The sweet side of misbalanced nutrients in cadmium-stressed plants

Some plants are able to maintain or improve their performance under cadmium (Cd) exposure, despite high Cd concentrations in roots and shoots, indicating that they have protective strategies to neutralise the side effects from Cd accumulation. The regulation of antioxidant machinery and the mitigation of Cd uptake and translocation have been the focus of several studies, but evidence shows that the modulation of nutritional status is also involved in tolerance mechanisms. Although alterations in the nutrient concentrations are usually coupled to negative outcomes on the development of plants under Cd exposure, current works have shown their "sweet" sides. Here, we provide evidence that the degree of plant tolerance to short Cd exposure is, at least partially, associated with differential changes in magnesium (Mg), manganese (Mn) and boron (B) status, all of which modulate physiological and developmental events, such as root architecture (Mg and/or B status), ionomic balance (Mn and/or B status), biomass production (Mg and/or Mn status) and biomass allocation (Mg/K ratio). Modulation of root architecture can be a strategy to obtain water and nutrients in metal-free patches in a growing medium. Changes in the uptake and/or distribution of nutrients may adjust the ionomic profile to equilibrate charge and pH homeostasis after Cd entrance into the plant. Alterations in the Mn and Mg status may alter the balance between photorespiratory and photosynthetic metabolisms. Finally, reprogramming biomass allocation among organs can be a strategy to remodelling plant body in order to better cope with environmental challenges. The identification and understanding of plant tolerance mechanisms against heavy metal toxicity is necessary to support strategies to mitigate their impacts on crop productivity and quality, supporting food security in increasing environmental contamination in the Anthropocene.