A transverse section of the trunk of a tree shows concentric rings which are known as annual rings . How are things rings formed ? What is the significance of these rings ?

Explanation

a) The wood formed during spring season shows more number of xylem vessels having wider lumen. This is known as spring wood.
b) The wood formed during autumn season shows less number of xylem vessel having narrow lumen. This is known as autumn wood.
c) The spring wood and autumn wood that appear in a year as concentric ring in secondary organs of dicotyledons constitute annual rings.
d) By counting the number of annual rings, the approximate age of trees can be estimated.