What is the number of the absolutely essential elements for growth and metabolism of all plants?

The macronutrients include carbon, hydrogen, oxygen, nitrogen, phosphorous, sulphur, potassium, calcium and magnesium. Micronutrients include iron, manganese, copper, molybdenum, zinc, boron, chlorine and nickel. C, H, O, N, P, K, Ca, Mg, S, Fe, Mn, Mo, Cu, Zn, Cl, Ni, B are 17 elements absolutely essential for plant growth and development.