## 5 Silicon Accumulation Improves Plant Disease Resistance
### Formation of Biochemical Barriers as Influenced by Si  
Recent studies have shown that the biochemical mechanisms of Si play more important roles in improving plant disease resistance than the physical mechanisms [78]. The main \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Types of Disease** & **Plant** & **Disease Response of Si Deposition** & **Pathway** & **References** \\ \hline \multirow{4}{*}{Fungal pathogen} & Tomato & Improve resistance to anthracnose & Physical and Biochemical Barriers & [63] \\ \cline{2-5}  & & Improve resistance to root rot & Physical Barriers & [64] \\ \cline{2-5}  & & Improve resistance to early blight & Biochemical Barriers & [65] \\ \cline{2-5}  & Pumpkin & Improve resistance to powdery mildew & Physical Barriers & [16] \\ \hline \multirow{4}{*}{Fungal pathogen} & Oil palms & Improve resistance to powdery mildew & Physical Barriers & [66] \\ \cline{2-5}  & Coffee & Improve resistance to leaf rust & Physical Barriers & [67] \\ \hline \multirow{4}{*}{Fungal pathogen} & Pepper & Improve resistance to Phytophthora & Physical Barriers & [68] \\ \cline{2-5}  & Sprophium & Improve resistance to leaf spot & Physical Barriers & [69] \\ \cline{2-5}  & Rice & Improve resistance to brown spot & Physical Barriers & [62] \\ \cline{2-5}  & & Improve resistance to leaf Scald & Physical Barriers & [15] \\ \hline \multirow{4}{*}{Fungal pathogen} & Improve resistance to rice blast & Physical Barriers & [14; 70] \\ \cline{2-5}  & Improve resistance to sheath blight & Physical and Biochemical Barriers & [71] \\ \hline \multirow{4}{*}{Wheat} & Wheat & Improve resistance to leaf blast & Physical Barriers & [72] \\ \cline{2-5}  & Improve resistance to tan spot and fusarium & Physical Barriers & [73] \\ \cline{2-5}  & head blight & & & \\ \hline \multirow{4}{*}{Beans} & Improve resistance to Phytophthora & Biochemical Barriers & [74] \\ \cline{2-5}  & blight & & & \\ \hline \multirow{4}{*}{Fungal pathogen} & Improve resistance to frogeye leaf spot & Biochemical Barriers & [75] \\ \cline{2-5}  & Improve resistance to anthracnose & Biochemical Barriers & [76] \\ \hline \multirow{4}{*}{FerennialRyegrass} & Improve resistance to leaf spot & Biochemical Barriers & [77] \\ \cline{2-5}  & Bittergourd & Improve resistance to powdery mildew & Biochemical Barriers & [78] \\ \cline{2-5}  & Maize & Improve resistance to leaf spot & Physical and Biochemical Barriers & [79] \\ \hline \multirow{4}{*}{Fungal pathogen} & Cotton & Improve resistance to _Fusarium oxysporum_ & Physical and Biochemical Barriers & [80] \\ \cline{2-5}  & Rose & Improve resistance to powdery mildew & Physical and Biochemical Barriers & [81] \\ \cline{2-5}  & Potato & Improve resistance to late blight & Biochemical Barriers & [82] \\ \hline \multirow{4}{*}{Bacterial pathogen} & Tomato & Improve resistance to bacterial wilt & Biochemical Barriers & [18; 83; 84] \\ \cline{2-5}  & Melon & Improve resistance to bacterial fruit blotch & Physical Barriers & [85] \\ \cline{1-1} \cline{2-5}  & Banana & Improve resistance to black sigatoka & Physical Barriers & [86] \\ \cline{1-1} \cline{2-5}  & Beans & Improve resistance to leaf spot & Physical Barriers & [40] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Studies showing the beneficial role of Si in alleviating disease-associated stress. way to resist the invasion of pathogenic bacteria through physiological and biochemical defense mechanisms is to increase the activity of plant leaf protective enzymes, such as peroxidase, polyphenol oxidase and phenylalanine ammonialylase, and induce the host to synthesize secondary metabolic antimicrobial compounds, such as phenolic metabolic products, phytoalexins and pathogenesis-related proteins. Thus, Si activates the plant's inductive defense system and enhance the resistance to pathogenic bacteria. The biochemical mechanisms of Si mainly include three aspects.