Question

Histogen theory was proposed by
A. Nageli
B. Schmidt
C. Hanstein
D. Wolf

Answer 1

Hint: A plant body is categorized into two parts: The underground or root part and the above ground is aerial or shoot part of the plant. The tissues that undergo divisions repeatedly and result in dimensions. i.e. length, width etc. are called meristematic tissues.

Complete Answer:
- The nageli studied cell division and pollination but became known as the man who discouraged Gregor Mendel from further work on genetics, where Schmidt proposed his hypotheses of the origin of the solar system. His theory was that at some point the sun passed through cloud dust gas.
- The histogen theory was proposed by Hanstein. The histogen theory proposes that the three principal tissues of root. i.e. vascular cylinder, cortex and epidermis originate from different groups of initial; cells or histogens in apical meristem-plerome, problem and dermatogen respectively.
(1) Dermatogen (outer layer): Give rise to epidermis of stems.
(2) Periblemt (middle layer): Give rise to cortex and endodermis.
(3) Plerome (Inner layer): Give rise to pricycle, pith and vascular tissue.
- Meristematic cells undergo repeated divisions to elongate and increase in size. Apical meristems are present in tips of root and shoot increase the width of plant vascular tissues are the special type of conducting tissues that help in transportation of food, water and minerals.

Note: The information on different kinds of tissues along with their location is important. It helps us understand the structure of the human body which in turn is helpful in various fields of research.