Morphogenic responses of the roots of Arabidopsis thaliana (Magnoliophyta: Brassicales) to Cr(VI) stress

The growth response of roots to stress conditions is a strategy that allows the plant to either avoid the adverse conditions or to adapt to them. Human activities have resulted in the accumulation of some metals from certain concentrations have an adverse effect on plant growth. Among these, Chromium (Cr) is a serious pollution caused by metal processing industries and leather tanning. To understand in detail the response of roots Cr(VI) stress, it was used an in vitro system with Arabidopsis thaliana utilizing three experimental conditions. (A) Plants germinated and grown for 6 days, without lateral roots, were transferred to media with different concentrations of Cr(VI). This allowed the evaluation as affecting the growth of the primary root to move quickly from MS medium to MS medium with Cr(VI) and the extent to which stimulated or inhibited the formation and growth of new lateral roots. (B) Plants germinated and grown for 8 days, with lateral roots, transferred to media with different concentrations of Cr(VI). This condition allowed us to evaluate how they affected the growth of primary roots and lateral roots previously formed to move quickly from MS medium to media supplemented with Cr(VI). In addition, it was possible to compare how new lateral roots behave. (C) Seeds germinated directly on MS medium with Cr(VI) diffusion, which allowed us to determine how they affected the growth of primary and lateral roots gradually passing from one medium to another MS supplemented with Cr(VI). The results obtained showed that (a) stress tolerance was greater when plants were grown in a gradient from low to high concentration of Cr(VI), (b) the plants were more tolerant to stress with further development of these, and (c) lateral roots formed when the plant was in the medium with the metal, were always more tolerant than the primary root and lateral roots previously formed.