Extra-stelar secondary growth: The secondary growth that takes place as an alternative measure to protect the dermis and other tissues present beneath the epidermis from splitting due to the centrifugal pressure exerted for the same of intra-solar secondary growth is said to be extra-stelar secondary growth.
i) The secondary vascular tissues formed in the plant body due to intra-stelar secondary growth create centrifugal pressure.
ii) The rate of pressure is also increased, consequently with the progress of secondary growth
iii) Due to this pressure epidermis may be broken down.
iv) Moreover, an influence of this pressure may fall on hypodermis and cortex.
v) So, to protect the plant from the harmful effect caused by the intra-stelar secondary growth, secondary growth also takes place in the extra-stelar region.