Mn and Cl are essential elements for the photolysis of water during photosynthesis. Ca is associated with the growth of the plant and is required by meristematic and differentiating tissues. Potassium helps to maintain an anion-cation balance in cells and is involved in protein synthesis, opening and closing of stomata, activation of enzymes and in the maintenance of the turgidity of cells. Zn and Cu are essential in maintaining the metabolism in plants. Zn activates various enzymes, especially carboxylases. It is also needed in the synthesis of auxins. Cu is involved in redox reactions. N and P are important for the overall development of plants in crop production. They are major constituents of many biomolecules.