General functions of mineral elements are given below:
(a) Constituents of plant body : Various mineral elements become permanent constituents of molecules found in the protoplasm and cell wall. Elements like carbon, hydrogen and oxygen are used in the formation of carbohydrates. Nitrogen is an essential component of all amino acids, protein, nucleic acids, chlorophyll, auxins, cytokinins and vitamins. Calcium is a constituent of calcium pectate of middle lamella. Magnesium is an essential part of the chlorophyll molecule and also activates certain enzymes.
(b) Osmotic potential of cells: The osmotic potential of a cell is maintained by the inorganic salts present in the cell sap. Osmotic potential is required for water j absorption and maintenance of cell's turgidity.
(c) Acidity and buffer action : The mineral elements absorbed from the soil, affect the H+ ion concentration and thus influence pH of cell sap. They also constitute major buffer system of the plants.
(d) Permeability of cytoplasmic membranes : The
permeability of cytoplasmic membranes is affected by the presence of various cations and anions in the external medium. Monovalent cations commonly increase the membrane permeability, while divalent |cations decrease the same.
(e) Toxic effects : Many minerals elements in their ionic form produce a toxic effect on the protoplasm, Important among them are arsenic, copper, mercury etc.
(f) Catalytic effects : Several mineral elements
participate in catalytic systems of plants. For example, calcium, magnesium, manganese, sodium, potassium and chlorine serve as cofactors of enzymes. Potassium and boron are involved in the translocation of organic substances in the phloem.
(g) Antagonistic effects: Some of the mineral elements
antagonise or balance the harmful effect of certain j other elements. For example, manganese in barley plant is toxin in absence of silicon, but is harmless in presence of silicon.