## 1 Introduction  
Plant protection products, also referred to as pesticides, are widely used in agriculture in order to improve productivity, prevent crop loss or yield reduction, and control disease vectors or agents. However, it is known that only a small portion of the applied pesticides reach the target pests, while the remainder will end up in soil or will have the potential to move to other environmental compartments, including ground and surface waters [1; 2]. Nevertheless, the mobility of these contaminants in the environment depends on several biotic and abiotic variables, and their physical-chemical properties. Thus, depending on the persistence of each substance, soil contamination can occur, thereby affecting soil quality, compromising its ability to perform its functions and leading to an irreversible degradation of this non-renewable resource [3; 4; 5; 6; 7]. For this reason, concerns about the use of pesticides are increasing, and the most controversial at the moment is probably glyphosate (GLY), a post-emergence and systemic herbicide of broad spectrum (non-selective). Applied to the foliage of weeds, GLY is absorbed by the leaves and is rapidly translocated in the plant through the phloem, particularly accumulating in meristems (root and shoot apex). Right after its discovery in the 1970s, GLY quickly became the most applied herbicide worldwide and, in 2014, the volume applied was sufficient to treat between 22% and 30% of globally cultivated cropland [8]. Despite its great efficiency, several concerns about this herbicide were recently raised, related to the divergence between scientific studies regarding its toxicity to non-target organisms [9; 10]. Another factor that may turn difficult to evaluate the real impacts of GLY on the environment is that GLY commercial formulations not only contain GLY, but also substances such as polyethoxylated amine (POEA) surfactants [11]. It is known that the first generation of POEA surfactants present in Roundup(r) were markedly more toxic than GLY, but since the mid-1990s, these compounds were progressively replaced by other POEA surfactants, ethoxylated etheramines, which exhibit lower non-target toxic effects [11]. However, the composition of non-active ingredients in a GLY-based herbicide (GBH) is not fully known, and while a recent study pointed to a lower toxicity for earthworms of the GBH compared with the active ingredient (a.i.) itself, [PERSON] et al. [9] in another study concluded the opposite regarding _Dimorphandra wilsonii_ seed germination [12]. Thus, GLY can be considered an old pesticide, but an emergent problem. In areas in which high extensions of land are dedicated to intensive agriculture, the dispersion of GLY in the environment can be a serious problem of diffuse contamination, particularly due to its tendency to adsorb to solid particles [13; 14]. Depending on climatic conditions (especially temperature and humidity), the removal of GLY from soils can be reduced, resulting in its accumulation [15]. This accumulation and dispersion through the environment, due to its non-selectivity [16; 17], can cause damage to plants that are not targeted, affecting a great number of species that account both directly and indirectly for soil biodiversity. From the available data, it was suggested that GLY negative effects on plant growth and development substantially exceed the effects triggered by its mode of action as it can induce several metabolic and physiological disorders, favoring the occurrence of oxidative stress as an indirect consequence [18]. Indeed, when plants are exposed to stress factors, such as soil contamination, oxidative stress occurs due to an overproduction of reactive oxygen species (ROS) [19; 20]. Therefore, given their higher sensibility, ROS, along with oxidative stress parameters (e.g., lipid peroxidation), can be used as exposure biomarkers, allowing an early warning and sensitive evaluation of plant physiological status, representing a potential tool to phytotoxicity studies [21].