Estimation of the age of the tree is done by

Diffused porous woods are characteristic of plants growing in

Which of the following pairs is suitable for the detailed study of secondary growth in plants?

Identify $X$ and $Y$ in the given diagram of secondary growth in a dicot stem.

What is/are true about heartwood?
$I.$ It does not help in water conduction.
$II.$ It is also called alburnum.
$III.$ It is dark in colour but very soft.
$IV.$ It has tracheary elements,which are filled with tannin,resin,etc.

Read the components $a$ to $d$ given in the note and identify the correct sequence of components from the outside to the inside of a mature stem:
$(a)$ Secondary cortex
$(b)$ Wood (Secondary xylem)
$(c)$ Secondary phloem
$(d)$ Phellem (Cork)