Question

The apical cell theory was replaced by histogen theory by?
A. Hofmeister
B. Nageli
C. Schmidt
D. Hanstein

Answer 1

Hint: Hanstein replaced the apical cell theory to histogen theory. In 1868, Hanstein divided the shoot apex into various zones. Each zone of shoot apex consisted of a group of initial cells called as histogen or a tissue builder.

Complete answer:
The major histoge the stem and roots are as follows:
(a) The dermatogen, a meristematic external layer
(b) The plerome, a central core
(c) The periblem, the region between the above two.

> Option (A) is Hofmeister
Wilhelm Friedrich Benedikt Hofmeister, a German biologist and botanist is one of the true giants in the history of biology and belonged to the same pantheon as Darwin and Mendel. He was mostly self-taught.

> Option (B) is Nageli
A Swiss botanist, Carl Wilhelm von Nägeli studied cell division and pollination but came to be known as the man who discouraged Gregor Mendel from his further work on genetics. He rejected the method of natural selection as a mechanism of evolution and favoured orthogenesis driven by a supposed “the inner perfecting principle”.

> Option (C) is Schmidt
Ernst Johannes Schmidt was a Danish biologist who was credited in 1920 for discovering that the European eels migrate to the Sargasso Sea to spawn. Prior to this, people of North America and Europe had wondered why there were no baby eels where they used to do fishing.

> Option (D) is Hanstein
Hanstein is remembered for his studies in plant anatomy and morphology. The "histogen theory" was introduced by Hanstein in 1868 which explained the shoot apex behaviour in plants. Along with his close friend, Nathanael Pringsheim (1823-1894), he also conducted pioneer research on the fertilization process in ferns.

Hence, The correct answer is option (D).

Note: In 1857, the apical cell theory was proposed by Hofmeister and was supported by Karl Wilhelm von Nageli in 1878. According to them the shoot apex of most vascular cryptogams consists of a single pyramidal cell or the single apical cell which is responsible for the formation of the shoot and successive growth of the plant. The apical cell theory was replaced by the concept that the different parts of a plant body have independent origin in case of higher plants. So the apical cell theory was later superseded by histogen theory.