Explanation

Fe is an important constituent of proteins which is involved in the transfer of electrons like ferredoxin and cytochromes. It is reversibly oxidised from $Fe^{2 +}$ to $Fe^{3 +}$ during electron transfer. Cu It is essential for the overall metabolism in plants. Like iron, it is associated with certain enzymes involved in redox reactions and is reversibly oxidised from Cu to $Cu^{2 +}$