What is the significance of secondary growth?

The significance of secondary growth are :
(a) The secondary growth adds girth to the plant. It . provides support to increasing weight of the aerial growth.
(b) It produces a corky bark around the tree trunk that protects the interior parts from abrasion, heat, cold and infection.
© It adds new conducting tissues for replacing old non-functioning ones as well as for meeting increased demand for long distance transport of sap and organic nutrients.