## 3 Results
### Growth Rate, Biomass Yield of Lenna minor
During the process of electrooxidation, the iron ions are released from the electrode to the medium. These ions can be phytotoxic. Water plants _S. polyrrhiza_ (L.) [PERSON] after 24 h treatments of 100 mg dm\({}^{-3}\) Fe accumulated 6.84 mg g\({}^{-1}\) of these ions in the DW. Due to accumulation, it has been observed that fronts are dark brown and necrotic or dead [43]. Iron oxide nanoparticles are also highly toxic to aquatic plants. According to the authors, iron oxide in concentrations \(\geq\)30 mg dm\({}^{-3}\) kills _L. minor_ within 7 days. The authors also report that lipid peroxidation in the tissues increased with increasing iron oxide nanoparticles concentration, the chlorophyll content decreased at 50 mg dm\({}^{-3}\) of iron oxide nanoparticles and Fe\({}^{3+}\) accumulation in _L. minor_ roots, which can inhibit nutrient uptake [44]. In this study, the mixture of dyes (25 mg dm\({}^{-3}\)) was subjected to electrooxidation with the use of an iron anode and a copper cathode (AM\({}_{\text{Fe/Cuox}}\) in ESS+OM) was lethal for _L. minor_ (Figure 4A,B). The same effect (Ir = 100%) causes 12 mg dm\({}^{-3}\) of gentian violet--an aniline-derived triphenylmethane dye [45; 46]. Congo red--a benzidine-derived azo dye in the same concentration, inhibits plant growth by half (Ir = 50%) [40]. Plant growth inhibition results in a reduction in FM (total wet weight) of _L. minor_. The reduction in FM due to exposure to Direct Red 28 was reported by [PERSON] et al. [47], under the influence of  
Figure 6: Fresh mass (FM) (**A**) of new fronts, dry matter content (DM) (**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–d). gential violet and Congo red [40]. In addition, the tested dyes decreased the FM (total wet weight) of _L. minor_. Xenobiotics in high concentrations in water manifest in the form of hypertonic and hyperosmotic stress, which results in dehydration of _L. minor_ tissues and an increase in DM [48]. When the osmotic pressure in plants decreases, they are unable to take up the water, which results in stomata closing and a drop in turgor pressure. The dyes caused membrane disintegration, dehydration of tissues, and a systematic increase in DM, which reached an average of 6.15% in plants exposed to AC (AM in ESS+OM; AM\({}_{\text{Cox}}\) in ESS+OM; AM\({}_{\text{Fe/Cuox}}\) in ESS+OM). Meanwhile, DM in the control plants (OM) was determined to be 5.62% (Figure 6B). However, when the FM of common wheat seedlings (_Tritcium aestivum_) decreased in a study by [PERSON] and [PERSON] [49], then the textile dyes had no effect on DM. These findings imply that among the studied samples, the untreated (AM in ESS+OM) and those subjected to electrooxidation with the use of an iron anode and a copper cathode (AM\({}_{\text{Fe/Cuox}}\) in ESS+OM) were the most phytotoxic for _L. minor_ and the least were those where electrooxidation was carried out using graphite electrodes (AM\({}_{\text{Cox}}\) in ESS+OM). High concentrations of raw malachite green [50] and Brilliant Blue R [51] were also the cause of the strongly reduced growth of _L. minor_. Raw Congo red at a concentration of 2500 ppm totally inhibited the growth of _L. minor_[47]. Nevertheless, the inhibition of plant morphological features is a secondary toxicity effect of xenobiotics. [PERSON] et al. [52] also observed that the growth rate was an indirect marker of dyes' toxicity to _L. minor_. It is concluded that xenobiotics also decrease the FM of plants, inhibit the chlorophyll biosynthesis pathway [53; 54; 55] and limit photosynthesis, thus reducing the yield. Hence, the supposition is that the inhibition of the plant growth rate is the result of chlorophyll degradation at the photosynthetic apparatus level. In the present study, the leaves exposed to the dyes were not green, as the pigments were transferred to the tissues (Table 4). Dyes in the _L.