## 2 Phytotoxic Effects of Volatile Terpenes from the Lamiaceae Family
The EO of _Mentha_\(\times\)_piperia_ L., which is rich in mentone, menthol, and menthofuran, has been shown to strongly inhibit seed germination and seedling growth in three weed species: field bindweed (_Convolvulus arrensis_ L.), purslane (_Portulaca oleraca_ L.), and jungle rice (_Echinochloa colona_ L.), as well as two horticultural crops, tomato (_Lycopersicon esculentum_ Mill.) and radish (_Raphanus sativus_ L.) [67]. The monoterpenciords carvacrol and thymol, found in the EO of _Origanum acutidens_ L., completely inhibited seed germination and seedling growth in three weed species: _Amaranthus retroflexus_ L., _Chenopodium album_ L., and _Rumex crispus_ L. [68]. The main constituents of _Salvia sclarea_ L. EO, the monoterpenes L-linalool, linalyl acetate, \(\alpha\)-terpineol, and geraniol showed a strong inhibitory effect on the seed germination of _L. sativum_, _L. sativa_, and _P. oleraca_[69]. [PERSON] et al. [70] investigated the phytotoxic effects of thirteen EOs derived from six wild Lamiaceae species: _Clinopodium suaveolens_ L., _Satureja montana_ L. subsp. _montana_, _Thymus capitata_ (L.) Cav., _Salvia fruticosa_ Mill. subsp. _thomasii_, _Satureja cuneifolia_ Ten., and _Thymus spinulos_ Ten. The study assessed their impact on the seed germination of _L. sativum_ and _Phelipanche ramose_ L. seeds, the elongation of _Solanum lycopeneum_ L. radicles, and the chlorophyll (Chl) and carotenoid content in _C. album_ leaves. Notably, the EO from _T. capitata_ inhibited _L. sativum_ seed germination and significantly reduced Chl and carotenoid levels in _C. album_. Additionally, the EO from _T. spinulos_ suppressed _S. lycopeneum_ radicle elongation. The observed phytotoxic effects were associated with key EO components such as thymol and \(p\)-cymene, highlighting their potential application as pre-emergence herbicides. [PERSON] et al. [71] investigated the phytotoxic effects of _Hysospus officinalis_ L. EO on the seed germination and seedling growth of two weed species (_Setaria viridis_ L. and _Sorghum halepense_ (L.) Pers.) and two vegetable crops (_L. sativa_ and _Spinacia olerca_ L.). The EO, characterized by high levels of _cis_-pinocamphone, _trans_-pinocamphone, and \(\beta\)-pinene, exhibited species- and concentration-dependent effects, either inhibiting or promoting seed germination and growth. Cineole and citronellol, commonly found in plants of the Lamiaceae family, significantly inhibited seed germination, reduced seed germination rates, suppressed seedling growth, and reduced the Chl content and respiratory activity of a noxious weed--_Agentum coryzoides_ L. [72]. Furthermore, the EOs of _O. vulgare_ ssp. _hitrum_, rich in monoterpenes such as carvacrol, thymol, and ocymene, significantly reduced _A. thaliana_ growth, causing leaf chlorosis and metabolic disruptions, especially nitrogen assimilation, through glutamine metabolism, which led to toxic ammonia accumulation,oxidative stress, reduced photosynthetic efficiency, and photorespiration [73]. [PERSON] et al. [74] revealed the different phytotoxic effects of two volatile monoterpene isomers, 1,4-cineole and 1,8-cineole, which have the same molecular formula (C\({}_{10}\)H\({}_{18}\)O) but differ in the position of their oxygen bridges. Despite their structural similarity, the isomers showed different biological activities in two tested weeds, the monocot _Echinochla crus-galli_ (L.) [PERSON] and the dicot _Cassia obtusifolia_ L. 1,4-Cineole inhibited root and shoot growth, led to morphological distortions, and caused significantly greater photosynthetic stress, while 1,8-cineole primarily reduced root growth and seed germination rates. Analysis of the mitotic index revealed that 1,8-cineole suppressed all stages of mitosis, while 1,4-cineole only caused a reduction in the prophase stage compared to the controls.