## 2 Materials and Methods  
The plant material was _Aldrovanda vesiculosa_ shoots with apex, collected from the Orchowe lake in East Poland, in June. The shoots were transported immersed in lake water in plastic containers. In the laboratory, the shoots were defoliated and the tip parts of 2-3 cm in length were used for the experiment. The explants were disinfected in the following steps: 1--rinse in water with a few drops of Ludwik (GRUPA INCO S.A., Warszawa, Poland), twice for 10 min; 2--dip in 70% ethanol (Chempur, Piekary Slaskie, Poland) for a few seconds; 3--disinfect with a 0.5% of sodium hypochlorite (NaOCI), (Chempur); 4--rinse 3 times in sterile distilled water and then place in a liquid media, described below. After 24 h, in the laminar flow chamber, the explants were taken out from the media and immersed for a few seconds in 0.5% NaOCI, 70% ethanol, or 0.5% NaOCI, followed by 70% ethanol. Then the explants were placed in the fresh liquid media of the same content, individually in the Erlenmeyer flasks of the 100 mL volume. Half of the media was supplemented with silver nanoparticles (AgNPs) solution (Sigma-Aldrich, Saint Louis, MO, USA, catalog no. 576832), at a concentration of 5 mg\(\cdot\)dm\({}^{-3}\).  
The media used in the experiment (1/5 MS) consisted of 5-times diluted Murashige and Skoog (MS) [36] macro- and micronutrients composition, which is the most popular media and is recognized as suitable for most plant species. The media was diluted because _Aldrovanda vesiculosa_ grows in peat bogs and lake water poor in nutrients, and, as a carnivorous plant, it is sensitive to high amounts of nitrogen.  
The medium was supplemented with thiamine (vit. B1)--0.1 mg\(\cdot\)dm\({}^{-3}\) (Sigma-Aldrich, Saint Louis, MO, USA), pyridoxine (vit. B6)--0.5 mg\(\cdot\)dm\({}^{-3}\) (Sigma-Aldrich, Saint Louis, MO, USA), niacine (vit. PP)--0.5 mg\(\cdot\)dm\({}^{-3}\) (Sigma-Aldrich, Saint Louis, MO, USA), glycine--2.0 mg\(\cdot\)dm\({}^{-3}\) (Chempur, Poland), myo-inositol--100 mg\(\cdot\)dm\({}^{-3}\) (Sigma-Aldrich, Saint Louis, MO, USA), and sucrose--20 g\(\cdot\)dm\({}^{-3}\) (Chempur, Piekary Slaskie, Poland). The media pH was established at 5.5 and steam sterilized for 21 min at the temperature of 121 \({}^{\circ}\)C and under 1 hPa pressure. The flasks with explants were placed in a growing room at the temperature of 25 \({}^{\circ}\)C with 16-h photoperiod. The sources of light were fluorescent day-light lamps with 30 \(\upmu\)mol\(\cdot\)m\({}^{-2}\cdot\)s\({}^{-1}\) light intensity (Philips TLC 58W/84).  
The experiment lasted for 8 weeks. The observations concerning the contamination rate and regeneration of the explants were performed once a week. At the end of the experiment, the following features were evaluated: the number of explants with the symptoms of contamination, the number of explants with the symptoms of necrosis, and the number of regenerating shoots. Morphological observations regarding the length of shoots, length of internodes, and length of petioles and traps, were also performed with the use of a Keyence VHX-950F stereoscopic microscope.  
The regenerated and contamination-free shoots were placed in the fresh liquid media of the same macro- and micronutrient content, but without the addition of AgNPs, for further growth. Observations were performed after the next 8 weeks and the regenerated shoots were again placed in the fresh media. Passages were completed every 8 weeks, as it was the time when the regenerating shoots were long enough to be divided. Each time, only the green parts were used.