm\) 0.02 \\  & 0.03 & 2.34 \({}^{\rm d}\) \(\pm\) 0.22 & 1.63 \({}^{\rm h}\) \(\pm\) 0.12 & 2.70 \({}^{\rm c}\) \(\pm\) 0.04 & 1.92 \({}^{\rm c}\) \(\pm\) 0.07 & 3.97 \({}^{\rm d}\) \(\pm\) 0.34 & 4.62 \({}^{\rm c}\) \(\pm\) 0.11 & 0.39 \({}^{\rm h}\) \(\pm\) 0.03 & 0.45 \({}^{\rm c}\) \(\pm\) 0.02 \\  & 0.06 & 2.20 \({}^{\rm d}\) \(\pm\) 0.01 & 1.46 \({}^{\rm h}\) \(\pm\) 0.05 & 2.13 \({}^{\rm c}\) \(\pm\) 0.00 & 1.44 \({}^{\rm d}\) \(\pm\) 0.01 & 3.66 \({}^{\rm d}\) \(\pm\) 0.05 & 3.57 \({}^{\rm c}\) \(\pm\) 0.01 & 0.34 \({}^{\rm d}\) \(\pm\) 0.01 & 0.34 \({}^{\rm d}\) \(\pm\) 0.00 \\ \hline \multirow{2}{*}{Cu NPs} & 0.004 & 2.14 \({}^{\rm a}\) \(\pm\) 0.04 & 1.50 \({}^{\rm h}\) \(\pm\) 0.05 & 2.96 \({}^{\rm d}\) \(\pm\) 0.07 & 2.21 \({}^{\rm d}\) \(\pm\) 0.14 & 3.64 \({}^{\rm d}\) \(\pm\) 0.01 & 5.17 \({}^{\rm d}\) \(\pm\) 0.21 & 0.35 \({}^{\rm h}\) \(\pm\) 0.01 & 0.52 \({}^{\rm d}\) \(\Carotenoids decreased significantly with an increasing concentration of SPs, recording 0.34 mg/g fresh weight after 7 days of treatment with 0.06 mg/mL SPs, while no change was observed in total chlorophyll content at that concentration of SPs.