Question

Two cross-sections of stem and root appear similar, when viewed by naked eye. But under microscope, they can be differentiated by:
A)Exarch condition of root and stem
B)Endarch condition of stem and root
C)Endarch condition of root and Exarch condition of stem.
D)Endarch condition of stem and Exarch condition of root.

Answer 1

The stem is located above the ground whereas the roots lie underneath the ground. The stem and roots do not contain vascular bundles called the xylem and phloem which help in conduction of water and minerals and transport of prepared food to various parts of the plant.

Complete answer:
To solve this question, we must know about the exarch and endarch arrangement in plants.
In the cross-sectional view, the arrangement of the vascular bundles helps in differentiating the stem from root. The exarch and endarch condition in plants is based on the arrangement of the xylem.

The endarch is the characteristics of the flowering stem. In this the protoxylem is present towards the centre and the metaxylem is present towards the periphery. The xylem develops in a centrifugal pattern. (Option B is incorrect as endarch is not the characteristic feature of root)

The exarch is the arrangement in which the protoxylem is located towards the periphery and the metaxylem is located towards the centre. This centripetal arrangement for the formation of xylem is present in the roots. (Option A is incorrect as exarch is not the characteristic feature of stem)
Option C is incorrect as endarch is not the feature of root and exarch is not the feature of stem.

Hence, the correct answer is option (D)

Note: The other two types of xylem arrangement are:
1)Centrarch- This formation is not seen in any living plants. In this the xylem forms a single chamber in the middle where the metaxylem surrounds the protoxylem.
2)Mesarch- This type of arrangement is seen in the leaves and stem of ferns. In this the xylem forms multiple strands. The strands develop from the middle to the centre of the stem and in the opposite direction towards the periphery.