## 1 Introduction  
There is currently a risk of farmland being contaminated with potentially toxic elements (PTEs) from various sources, e.g., from the chemical and engineering industries [1, 2]. These substances represent a serious world-wide ecological problem with a negative effect on soil-plant ecosystems [3]. PTEs can be defined as a huge group of chemical substances (components of pesticides and fertilizers, including elements such as As, Cd, Pb, etc.). PTEs cause abiotic stress, which reduces plant growth. Some of the most significant PTEs are heavy metals (HM; Table A1) [1]. There is, however, a difference in the bioavailability and persistence of individual PTEs. If we, for example, compare some heavy metals and their compounds exhibiting toxicity with residues of active substances of pesticides, then differences can be found in their disintegration and mobility within the soil environment [1, 2]. Organically based PTEs can be more easily incorporated into plant and animal biomass,for example. On the other hand, HMs (As, Cd, Pb, and Zn) and their compounds exhibit a longer half-life. Moreover, HM ions are characterized by limited mobility in the soils, primarily due to binding to soil particles [1; 2; 3]. The soil is contaminated with PTEs due to anthropogenic activities such as mining and metallurgical industries, agriculture, combustion processes, etc. [4; 5]. High concentrations of PTEs are highly toxic and are considered as environment pollutants. PTEs that are taken for pollutants include As, Cu, Cd, Pb, Cr, Ni, Hg, and Zn [6; 7]. Plants uptake PTEs, similarly to nutrients, mainly by their roots from the soil [3]. The uptake of PTEs by plants has no linear dependence on the total concentration of PTEs in the soil, but rather on their availability to plants, and differs in various plant species [6; 8; 9]. These PTEs stored in plant biomass may further enter the food chain and adversely affect the health of humans and animals. For example, Pb and Hg are absorbed from plant biomass in the digestive tract of mammals and further released into the bloodstream. Pb negatively affects the hematopoietic system (anemia occurs) and nervous system. Lead also causes renal disorders and liver dysfunction [9]. Hg binds to sulfanyl groups, hence uncompetitively inhibiting a number of enzymes. The danger of PTEs resides in the risk of their accumulation in tissues and of possible poisoning by repeated accumulation [8; 9]. PTEs are accumulated particularly in roots while a much smaller amount is transported into the above-ground parts. Various plant species differ in their capacity of PTE accumulation, which is affected by root morphology [10]. Plants with a high number of fine roots can take up and accumulate a much greater amount of PTEs than plants with large-diameter roots. Heavy metals originating from non-natural sources represent abiotic stressors [11; 12]. Certain types of plants are able to cope with the stress caused by the increased concentration of heavy metals in the soil by the process of phytoremediation [1; 10; 11; 12]. Phytoremediation makes use of the notable ability of plants to concentrate elements and compounds from the environment and to metabolize various molecules in the plant tissues [12]. This process has a potential to eliminate pollutants from the environment [12]. According to [PERSON] et al. [13], phytoremediation methods can be divided into categories such as phytoextraction, phytodegradation, rhizfiltration, phytostabilization, phytovolatilization, and rhizodegradation. In this study, the potential of _Meliotus albus_ Med. for phytoextraction of PTE is researched. Phytoextraction is a method that is based on the accumulation of the molecules of heavy metals in the above-ground parts and sprouts of plants [14; 15]. Figure 1 shows the individual phytoremediation methods and the significance of processes in the plants for their realization [14]. Hyperaccumulators represent a separate chapter.