The mineral elements are required by higher plants.
General functions of mineral elements are given below:
(i) 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.
(ii) 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 absorption and maintenance of cell's turgidity.
(iii) 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.
(iv) Toxic effects: Many minerals elements in their ionic form produce a toxic effect on the protoplasm Important among them are arsenic, copper, mercury etc.
(v) Catalytic effects: Several mineral elements participate in catalytic systems of plants. For example, calcium, magnesium, manganese, sodium, potassium and chlorine serve as cofactors at enzymes.
