## 3 Results
### Growth Rate, Biomass Yield of Lenna minor  
This study evaluated the effects of ESS+OM; AM in ESS+OM; AM\({}_{\text{Cox}}\) in ESS+OM; AM\({}_{\text{Fe/Cuox}}\) in ESS+OM (AM in concentration 25 mg dm\({}^{-3}\)) and on Ir, Iy, FM and DM content and the results were compared with the OM-OECD (control sample). After 7 days of incubation, growth parameters were calculated from the number and area of _L. minor_ leaves. The experiment demonstrated that solution type modified the Ir, Iy and FM of _L. minor_. The addition of an electrolyte supporting solution (ESS) to the medium (OM) caused the growth rate of _L. minor_ to decrease by 24% compared to the control sample (OM), but it was not statistically significant. Meanwhile, the sample containing the dyes (AM in ESS+OM) was slightly less toxic for the tested plants, with no significant Ir = 19% growth inhibition. No phytotoxicity (Ir = 0.28%) was observed in the solution after electrooxidation using graphite electrodes (AM\({}_{\text{Cox}}\) in ESS+OM). On the other hand, _L. minor_ placed in the mixture of dyes subjected to electrooxidation conducted by means of the Fe/Cu galvanic cell (AM\({}_{\text{Fe/Cuox}}\) in ESS+OM) did not grow at all; its Ir increased significantly to 99% (Figure 5A). A similar trend as in Ir was also noted for Iy. Iy in mixtures of ESS+OM; AM in ESS+OM; AM\({}_{\text{Cox}}\) in ESS+OM and AM\({}_{\text{Fe/Cuox}}\) in ESS+OM was 36, 34, 9 and 99% respectively (Figure 5B). The FM of _L. minor_ new fronts was found to be highest (16 mg) in OM. Among the samples contaminated with dyes, the highest FM = 12.27 mg was recorded in AM\({}_{\text{Cox}}\) in ESS+OM (statistically not different from the control sample), while no new leaves appeared in AM\({}_{\text{Fe/Cuox}}\) in ESS+OM (0.37 mg); FM did not increase. At the same time, the FM of _L. minor_ growing in AM in ESS+OM was 8.88 mg, and the one exposed to ESS+OM--7.44 mg (Figure 6A). Figure 5: Inhibition of growth rate (Ir) (**A**) and inhibition in yield (ly) (**B**) of _L. minor_ exposed to OM, ESS+OM; AM in ESS+OM; AM\({}_{\text{Cox}}\) in ESS+OM; AM\({}_{\text{Fe/Cuox}}\) in ESS+OM. The data points represent the mean \(\pm\) SD, n = 6. Values are significantly different from the control at \(p\) < 0.01 (a, b). The dry matter content (DM) of the control plants (OM) was 5.62% on average. Plants growing in ESS+OM had 7.31% DM, while the DM of those exposed to AM in ESS+OM; AM\({}_{\text{Cox}}\) in ESS+OM; AM\({}_{\text{Fe/Cuox}}\) in ESS+OM had an average value of 6.15% (Figure 6B). According to the OECD [33] and ISO [34] recommendations, the toxicity of xenobotic toxicity can rely on evaluating the morphological features of _Lemma_ sp. This study examined the exposure effects of the _L. minor_ on the dyes Acid Violet 90 and Acid Red 357 in an Acid Mixture before and after using two electrooxidation types. Thus, the samples containing 25 mg dm\({}^{-3}\) the dye (AM in ESS+OM), which were not subjected to electrooxidation, had 19% growth inhibition (Ir). However, when the dyes were subjected to electrooxidation using graphite electrodes (AM\({}_{\text{Cox}}\) in ESS+OM), no phytotoxicity of these dyes was noted. (Figure 4A,B). The phytotoxicity of xenobiotics is defined as the lowest applied concentration (LOEC) of a chemical compound, reducing the measured response by more than 20% [39]. Already, a small amount of gentian violet and Congo red not electro-oxidized decreases the values of Ir and Iy by 20% already in the concentration of 0.10 and 0.64 mg dm\({}^{-3}\), respectively [40]. Dyes show different phytotoxicity. A high concentration (40 mg dm\({}^{-3}\)) of malachite green (triarylmethane dye) high (in 77%) inhibits the relative growth rate and the number of leaves (in 85%) of _L. minor_[41], while methylene blue inhibits the growth of the same plants by 46.52% [42]. Not only the type of dye but also the influence of physicochemical pretreatments applied to it affect the toxicity of dyes.