Effect of silicon on root growth, ionomics and antioxidant performance of maize roots exposed to As toxicity

Nowadays, one of the biggest challenges of plant physiology is to find out the ways how to mitigate negative impacts of abiotic stress on plants. It is the pollution of groundwater or soil by various metals and metalloids that significantly affects the quality of life. Both arsenic (As) and silicon (Si) are metalloids - while the first one is toxic in general, the latter one is considered as beneficial for plants suffering from various kinds of stresses. The aim of our work was to elucidate the growth and development of young maize (Zea mays L.) plants exposed to both of these metalloids simultaneously. Experiments were focused on the comparison of root growth and biomass allocation, changes in uptake of macro- and micronutrients, visualisation of free radicals along with monitoring of the dynamics of main antioxidant enzymes activity in roots. The results showed that increasing concentration of As (75 and 150 μM As) severely inhibited root length and the amount of biomass, and addition of Si (2.5 mM) to the medium containing As did not have a significant effect on root growth. Similarly, the application of Si did not influence the uptake of macro- and microelements into the roots (mainly Ca, P, K, Mo, Cu, Zn and Ni) which was mostly decreased due to As. On the other hand, Si significantly decreased the presence of both superoxide and hydrogen peroxide in roots that suffered from As toxicity. Although the overall growth of maize plants was not improved by Si amendment, we assume that Si might affect the functionality of key antioxidant enzymes in time, and in this way at least partially help to overcome negative effects of As on maize roots.