Question

A nail is driven into the trunk of a 30 years old tree at a point one meter above the soil level. The tree grows in height at the rate of 0.5 meters a year. After three year the nail will be
A. 1 meter above the soil
B. 1.5 meter above the soil
C. 2 meter above the soil
D. 2.5 meter above the soil

Answer 1

Plants have cells as the basic unit, cells are organised as tissues and in turn the tissues are organised into organs. Different organs in the plant show differences in their internal structure. Within angiosperms, the monocots and the dicots are also seen to be anatomically different. Internal structures also show adaptations to diverse environments.

Complete answer:
Growth is one of the most important events in any living organism as it relates to the development and reproduction of the organism. Plants growth by producing tissues and structures such as leaves, flowers, roots etc. The growth of these parts of the plants takes place throughout life and it takes place through the meristems.
In plants, meristems are the sites of growth and are present at the tip of organs And also between the mature tissues. The growth of the shoot region is known as the primary growth and it leads to the elongation of the shoot. The increase in the width of the roots or shoots results from the widening division of the cells and known as secondary growth. Root and shoot apical meristems sometimes along with intercalary meristem, contributed to the elongation growth of plant axes. Following the cell division in root and shoot apical meristem cells, the growth could be arithmetic or geometric in nature.
The trunk is the stem which is the main axis of the tree. In plants, the development of the trunk takes place due to the formation of secondary growth. As the secondary growth takes place, it causes an increase in the width of the tree trunk.
In the above condition, when a nail is inserted into the tree trunk at a height of 1metre from the ground level, it is inserted into the area of secondary growth. The increase in length of the tree does not affect the position of the nail. It will be at the same height as its nailed tree grows from the shoot site and the elongation of the stem is related to apical growth or primary growth.

Hence, the correct answer is option (A).

Note: The growth process in plants occurs by both the elongation and increase in secondary growth which increases the width of the tree. The apical meristem allows elongation of tree trunk. So, when a nail is driven inside the tree trunk of a 30 years old tree, the nail will be at the same height which is one metre above the soil. The growth of the trunk in length will not have any effect on the height of the nail.