Question

Polyarch and exarch condition is found in
A)Monocot stem
B)Monocot root
C)Dicot stem
D)Dicot root

Answer 1

Hint:Polyarch is a condition when the number of Xylem arms/patches is more than 4. Polyarch is usually seen in Monocots. Xylem arms appear alternately with the bundles of Phloem. Exarch is a condition in which there is more than one strand of primary xylem in a root or stem. In this condition, the development of xylem starts from the periphery towards the center, i.e., centripetally.

Complete step by step answer:Option A- Monocot stem
In the monocot stem, vascular bundles are randomly placed in parenchymatous ground tissue. Pith is absent. Phloem consists of sieve tubes and companion cells. Protoxylem lacuna is present.
Option B- Monocot root
In monocot roots, vascular bundles are arranged radially. The number of Xylem and Phloem each is 8. Therefore, this condition is called Polyarch. Xylem is described as an exarch. There is no vascular cambium. Monocots have fibrous roots.
Option C- Dicot stem
In the dicot stem, the number of vascular bundles is 8 that is arranged in a broken ring-like fashion. Vascular bundles are conjoint, collateral, and open. Xylem is present on the inner surface and phloem on the outer surface. Xylem is an endarch.
Option D- Dicot root
In dicot root, vascular bundles are radial and tetrarch. Xylem Is exarch. Dicots have a tap root system. Xylem is present at the center of the root and phloem is present outside the xylem.
Thus, the correct option is Option B- Monocot root.

Note:Monocotyledons are the flowering plants (Angiosperms) in which the seeds contain only one embryonic leaf or cotyledon. Monocot leaves are characterized by the presence of parallel venation. Dicotyledons are the plants in which the seeds contain two cotyledons. These are characterized by the presence of reticulate venation.