Knots in wood are formed due to ...........

The $phellogen$ (cork cambium) develops from $...................$.

Assertion: In the stem,the pericycle takes an active part in secondary growth.
Reason: In dicots,the pericycle has the capacity to produce lateral roots.

The heartwood cannot conduct water because of

Coastal trees do not show annual rings because:

The age of a tree can be estimated by counting the . . . . . . .