Question

The cross-section of a trunk of a tree showed 50 annual rings. The age of tree is
A. 50 years
B. 50 months
C. 100 years
D. 25 years

Answer 1

Plants are capable to continue the process of growth throughout their entire lives. The growth in plants takes place through the combination of two types of processes such as cell growth and cell division. The process of cell division is mitosis and it increases the number of cells while cell growth increases the cell size. Secondary growth helps the tree to increase in diameter and girth.

Complete answer:
Growth rings are layers of wood formed in a tree trunk that are formed during a single year growth or single growth period. It can be described as a layer of growth of the secondary xylem that can be seen in the cross section of a woody part of the tree like stems or branches. They appear as concentric circles of different width. They are produced by tissues known as cambium. It is affected by certain changes in environmental conditions. The growth rings are reflected by a single year’s growth, so they are referred to as annual rings.
The growth season affects the pattern of growth in the trees leading to formation of growth rings.
The trees of the temperate regions or where the growth period is annual or limited, shows distinct growth rings while areas like the tropics, where growth period is longer, growth rings appear irregular and conspicuous. Often, by counting the growth rings on a tree trunk the age of the tree can be calculated.
By counting the annual growth rings, we can calculate the age of the tree. So, if the cross-section of a trunk of the tree shows about 50 annual rings, then the age of the tree will be 50 years.
As the rings are annual information at the end of 100 years, the annual rings will be equal to 100. Similarly, for 25 years, the annual rings will be 25.
So, the correct answer is “Option A”.

Additional Information:
In the temperate regions, the trees usually have a growth period of one year. The trees in these regions are very much prominent. While in tropical areas, the duration of the growth period is longer and it allows the trees to grow continuously. The trees of the tropical regions do not show clear growth rings.

Note: The growth rings in tree trunks are formed by the cambium. IT is a thin, continuous sheath of cells that is found between bark and wood. The growth rings are produced annually and one annual ring is added per year. So, if a cross-section of a trunk of a tree shows 50 annual rings, the age of the tree can be calculated as 50 years.