Arsenic and antimony are well known toxic metalloids in the environment. The main goal of this work was to evaluate the effects of arsenic and antimony on the growth, anatomy, and morphology, and cell development of cultural plants. We have focused on the analysis of the negative effects of these metalloids on the roots of maize (Zea mays L.), mainly on its primary roots. Plants have been cultivated in hydroponic solutions with the increasing concentrations of tested metalloids, which correlated well with the intensity of each observed toxic effect of arsenic or antimony on the primary roots. We used the software analysis to analyse the morphological features of roots. Using light microscopy and software analysis we determined the anatomical characteristics focused on the tissue and cell level. By fluorescence microscopy we observed the development of the cell wall modifications in the endodermis and exodermis of primary root. Spectrophotometrically we determined the concentration of anthocyanins and using light microscopy we observed their location and visual difference. The most important outcomes were a reduction in the length of the primary roots even at the metalloids concentration of tenth of micromoles; changes in the area and the number of cells in each plant tissue, measured at the level perpendicular to the axis of the roots. Moreover, we observed both the changes of the anthocyanin concentration or their intracellular location in the whole root system. Additionally, the presence of both metalloids resulted in the changed cell wall composition. Predominantly, the deposition of material of apoplasmic barriers occured into the cell walls of cortical cells of the primary roots. We also observed the ontogenetic changes of endodermal and exodermal cells of primary roots dependent on the applied concentration of arsenic and antimony.

Conclusion: The plant roots are sensitively responding even to very low concentrations of arsenic and antimony. The morphological reactions are complex on the level of cells, tissues and organs and further investigation will be needed to understand the control network system maintaining the homeostasis of the whole plant after influence of toxic metalloids.

This work was supported by the Scientific Grant Agency of Slovak Republic VEGA 1/0605/17, by the Slovak Research and Development Agency under the projects APVV-15-0156 and APVV-17-0164, and by the Ministry of Education, Science, Research and Sport of the Slovak Republic under the scheme of Excellent Teams of the Slovak Republic for the Team of Experimental Plant Biology.