Zinc as a nutrient is used by plants in the form of Zn2+ ions.
Zinc is taken up by the plants in the form of Zn2+ ions. Zinc is a micronutrient that requires for the growth and development of plants. The concentration of Zinc required for optimum growth of plants is 20 mg/kg (weight of dry matter). Other micronutrients are Boron (B), Copper (Cu), Manganese (Mn), Molybdenum (Mo), Iron (Fe), and Chlorine (Cl). Zinc is the second most abundant transition metal present in living organisms after iron. Zinc is the only metal ion present in all six classes of enzymes. They are oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases
Zinc is an essential part of hundreds of proteins and enzymes in plants. These enzymes are responsible for catalyzing many metabolic reactions that need for the growth and development of plants. Zinc is used for the synthesis of chlorophyll pigments, conversion of starches to sugars, and the synthesis of growth hormone auxins that help in growth and elongation stem in plants.
Zinc deficiency causes chlorosis (yellowing of leaves), necrotic spots (the death of leaf tissue), rosetting of leaves, reduced growth, reduced internode elongation, and malformed leaves, etc.
Reference: Typical concentrations sufficient for plant growth. E. Epstein. “Mineral metabolism” in Plant Biochemistry (J.Bonner and J.E. Varner, eds.) pp. 438-466. (1965). Academic Press, London.