# Biochemistry of Terpenes and Recent Advances in Plant Protection
## 3 Role of terpenes in Plant Protection
### Alleleptathic Activities of Trepenes in Agriculture
Momilactone inhibitory function in barnyard grass is linked to miRNA expression changes, which act as a hormonal signal transducer, DNA repairs by nucleotide excision, and the peroxisome proliferatorator-activated receptor pathway (PPAR pathway), and the p53 signaling pathway [120]. In another study, when momilactone A or B were sprayed on Arabidopsis, cruciferin 2 and 3 and cruciferina proteins responsible for providing the primary nitrogen for seed germination were highly expressed. Momilactone inhibiting cruciferins and cruciferina degradation might have consequently inhibited the germination of the Arabidopsis seeds. Moreover, the accumulation of amyrin synthase LUP2, \(\beta\)-glucosidase, a subtilisin-like serine protease, and malate synthase after momilactone treatment resulted in inhibited germination of Arabidopsis [118]. Allebotathy is illustrated in Figure 5c and Table 3. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Name of Terpene** & **Plant** & **Activity** & **Reference** \\ \hline Eucalypt & Oak & Attracts cockchafer larva & [121] \\ \hline Rhizathalene A & Arabidopsis & Resistance of the roots to the herbivore & [122] \\ \hline Eugenol, cyanophyllene oxide, \(\alpha\)-pinene, \(\alpha\)-humulene, and \(\alpha\)-phellandrene & Cinnamon and clove & Secret toxic terpenes to deter the adult pest of _Sitophilus granaries_ (grain weevil) & [123] \\ \hline \(\beta\)-Pinene & _Citrus paradisix, Poncinirus trifoliata_ & Attracts entomopathogenic nematodes, e.g., _Steinerenua diappresi_ & [124] \\ \hline S-methyl methionine & Lecythidaceae & Deters oviposition sites-seeking beetle & [125] \\ \hline \multirow{2}{*}{1,8-cineole} & Brassica & Attracts egg-laying parasitoids to the caterpillars & \\  & Tropical orchids & of feeding herbivores. & [126] \\ \hline \(\beta\)-trans-ocimene, (+)-R-limonene & Lavender & Deters pests, e.g., aphids & [127] \\ \hline \(\beta\)-costic acid & _Zaa mays_ & Inhibits the growth of _Diabrotica halteta_ & [128] \\  & & (cucumber beetle) & [128] \\ \hline \(\beta\)-ocimene & Tomato and tobacco & Defense against pests, e.g., _Macrosiphum_ & [129] \\  & & _eulphorie_ (potato aphid) & [130] \\ \hline Decanal & _Zaa mays_ & Enhanced resistance against _Ostrinia nubilalis_ & [130] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Insecticidal Activities of Terpenes. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Name of Terpene** & **Plant** & **Activity** & **Reference** \\ \hline \(\alpha\)-Terpinene Terpinen-4-ol \(\alpha\)-Thujene & _Oryza sativa_ & Antibacterial activity on Xoo & [131, 132] \\ \hline Linalool & _Oryza sativa_ & Antibacterial activity on Xoo & [133] \\ \hline epoxydolabranol & _Zea mays_ & Defense against _F. verticilloides_ and _F. graminearum_ & [101] \\ \hline Kauralexin A3 and B3 & _Zea mays_ & Antifungal activity against _R. microsporus_ and _C. graminicola_ & [134] \\ \hline \(9\beta\)-Pimara-7,15-diene-3\(\beta\),6\(\beta\),19-triol & Rice leaves & Weak antimicrobial & [99] \\ \hline Marneral & _A. thaliana_ & Pathogenesis activities & [135] \\ \hline Cucurbitaleno & _Cucumis sativus_ & Pathogenesis and insecticidal activities & [136] \\ \hline \multirow{2}{*}{Oryzaa A–F} & _Oryza sativa_ & Antimicrobial (Inhibits spore germination and the _Lersia perrier_ & [24, 99, 136] \\  & _Oryza sativa_ & Antifungal activities _M. oryzae_ and _R. Solani_ & [99] \\ \hline \multirow{2}{*}{Oryzaalexia S} & _Oryza sativa_ & Antifungal activity & [137] \\ \hline Momilactone A, momilactone B, & _Oryza sativa_ & Antimicrobial activities & [138] \\ \hline Tirucalla-7, 24-dien-3b-ol & _A. thaliana_ & Pathogenesis-related activities & [139] \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Antimicrobial (Phytoalexin) Activities of Terpenes.