What is meant by secondary growth? Which meristems are responsible for the secondary growth ?

Explanation

Secondary growth. The formation of secondary tissues from the lateral meristem is called secondary growth. It increases the diameter of stem. Secondary tissue is formed from two types of lateral meristems.
Meristems responible for secondary growth
1. Vascular cambium is present between primary xylem and primary and this is called the fascicular cambium. In the medullary region interfascicular cambium is formed between two vascular bundles. Interfascicular and fascicular cambia form the complete ring in the stem. Cambium cells divide to form secondary xylem and secondary phloem.
2. Cork cambium or phellogen. Cork cambium or phellogen develops in the cortex. This cork cambium prodcues the cork ( phellem) tissue towards the epidermis and produces the phelloderm on the inner side. Cork cambium ( phellogen), cork ( phellem) and phelloderm constitute the periderm which is protective in nature.