A large number of substances are required from outside for completion of a life cycle normally and efficiently. The chemical substances that provide nourishment to living organisms are called nutrients. Nutrition is the process involving the absorption of various mineral ions by the plants for their growth and development.

Under normal conditions of growth, all chlorophyll containing green plants are autotrophic i.e. they can manufacture their own food. However, they need from outside the supply of inorganic substances. Except for hydrogen, carbon and oxygen which constitute about 90 per cent of dry weight, all other inorganic plant requirements are obtained from soil. It is well known that the yield of a crop depends upon the mineral constitution of the soil. As the sources of these inorganic requirements are minerals, the elements are called mineral nutrients and thus nutrition is known as mineral nutrition. Many of them are represented as a part of structural organic compounds e.g., nitrogen, phosphorus, sulfur and calcium. Nitrogen and sulfur are taken up in the inorganic form and are converted into organic molecules as amino acids.

Still others as copper, iron, manganese and cobalt are constituents of enzymes, and act as catalytic molecules. Some enzymes require metals as cofactors. Iron is required by the plants for the formation of cytochromes. For conversion of sugars into starch,
cellulose, fats, amino acids and other complex organic molecules, many inorganic ions and molecules are needed. Similarly, green plants need water and carbon dioxide for the formation of sugar during the process of photosynthesis. Some of the elements accumulate as stored ionic substances e.g. selenium, strontium, sodium, potassium. In general sense, mineral nutrition is a broad field concerned with the complex bio-synthetic events by which higher plants produce organic materials from inorganic materials absorbed from their environment.