Sapwood differs from heartwood in being:

Given below are two statements: One is labelled as Assertion $A$ and the other is labelled as Reason $R$:
Assertion $A$: Late wood has fewer xylary elements with narrow vessels.
Reason $R$: Cambium is less active in winters.
In the light of the above statements,choose the correct answer from the options given below:

Physiologically,the active part of the wood is ..........

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

The increase in the thickness of the stem is due to the activity of . . . . . . .

The feature which is common to both heartwood and sapwood is