## 3 Results and Discussion
### Assessment of Phytotoxicity
#### 3.2.1 Foliar Application
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{Chlorophyll} & \multicolumn{4}{c}{Total Chlorophyllly1 (a + b)} & \multicolumn{4}{c}{Carotenoids} \\ \hline \multicolumn{2}{c}{**Concentration**} & \multicolumn{4}{c}{**7 DEA \({}^{\ast}\)**} & \multicolumn{4}{c}{**14 DFA**} & \\ \multicolumn{2}{c}{**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. & 4.34\({}^{\pm}\) 0.07 & 3.42\({}^{\pm}\) 0.04 & 6.40\({}^{\pm}\) 0.14 & 6.04\({}^{\pm}\) 0.35 & 7.76\({}^{\pm}\) 0.11 & 12.44\({}^{\pm}\) 0.49 & 0.81\({}^{\pm}\) 0.01 & 1.44\({}^{\pm}\) 0.09 \\  & 0.004 & 3.94\({}^{\pm}\) 0.17 & 3.07\({}^{\pm}\) 0.19 & 6.03\({}^{\pm}\) 0.27 & 5.27\({}^{\pm}\) 0.52 & 7.01\({}^{\pm}\) 0.36 & 11.30\({}^{\pm}\) 0.24 & 0.73\({}^{\pm}\) 0.05 & 1.26\({}^{\pm}\) 0.13 \\  & 0.03 & 3.82\({}^{\pm}\) 0.41 & 2.87\({}^{\pm}\) 0.56 & 5.93\({}^{\pm}\) 0.03 & 5.05\({}^{\pm}\) 0.02 & 6.69\({}^{\pm}\) 0.15 & 10.98\({}^{\pm}\) 0.05 & 0.68\({}^{\pm}\) 0.14 & 1.20\({}^{\pm}\) 0.01 \\  & 0.06 & 3.61\({}^{\pm}\) 0.27 & 2.82\({}^{\pm}\) 0.23 & 4.90\({}^{\pm}\) 0.05 & 4.06\({}^{\pm}\) 0.07 & 6.43\({}^{\pm}\) 0.50 & 8.96\({}^{\pm}\) 0.12 & 0.67\({}^{\pm}\) 0.06 & 0.97\({}^{\pm}\) 0.02 \\ \hline \multirow{5}{*}{Cu NPs} & 0.004 & 4.31\({}^{\pm}\) 0.06 & 3.49\({}^{\pm}\) 0.13 & 6.38\({}^{\pm}\) 0.03 & 5.94\({}^{\pm}\) 0.00 & 7.80\({}^{\pm}\) 0.19 & 12.32\({}^{\pm}\) 0.03 & 0.83\({}^{\pm}\) 0.03 & 1.42\({}^{\pm}\) 0.00 \\  & 0.03 & 4.22\({}^{\pm}\) 0.16 & 3.32\({}^{\pm}\) 0.25 & 0.54\({}^{\pm}\) 0.01 & 6.40\({}^{\pm}\) 0.07 & 7.54\({}^{\pm}\) 0.31 & 12.94\({}^{\pm}\) 0.06 & 0.79\({}^{\pm}\) 0.04 & 1.53\({}^{\pm}\) 0.02 \\  & 0.06 & 4.10\({}^{\pm}\) 0.35 & 2.94\({}^{\pm}\) 0.46 & 5.68\({}^{\pm}\) 0.19 & 4.60\({}^{\pm}\) 0.30 & 7.04\({}^{\pm}\) 0.11 & 10.28\({}^{\pm}\) 0.11 & 0.69\({}^{\pm}\) 0.11 & 1.09\({}^{\pm}\) 0.07 \\ \hline LSD & & 0.486 & 0.546 & 0.346 & 0.533 & 0.500 & 0.496 & 0.133 & 0.126 \\ \hline \multicolumn{2}{c}{\({}^{\ast}\)**DFA** days from application.} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\ \hline \end{tabular}
\end{table} 
Table 4: Chlorophyll and carotenoids contents (mg/g fresh weight) in wheat leaves exposed to a foliar application of SPs and Cu NPs. From the above, it can be deduced that the treatment of wheat plants with 0.06 mg/mL of either SPs or Cu NPs significantly reduced the total chlorophyll and carotenoids contents relative to the control after 14 days of application. This reflects the inhibitory effects of both SPs and Cu NPs on plant growth. However, the inhibitory effect of SPs was slightly more pronounced than that of Cu NPs since treatment with SPs reduced the respective total chlorophyll and carotenoids contents by 27.9% and 32.6% relative to the control, whereas the treatment with Cu NPs reduced them by 17.4% and 24.3%, respectively. This behavior is slightly different than that observed in seed germination where the inhibitory effects of SPs and Cu NPs were comparable. The pathways of Cu NPs uptake or absorption in seed germination where the nanoparticles can easily cross the cell membrane is different from its pathway in foliar applications where metal penetration can take place via the stomatal pores of the leaves. The transport of Cu NPs into the leaves might have thus been governed by diffusional resistances that were slightly less encountered during the transport of SPs which are free in solution [52; 53]. Despite the slightly higher inhibitory effect shown by SPs relative to Cu NPs, their effects could still be considered comparable since the reduction in total chlorophyll and carotenoids contents upon treatment with SPs exceed that obtained with Cu NPs by no more than 10% as is clear from the values given above.