The site of origin of lateral roots and the formation of cork cambium are features related to:

The youngest layer of secondary xylem is situated in .............

The activity of cambium in plants is under the control of

The cell wall is impermeable to water and the deposition of suberin is also found in:

Grafting cannot be done to monocots because they lack

$I.$ Annual rings are formed as a result of seasonal environmental conditions.
$II.$ Tracheids/vessel elements are larger during periods when water is abundant.
$III.$ Tracheids/vessel elements have thicker walls during periods of water deprivation.
$IV.$ Wood formed in previous years is always darker than newer wood.
Select the combination of correct statements from the options given below.