Which micronutrient is required for splitting of water molecule...

Micronutrients or trace elements, are needed in very small amounts. These include iron, manganese, copper, molybdenum, zinc, boron, chlorine and nickel.

Manganese is absorbed in the form of manganous ions (Mn²⁺). It activates many enzymes involved in photosynthesis, respiration and nitrogen metabolism. The best-defined function of manganese is in the splitting of water to liberate oxygen during photosynthesis.