## 2 Phytotoxic Effects of Volatile Terpenes from the Lamiaceae Family
### The Biological Activity of Essential Oils Is Determined by the Stereochemistry of Nepetalactones
[106] found that \(\alpha\)-pinene increased POX activity in _Cassia occidentalis_. Although CAT activity in ragweed shoots showed no significant change in response to treatments with _N_r_EO or _Nc_EO_, POX appears to be the major enzyme responsible for the degradation of H\({}_{2}\)O\({}_{2}\)[37]. In addition, the phytotoxic effects of monoterpenoids could be related to the disruption of cell membranes and the associated enzymes [95; 113]. It has been demonstrated that \(\alpha\)-pinene and limonene can cause phytotoxicity to mitochondrial respiration in the hypocotyls ofsoybeans (_Glycine max_ (L.) Merr). The results suggest that \(\alpha\)-pinene acts on mitochondria isolated from the coleoptiles and primary roots of maize (_Zea mays_ L.) via at least two mechanisms: uncoupling of oxidative phosphorylation and inhibition of electron transfer. Confirming the disruption of mitochondrial energy metabolism, \(\alpha\)-pinene strongly inhibited mitochondrial ATP production [114; 115]. [PERSON] et al. [37] demonstrated that in ragweet shoots, \(Nr\)EO and \(Nc\)EO stimulated POX activity, while CAT and superoxide dismutase (SOD) were inhibited, which is consistent with previous findings showing that monoterepenes inhibit SOD [106; 116]. [PERSON] et al. [35; 36] also demonstrated that VOCs released from the shoots of \(N\). _tranjensis_ and \(N\). _sibirica_ L. significantly reduced the seed germination and growth of garden cress (_Lepidium sativum_ L.) seedlings. The dominant compound in the atmosphere of the \(N\). _tranjensis_ vessel was _trans,cis_-NL, while in the \(N\). _sibirica_ vessel, _cis,trans_-NL predominated. The _trans,cis_-isomer showed a significantly stronger inhibitory effect on the seed germination of garden cress than _cis,trans_-NL. The phytotoxic effects of NL are mainly observed through its influence on various biochemical processes that disrupt the plant's antioxidative system. These perturbations lead to the inhibition of important enzymatic activities, including POX and CAT, which are crucial for the mitigation of oxidative stress. In addition, alterations in the profiles of Fe- and Cu/Zn- isoforms of SOD were detected, further highlighting the altered ability of seeds to neutralize ROS associated with VOCs, in which NL predominates. To further investigate the phytotoxic effects of VOCs from \(Nr\)EO, an in vitro system in which seeds were exposed to VOCs in the ambient atmosphere of Petri dishes was established [38]. Species-specific and dose-dependent effects of \(Nr\)EO were observed. Among the crops tested, _L. sativa_ was the most sensitive, while _B. napus_ showed the highest tolerance to both the \(Nr\)EO and the pure monotereponds (\(\alpha\)- and \(\beta\)-pinene). Among the weeds, _S. media_ was the most sensitive, while _R. crispus_ showed the highest tolerance. Of the two monoterepens, \(\alpha\)-pinene exhibited greater phytotoxicity than \(\beta\)-pinene and particularly affected the seed germination of _L. sativa_, _L. corniculatus_, _B. napus_, and _S. media_. This differs from the results of [PERSON] et al. [117], who found that \(\beta\)-pinene had a stronger inhibitory effect on the seed germination of _Brassica campestris_ L. seeds, while \(\alpha\)-pinene showed no effect on seed germination but later inhibited root growth. In addition, [PERSON] et al. [118] found that \(\alpha\)-pinene inhibited both seed germination and primary root growth in _Zea mays_. Furthermore, [PERSON] et al. [119] attributed the phytotoxic effects of the EOs of _Laminum purpneum_ L. and _Lamin amplexaic_ L. to their main constituents \(\alpha\)-pinene and \(\beta\)-pinene. [PERSON] [101] demonstrated the phytotoxic effect of the EO of \(N\). _nuda_ L. subsp. _albifora_, which contains _trans,cis_-NL as its dominant compound. The major compound of _Nepeta flavida_ Hub.-Mor. EO, 1,8-cineole, exhibited phytotoxic effects on seed germination and radicle and plumule length in _L. sativum, Raphanus sativus_, and _Eruca sativa_ Mill. [100].