Question

How many histogens are present in monocot root apex?

• A. 1
• B. 2
• C. 3
• D. 4

Answer 1

The correct option is D 4

According to histogen theory, as proposed by Hanstein, the root and shoot apices have three distinct meristematic regions, called as histogens. These are namely dermatogens, periblem and plerome. The dermatogens makes uniseriate epidermis by anticlinal divisions, periblem forms cortex and plerome serve as progenitor of stele (pericycle, vascular bundles, pith rays or medullary rays and pith).

Casuarina is exception to this theory and has two histogens. Ranunculus is also exception to this theory and has one histogens.

Monocotyledons have four histogens, calyptrogen being the fourth one that makes root cap. Thus the correct answer is option D.