The age of a tree can be estimated by counting the . . . . . . .

$I.$ 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.

Seasonal activity of vascular cambium is influenced by many factors,except

Trunks of some of the aged tree species appear to be composed of several fused trunks. Is it a physiological or anatomical abnormality? Explain in detail.

Increase in the girth of plant (organ) takes place by

Describe the contribution of cork cambium in secondary growth.