## 4 Discussion  
The plants' behavior was reported to be dose-dependent [42; 43]. The concentration of NSAIDs used in this study was chosen to be lower than the maximum values determined for the drugs found in the environmental [21; 22; 23]. NSAID-induced alterations in the photosynthetic machinery as assimilation rates and stomatal conductance to water vapor decrease for all species. A similar pattern was determined in _Lactuca sativa_ plants treated with 0.76 g L\({}^{-1}\) paracetamol [30] and in bean plants treated with 0.30 g L\({}^{-1}\) paracetamol [32]. Interestingly, there were differences in the assimilation rates for plants treated with different medicines, but no pattern could be observed. Generally, diclofenac influence lowers the carbon uptake over naproxen or paracetamol. Diclofenac's poor translocation rate to other parts of the plants could explain its low lipophilicity [44]. It has been demonstrated that reducing the assimilation rate depends on drug type and administration dose [33; 39; 45]. Such patterns have even been demonstrated in green algae, such as _S. obliquus_[45; 46], _Chlorella_, and _Desmodesinus spinosus_[47], suggesting that NSAIDs seem to impact chloroplast and mitochondrial function, resulting in lower oxygen consumption. Since all NSAIDs have the same adverse effects on the assimilation rate, all such drugs may have phytotoxicity potential. In addition, the lower activity of PSII reaction centers is probably linked to the suppression of photosynthesis. Stomata are the entry points for transpiration, photosynthesis gas exchange, and microbial penetration into the leaves of the plants. Stomatal closure is an effective defense mechanism against biotic [48] and abiotic stressors, such as drought [41; 49], ozone [50], and high temperature [51]. Moreover, many studies have shown that plants exposed to harmful metal concentrations have decreased stomatal conductance (or increased stomatal resistance). For example, stomatal conductance and density are significantly reduced in _Setaria veridis_ treated with cadmium ions [52]. In our experiment, stomata conductance to water vapor decreased for plants treated with NSAIDs. There were no clear trends for different drugs among the species. The same behavior has been found in plants treated with antibiotics but only at high concentrations [39]. This could be explained by the fact that long-distance water transport is inhibited, which results in a decrease in leaf water content and a water deficit in the leaves over time [53]. Such a decrease in stomatal conductance could be linked with the reduction of the synthesis of abscisic acid (ABA) and associated with reduced chlorophyll content [39; 54]. NSAID-induced changes in plant photosynthetic pigment content have been documented in the literature, which shows that various plant species are more or less sensitive to these drugs. Still, the pharmaceutical dosage may also play a role. Relatively low concentrations of diclofenac and naproxen determine a decrease in the total chlorophyll in the leaves of vegetables as _Atriplex patula_ L., _Spinacia olereca_ L., and _Lactuca sativa_ L. [43]. Only 2 mg L\({}^{-1}\) diclofenac determines a drop in the maximum quantum efficiency of PSII and the activity of PSII and a decrease in the content of the photosynthetic pigments for maize (_Zea mays_ L.) and tomato (_Solanum lycopersicum_ L.) plants [55]. Reduced levels of photosynthetically active pigments in plants under NSAIDs stress are directly linked to lower photosynthesis intensity levels and lower carbon uptake [56]. An alteration in the chlorophyll a/b and carotenoid/total chlorophyll ratios may indicate a reduction in PSII light-trapping activity and the initiation of antioxidant response. Non-stressed plants from the _Fagaceae_ family do not produce monoterpenes. In contrast, many plant species have monoterpenes in response to environmental stressors [57; 58; 59], and the stress-induced monoterpene emissions correlate with terpenoid gene transcription initiation [60].