a) Provide basic structure to the plants eg. carbon, hydrogen and oxygen.
b) Energy storage, transfer and bonding eg. N, S and P.
c) Necessary for charge balance eg. K, Ca, and Mg. These elements act as regulators and carriers.
d) Enzyme activation and electron transport eg. Fe, Mn, Zn, Cu, B, Mo and Cl. These are catalysers and activators.