Figure 2.

Schematic illustration of cobalt (Co²⁺) absorption, transport, and distribution in plants. Co²⁺ is absorbed from the soil into epidermal cells of roots by an iron transporter (IRT1). Once Co²⁺ is absorbed inside cells, Ferroportins (FPN1 and FPN2) are responsible for its further movement. FPN2 transports Co²⁺ into vacuoles, resulting in the sequestration of Co in root cells. FPN1 is to load Co²⁺ into the xylem. In the xylem, Co²⁺ is complexed with citrate, histidine (His), methionine (Met), or nicotianamine (NA) to be translocated to shoots. Co²⁺ is released in leaves and participate in metabolisms, which are often associated with nickel (Ni) and iron (Fe). It is shown here the Ni and Co movement in or out of chloroplasts through ATP-binding cassette (ABC) transporter in the mediation of ionic homeostasis in the chloroplast.