In the primary tissues of the stem,the cambium separating xylem and phloem is called

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

Which of the following decays rapidly when exposed to air?

In old trees,the greater part of secondary xylem is dark brown due to the

In a stratified cambium,the fusiform initials are

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: