The following ten points will highlight the ten important functions of mineral elements in plants.
The ten important functions are: (1) In the Formation of Plant Body (2) Osmotic Potential of Cells (3) Acidity and Buffer Action (4) Influence on Permeability of Cytoplasmic Membranes (5) Catalytic Effects (6) Toxic Effects (7) Balancing Effects (8) Antagonistic Effects (9) Maintenance of Electrostatic Neutrality and (10) Phloem Transport.
Mineral elements perform many vital functions in plants, and some of these are given below briefly:
Function # 1. In the Formation of Plant Body:
Various mineral elements are constituents of the organic molecules found in the protoplasm and cell wall of the plants. For instance, the well known non-mineral elements, such as carbon, hydrogen and oxygen are the components of the carbohydrates which constitute the major part of the cell wall and protoplasm.
Similarly, nitrogen and sulphur are found in proteins, phosphorus in nucleoproteins and nucleic acids, and calcium in calcium pectate of the cell wall. Magnesium is an important constituent of chlorophyll and iron is found in cytochromes.
Function # 2. Osmotic Potential of Cells:
The osmotic potential of the plant cells depends on the concentration of mineral salts and organic compounds found in the cell sap. Suitable osmotic potential is required for water absorption and maintenance of cell turgidity.
Function # 3. Acidity and Buffer Action:
The mineral elements, absorbed from the soil by the roots, affect the H+ ions concentration and thus influence the pH of cell sap. They also constitute major buffer system of the plants. For example, sodium (Na+) and some other monovalent increase membrane permeability while calcium (Ca++) and other divalent decrease the same.
Function # 4. Influence on Permeability of Cytoplasmic Membranes:
The permeability of cytoplasmic membranes is influenced by the presence of various cations and anions of the mineral elements. Some ions are observed to increase the permeability while others decrease it. For example, sodium and some other monovalent increase membrane permeability while calcium and other divalent decrease the same.
Function # 5. Catalytic Effects:
Several mineral elements like copper, iron, zinc, manganese, magnesium and cobalt etc., participate in catalytic systems of plants.
Function # 6. Toxic Effects:
Many mineral elements in their ionic form when present in concentrations higher than the normal, produce a marked toxic effect upon the protoplasm. Important among such minerals are arsenic, mercury and copper etc.
Function # 7. Balancing Effects:
Calcium, potassium and magnesium are known for their balancing property, i.e., they neutralize the toxic effect of other minerals by retaining the ionic balance.
Function # 8. Antagonistic Effects:
The phenomenon of interaction in which the normal effect of one ion is counteracted or negated by that of another ion is called antagonism or antagonistic effect. Such antagonistic effects are seen in mineral solutions. For example, manganese in concentration of 300 to 400 ppm on dry weight basis in barley is toxic when the nutrient solution does not contain silicon, but is harmless when silicon is present.
Function # 9. Maintenance of Electrostatic Neutrality:
Mineral elements also help the cells in maintaining electrostatic neutrality (i.e., (+) ve and (-) ve charges, cations and anions balancing each other). For example, Na+, K+, Ca++, Mg++ found in the cells balance the anions of organic and Inorganic acids.
Function # 10. Phloem Transport:
Boron and potassium are involved in the translocation of organic substances in the phloem.