Macronutrients: Elements which are present in large amounts in plant tissues are called macronutrients. They are in excess of 10 mmole per kg of dry matter. Carbon, hydrogen, oxygen, nitrogen, phosphorous, sulphur, potassium, calcium and magnesium are the macronutrients.
Micronutrients: Elements which are present in small amounts, i.e. less than 10 mmole per kg of dry matter are called micronutrients. Iron, manganese, copper, molybdenum, zinc, copper, boron, chlorine and nickel are the micronutrients.
Beneficial Elements: Apart from the 17 essential elements, many other elements are required by plants. For example; sodium, silicon, cobalt and selenium are required by higher plants.
Toxic Elements: If a mineral ion concentration in tissues reaches to a level that it reduces the dry weight of tissues by about 10%, the mineral then becomes toxic. This shows that any element can become toxic if it crosses a certain threshold in plants.
