Macro-Nutrients	Symbol	From Avail to Plants	Function in Plants
Nitrogen	N	NO3-, NH4+	Component of amino acids, proteins, nucleotides, nucleic acids, chlorophyll, and coenzymes
Phosphorus	P	H2PO4-, HPO4 2-	Component of energy-carrying phosphate compounds (ATP and DTP), nucleic acids, several coenzymes, phospholipids
Potassium	K	K+	Involved in osmosis and ionic and in opening and closing of stomata, activator of many enzymes
Calcium	Ca	Ca2+	Component of cell walls, enzyme cofactor, involved in cellular membrane permability, component of calmodulin, a regulator of membrane and enzyme activities
Magnesium	Mg	Mg2+	Component of the chlorophyll molecule, activator of many enzymes
Sulfur	S	SO42-	Component of some amino acids and proteins and coenzyme A
Iron	Fe	Fe3+, Fe2+	Required for chlorophyll synthesis, component of cytochromes and nitrogenase
Boron	B	H3BO3	Influences calcium utilization, nucleic acid synthesis, and membrane integrity
Copper	Cu	Cu+, Cu2+	Activator or component of some enzymes involved in oxidation and reduction
Molybdenum	Mo	MoO42+	Required for nitrogen fixation and nitrate reduction
Manganese	Mn	Mn2+	Activator of some enzymes, required for integrity of chloroplast membrane and for oxygen release in photosynthesis
Chlorine	Cl	Cl-	Involved in osmosis and ionic balance, probably essential in photosynthetic reactions that produce oxygen
Zinc	Zn	Zn2+	Activator or component of many enzymes
Nickel	Ni	Ni2+	Essential part of enzyme functioning in nitrogen metabolism