## 2 Results and Discussion
### Effect of Nanoparticle on Gene Expression
#### 2.5.2 GPPS1 Gene Expression Analysis Result  
The relative expression levels of the FPPS1 gene were analyzed in leaves of _P. gravelens_ and _S. alba_ plants treated with GW NPs (0.5 g/L) and Mg NP/GW (Figure 11 and Table 6). Under GW NP (0.5 g/L) treatment, both _S. alba_ and _P. gravelens_ exhibited significantly elevated fold changes in FPPS1 gene expression compared to the control (_S. alba_: a \(>\) b, and _P. gravelens_: b \(>\) c). Notably, _S. alba_ showed a higher fold change (25.244 \(\pm\) 0.004) than _P. gravelens_ (21.58 \(\pm\) 0.03) under this condition. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Treatment** & **Plant** & **Relative Expression (Fold Changes)** \\ \hline \multirow{2}{*}{Control} & _S. alba_ & 1.0 \(\pm\) 0.03  \\  & _P. gravelens_ & 1.0 \(\pm\) 0.03  \\  & _S. alba_ & 18.1340 \(\pm\) 0.002  \\  & _P. gravelens_ & 14.574 \(\pm\) 0.003  \\  & _S. alba_ & 11.273 \(\pm\) 0.04  \\  & _P. gravelens_ & 6.477 \(\pm\) 0.004  \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Relative gene expression level (fold changes) of GPPS1 gene in plants growing under nanoparticles application; data values expressed as (Mean \(\pm\) SD). Figure 10: Comparison between (fold changes) of FPPS1 gene in _P. gravelens_ and _S. alba_ plants growing under (0.5 g/L) GW NP and Mg NP/GW application. Similarly, under Mg NP (0.5 g/L) treatment, both species showed significantly increased FPPSI gene expression compared to the control (_S. alba_: c > control, and _P. gravelens_: c > control). However, the fold changes induced by Mg NPs were generally lower than those induced by GW NPs. Once again, _S. alba_ exhibited a higher fold change (13.4539 \(\pm\) 0.002) compared to _P. gravelens_ (12.15676 \(\pm\) 0.0025) under this treatment. In general, both _S. alba_ and _P. gravelens_ demonstrated enhanced FPPSI gene expression in response to GW NP and Mg NP treatments compared to the control. GW NPs induced higher fold changes in gene expression compared to Mg NPs, and _S. alba_ consistently exhibited higher fold changes than _P. gravelens_ across both nanoparticle treatments. The heat map in Figure 12 illustrates the results, where each treatment is sorted into two primary clusters: GW- and Mg NP/GW-treated plants in one cluster, and untreated control plants in the other. The highest mRNA expression levels were observed for the FPPSI gene, with 25.24- and 21.68-fold increases in expression in _S. alba_ and _P. gravelens_*, respectively. This was followed by 18.13- and 14.57-fold increases for the GPPSI gene in _S. alba_ and _P. gravelens_, respectively, while 13.45- and 12.16-fold increases were observed for the GPPSI gene in the same plants. The minimum expression levels were 11.28- and 6.48-fold increases for the GPPSI gene in the two plants, respectively. The analysis of RT-qPCR results for FPPSI and GPPSI genes in _S. alba_ and _P. gravelens_ plants revealed interesting findings regarding the mRNA expression levels of these genes in the two plant species. Similar results were reported by [54], showing the effect of silver nanoparticles on the expression of the FAE1 and FAD2 genes in _Camelina sativa_[55]. The mRNA levels of the FPPSI gene were notably elevated in both _S. alba_ and _P. gravelens_ plants, with fold changes of 25.24 and 21.68, respectively. These findings highlight a significant upregulation of the FPPSI gene, underscoring its pivotal role in the biological processes and metabolic pathways of these plant species. This observation is consistent with previous research emphasizing the central role of FPPSI in plant metabolism. The study by [56] underscored the importance of specific genes in secondary metabolite biosynthesis pathways, such as thymoquinone in Nigella sativa, demonstrating the relevance of gene expression profiling through RT-qPCR despite challenges posed by residual nanoparticles [57]. Figure 11: Comparison between (fold changes) of GPPSI gene in _P. gravelens_ and _S. alba_ plants growing under (0.5 g/L) GW NP and Mg NP/GW application.