The activity of cambium in plants is under the control of
Many physiological factors
Many environmental factors
Only water availability
Both ($a$) and ($b$)
In a stem which is covered by periderm and in which stomata are absent, gaseous exchange takes place through
$I.$ Annual rigs are formed as a result of seasonal environmental conditions
$II.$ Tracheids/vessels elements are larger during periods when water is abundant
$III.$ Tracheids/vessels elements have thicker wall during periods of water deprivation
$IV.$ Wood formed in the previous years is darker than newer wood
Select the combination of correct statements from the options given below
Which tissue gives rise to secondary growth?
Initiation of lateral roots and vascular cambium during secondary growth takes place in cells of :