Question

A common character of monocot and dicot roots is-
a. Exarch protoxylem
b. Endarch xylem
c. Number of xylem strands
d. Occurrence of secondary growth

Answer 1

Hint: A condition of primary growth of xylem in which the protoxylem appears towards the periphery and towards the middle the metaxylem occurs. The growth of the xylem follows the centripetal pattern in this arrangement.

Complete answer:
> Option A is correct. The morphology of the dicot root and the monocot root in most characters is more or less similar. They are epidermis, cortex general, endodermis, vascular bundle type, xylem nature. Some typical characteristics include the presence of exarch xylem, the presence of Casparian band single-layered endodermis, the presence of parenchymatous general cortex, etc.

> Option B is incorrect. There are eight Dicot stem vascular bundles, arranged in the shape of a broken ring. Conjoint, collateral and open are the vascular bundles. There's Xylem on the inner surface, and there's phloem on the outside surface. Xylem is classified as Endarch.

> Option C is incorrect. Vascular bundles in the monocot root are radial in arrangement. Eight bundles of xylem and phloem are in each one. The condition, therefore, is defined as polyarch. Xylem is known in the monocot root as an exarch.

> Option D is incorrect. Secondary growth happens in dicot plants, but secondary growth is typically lacking in monocots. Cambium is the layer of continuously dividing cells that is responsible for the secondary growth of stems and roots between the xylem and phloem tissues. New layers of phloem on the outside of xylem on the inside are formed by the cambium, thus growing the stem diameter. While development is primary, growth occurs at the tips of stems and roots as a result of cell division, causing them to elongate and giving rise to primary tissue.

Hence, the correct answer is option (A).

Note: Protoxylem, consisting of narrow, thin-walled cells, is the first component of the primary xylem that matures first, and these cells are typically smaller than metaxylem. Exarch growth is generally known to be the roots of vascular plants.