AimsArsenic is a nonessential element for plants; however, high levels of As can inhibit plant growth. The toxicity of As is influenced mainly by its speciation in soil. The objectives of the present study were to determine the fractional composition of As in soil, its accumulation in plants, and its potentially toxic effects on the morphological, anatomical, and ultrastructural levels.MethodsIn a model experiment, barley (Hordeum sativum L.) was planted in Haplic Chernozem spiked with three different concentrations of As (20, 50 and 100 mg/kg). The fraction composition of As in the experimental soil was analysed using a method of sequential fractionation. The phytotoxic effects of As were analysed microscopically at the tissue, cellular, and intracellular levels.ResultsAnalysis of the fraction composition of As revealed a higher amount of mobile forms of As that contaminated the generative organs of plants. Oxides of Fe, Al, and Mn became the main soil components to retain As when contamination of As increased. Arsenic toxicity inhibited plant growth by affecting morphological parameters (shape, size, and colour). It caused impairment in the root cells and a reduction in the size of the chlorophyllic parenchyma in the leaves. The ultrastructural analysis found changes in the main cellular organelles (chloroplasts, mitochondria, and peroxisomes).ConclusionsThe bioconcentration factor (BCF), bioaccumulation factor (BF-soluble), and translocation factor (TF) allowed evaluation of plant protection mechanisms and determination of hazardous concentrations of As in soil. Despite the high buffering capacity of the soil, high As concentration affected morphological and ultrastructural parameters of the H. sativum.