Question

The polyarch (xylem) is found in case of
(a) Monocot leaf
(b) Dicot root
(c) Monocot root
(d) Dicot leaf

Answer 1

Hint: The vascular bundles are arranged in a circular pattern, xylem and phloem tissue bundles are arranged in a circular fashion around the central pith, which consists of ground tissue (parenchyma). They have a larger number of vascular structures than dicot roots.

Complete step by step answer:
The arrangement during which the protoxylem lies outside and metaxylem lies inside is named exarch.
On the idea of the number of protoxylem groups, roots are often divided into monarch, diarch, triarch, tetrarch or polyarch.
In monocot roots, exarch is found within the polyarch condition i.e many protoxylem (12-20) alternating with phloem.
So, the correct answer is, ‘Monocot root.’

Additional Information:
Based on the arrangement of protoxylem and metaxylem, xylem is of two types:
- Endarch xylem
- Exarch xylem

Exarch xylem	Endarch xylem
It is the arrangement in which the protoxylem is directed towards the center and metaxylem elements towards the periphery.	It is the arrangement in which the protoxylem is directed towards the periphery and metaxylem towards the center.
The development of the xylem in this arrangement follows the centrifugal pattern.	The development of the xylem in this arrangement follows the centripetal pattern.
It is the characteristic of the stem of the flowering plants.	It is the characteristic feature of the roots.
It is a condition when there is more than one strand of primary xylem in a stem or root.	It is a condition when there is one strand of primary xylem in a stem or root.
The xylem develops from the outside inwards towards the center.	The xylem develops from the inside outwards towards the periphery.

Note: The main difference between protoxylem and metaxylem is that protoxylem is the first formed part of the xylem whereas metaxylem forms the later part of the xylem. They are both the two types of primary xylem tissues that occur during xylem.