The macronutrients are: carbon, hydrogen, oxygen, nitrogen, phosphorus, sulphur, potassium, calcium and magnesium.

Functions of carbon, hydrogen and oxygen :

These are the components of protoplasm and all organic componds found in plants.

Functions of nitrogen.

It plays a major constituent of proteins, nucleic acids, vitamins and hormones. 

Functions of phosphorous.

Phosphate plays a key role in energy metabolism. Incorporated into ATP it is part and parcel of the universal energy currency of all types of living systems.

Fuctions of sulphur.

Sulphur is present in amino-acids - cysteine and methionine.