Question

According to histogen theory, the epidermis is formed by
A. Dermatogen
B. Protoderm
C. Periblem
D. Plerome

Answer 1

Hint: Histogen theory was given by a German botanist Hanstein in the year 1870, According to this theory the apical meristematic tissue gives rise to shoot apical meristem which is located at the tip of the shoot in plants.

Complete Answer:
- The three meristematic zones according to Histogen theory given by Hanstein are dermatogen, periblem and plerome.
- The outermost meristematic layer is dermatogen which forms the epidermal tissue as well as the epidermis.
- The middle meristematic layer which is located between the dermatogen and the plerome is called periblem and it forms the cortex and the endodermis.
- The innermost meristematic layer is called the plerome which gives rise to the stele and the pith and the plerome forms the core of the plant.

Option(A): The Dermatogen forms the epidermal tissue system and the epidermis of the plant, therefore this is the Correct option.

Option(B): The meaning of protoderm and dermatogen is the same, therefore this is also the Correct option.

Option(C): Periblem forms the Cortex and the endodermis of the plant, therefore this is an Incorrect option.

Option(D): Plerome forms the stele and pith of the plant which consists of Xylem, phloem, and the pericycle, therefore this is an Incorrect option.

Hence the correct answer is option A.

Note: - Epidermis is a layer of cells arranged in a single sheet-like manner that covers the outer part of the plant.
- Histogen theory is the same for both Angiosperms and Gymnosperms.
- Hanstein proposed Histogen theory by replacing apical cell theory given by Hofmeister which stated that shoot formation is done by single pyramid-shaped cells.