## 4 Discussion
However, and regarding the former hypothesis, this does not mean that an enhanced effect on a natural soil with a more diverse and functionally active soil microbial community would certainly be expected, as the degradation rates of both GLY and AMPA are still not well studied. As important as photosynthesis, the mineral nutrition of plants highly contributes to proper growth performance. However, the effect of GLY on plant mineral nutrition is yet to be fully understood [78]. Up to now, no consensus has been reached on the influence that GLY may bring on nutrient uptake, since the studies conducted so far point towards different result. While several authors reported a negative effect of GBH on plant's nutrient uptake [78; 79; 80; 72], other studies concluded that this application does not affect the mineral status of the plants [81; 82; 83]. As reviewed by [PERSON] et al. [83], these inconsistent results may be due to differences in the type of soil, climatic conditions, and/or GLY-resistant cultivars used. Aiming to assess the nutritional status of _M. sativa_ under GLY exposure, the present study evaluated the activity of GS, an enzyme that is involved in the first step of ammonium (NH4\({}^{+}\)) assimilation, not only that which is absorbed by roots, but also the one generated from photorespiration, proteolysis and processes that are increased by several stresses [84; 85]. The results revealed that GS was dysregulated for almost all tested concentrations, indicating that, at least under the experimental conditions of the present work, GBH interfered with nitrogen (N) metabolism. Based on these findings, the hypothesis that GLY conditioned the physiological uptake of mineral nutrients, especially nitrogen (N), due to the formation of complexes making them unavailable for biological processes, arises [86]. Concerning N uptake, once again, results from different studies, all of them using GBH, are contradictory with no effect in field studies [87; 88] and inconsistencies in greenhouse studies [78; 79]. As previously reviewed by [PERSON] and [PERSON] [22] and [PERSON] et al. [20], plant development can be severely affected by various abiotic stressors, such as herbicide application, leading to an overproduction of ROS which, in its turn, will cause significant damage to cell structures, ultimately resulting in oxidative stress. In order to verify the occurrence of oxidative stress, H\({}_{2}\)O\({}_{2}\) levels and LP degree, as a means to assess membrane damage, were evaluated. According to the results obtained, H\({}_{2}\)O\({}_{2}\) accumulation was enhanced upon exposure to GBH, especially at levels of the a.i. higher than 12 mg kg\({}^{-1}\). However, when looking to LP results, MDA content was only increased in response to the two highest treatments (26 and 40 mg kg\({}^{-1}\) of a.i.). Based on this behavior, one can suggest that ROS overproduction took place earlier than the observed membrane damage, this being possibly related to the dual role played by ROS in plant cells. Indeed, H\({}_{2}\)O\({}_{2}\), as with other ROS, can act as a signal molecule at low concentrations as it is involved in acclimation signaling, leading to plant tolerance to various biotic and abiotic stresses, becoming toxic above a certain threshold, capable of inducing programmed cell death [89]. Therefore, it can be hypothesized that, at lower GLY concentrations, H\({}_{2}\)O\({}_{2}\) was involved in signaling mechanisms (with no LP increase), while at the highest concentrations (26 and 40 mg kg\({}^{-1}\) of the a.i. ), H\({}_{2}\)O\({}_{2}\) accumulation started to induce oxidative damage, which is reflected by the occurrence of LP. The induction of oxidative stress by GLY is described as one of its indirect effects on plant physiology, either by the overproduction of ROS or by a depletion of defense mechanisms [50].