In a dicot stem,the interfascicular cambium strip arises

As secondary growth proceeds in a tree,the thickness of which of the following increases?

The $Heartwood$ is different from $Sapwood$ due to the presence of:

In dicots and gymnosperms,secondary growth is caused by:

During secondary growth of plants,stem phellogen cuts off cells on both sides. The outer cells get differentiated into ...$A$... and the inner cells get differentiated into ...$B$... cortex.
Choose the correct combination of $A$ and $B$ with reference to the above statement.

Cork is obtained from: