Selenite-induced nitro-oxidative stress processes in Arabidopsis thaliana and Brassica juncea

Extremes of selenium (Se) exert toxic effects on plants' physiological processes; although plant species tolerate Se differently. This study focuses on the effect of Se (0, 20, 50 or 100 mu M sodium selenite) on secondary nitro oxidative stress processes mainly using in situ microscopic methods in non-accumulator Arabidopsis thaliana and secondary Se accumulator Brassica juncea. Relative Se tolerance or sensitivity of the species was evaluated based on growth parameters (fresh and dry weight, root growth) and cell viability. Besides, selenite-triggered cell wall modifications (pectin, callose) and stomatal regulations were determined for the first time. In case of Arabidopsis, relative selenite sensitivity was accompanied by decreased stomatal density and induced stomatal opening, callose accumulation, pronounced oxidative stress and moderate nitrosative modifications. In contrast, the selenite-treated, relatively tolerant Brassica juncea showed larger number of more opened stomata, pectin accumulation, moderate oxidative and intense nitrosative stress. These suggest that selenite tolerance or sensitivity is rather associated with oxidative processes than secondary nitrosative modifications in higher plants.