In which of the following secondary growth takes place

The heartwood cannot conduct water because of

$A$. Heart wood is durable, dark and central in position.
$B$. Tyloses are balloon like structures of xylem parenchyma in vessel lumen.
$C$. Late wood is formed during spring season.

The pores present in the wall of plant's stem is called…

Lenticles are formed due to rupture in epidermis because of pressure exerted by