## 1 Introduction  
_Aldrovanda vesiculosa_ L. (Drosearaceae), a waterwheel, is a carnivorous water species endangered by extinction all over the world, and it is under protection in all European countries. One of the biggest populations of the species is located in East Poland. Unfortunately, the number of natural stands and populations of Aldrovanda has decreased, both in Poland and worldwide [1]. According to [PERSON] [2], in 1987, there were 14 confirmed localities of the waterwheel and, nowadays, there are only six left. The author investigated the factors affecting the survival of aldrovanda in the temperate climate of Poland, and suggested that the species should be reintroduced into new, better, and substitute localities. _Aldrovanda vesiculosa_ does not form mature seeds in the Polish climate; therefore, it may be propagated only vegetatively. As the number of existing donor plants is low, it is important to use the methods which are the least harmful to the plants. Propagation in vitro allows for the production of the critically endangered plant species, as it allows us to obtain a lot of good quality and healthy plantlets, with no harm to the mother plants. Tissue culture has been commonly used for the propagation of many rare and endangered plant species [3, 4, 5]. There is little information on the micropropagation of _A. vesiculosa_. [PERSON] et al. [6] described the disinfection method and initiation of the aldrovanda cultures from seeds of the Japanese race of the species. The authors disinfected seeds with 1% benzalkonium chloride, sodium hypochlorite, and ethanol. The seeds were placed in B5 Gamborg liquid medium with 2% sucrose, the addition of 20-50 mg-dm\({}^{-3}\) of gibberellic acid, and a few drops of antibiotic. After a day, the seeds were individually placed in the fresh medium of the same composition and kept at 22 \({}^{\circ}\)C under a light. After a week, 60% of the seeds germinated and formed shoots and proliferated. The authors managed to obtain regeneration from turions as well, but, at the same time, they stated that the growth of the Polish race is different. [PERSON] et al. [7] studied the in vitro cultivation of aldrovanda, and they proposed the media for micropropagation of the species. The authors used the plants obtained from the Kondo cultivation. The authors studied the medium for aldrovanda micropropagation and suggested that the half strength of B5 with only 500 mg-dm-3 KNO3 was the best. They attempted to initiate the cultures from seeds but stated that, due to a high contamination rate (52.3%) and low germination (44.4%), the method was not reliable. Therefore, the authors advised using defoliated shoots and mild surface sterilization. However, the method itself was not provided. Plant tissue cultures are commonly applied not only for the conservation of endangered plant species, but for wider use in the propagation of crop species, the production of bioactive compounds, or as models for scientific studies. However, to make all that possible, the plant material has to be disinfected before tissue culture initiation. That stage might decide the success of micropropagation, as only contamination-free cultures are used for further regeneration of plant material, which would lead to obtaining healthy and good quality plants. To obtain in vitro cultures free of contaminations, the plant material has to be surface disinfected. It is extremely difficult to find a balance between the use of disinfection substances strong enough to get rid of any microorganisms, and mild enough to not kill the plants. The disinfection part is also highly important because remaining microorganisms usually grow fast in tissue culture. There are many sterilizing substances used for the surface disinfection of plant material. The most often used are calcium hypochlorite (CaOCI), sodium hypochlorite (NaOCI), ethanol (EtOH), hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)), mercuric chloride (HgCl\({}_{2}\)), silver nitrate (AgNO\({}_{3}\)), fungicides, and antibiotics.