How many of the following statements describing the functions of Mn are true? I. Mn is required during non-cyclic photophosphorylation. II. Mn competes with iron and magnesium for uptake. III. Mn promotes calcium translocation in the shoot apex. IV. Mn is an activator of many respiratory enzymes.

Step-by-step solution

Manganese is absorbed in the form of manganous ions. It activates many enzymes involved in photosynthesis, respiration and nitrogen metabolism. It is involved in photolysis of water during non-cyclic photophosphorylation to liberate oxygen during photosynthesis. Manganese competes with iron and magnesium for uptake and with magnesium for binding with enzymes. Manganese inhibits calcium translocation in shoot apex.