Question

Tunica corpus theory was proposed by
(a)Schmidt
(b)Strasburger
(c)Nageli
(d)Hofmeister

Answer 1

Hint: Tunica corpus theory of shoot apical meristem is observed in the angiosperm only. Cryptograms and a larger number of gymnosperms do not show tunica corpus arrangement.

Complete answer:
The Tunica corpus theory was proposed by ‘Schmidt’ in 1924. This theory is relevant only to shoot apex. It is based on the plane of division of cells. According to this theory, the shoot apex consists of two distinct layers, namely, Tunica and Corpus. The shoot apex is composed of two layers of cells of tunica and corpus.
-Tunica: It is single-layered and creates epidermis. The cells of tunica are smaller as compared to corpus and divided by anticlinal divisions mostly.
-Corpus: It represents the central core with larger cells. The cells divide into all planes (anticlinal and periclinal).
Additional information:
Tunica forms a protoderm which gives rise to the sterna and leaves the epidermis. Corpus is the inner mass that splits to create procambium and terrestrial meristem. Sometimes, tunica is multilayered, and then only the outer layer builds the epidermis and the leftover layers with a corpus from the cortex of the shoot.
The plasmodesmata link remains between the cells of tunica and corpus. It is of the view that plasmodesmata command the gene expression that leads to the development of protoderm, ground meristem, and provascular tissue.
Merits of Tunica Corpus theory:
-It deals with one thing i.e. planes of cell division. As a result, the explanation of the meristem becomes correct.
-It has topographical value in the studies of the development of different tissue systems in plants.
-The destiny of the derivatives of the corpus is not predetermined.
-The derivatives of the zones are not rigid like histogen theory.

So, the correct answer is ‘Schmidt’.

Note: Tunica is characterized in having an anticlinal plane of cell divisions, i.e., the division wall is laid down perpendicular to the surface. This division reflects the surface growth in the apex. Corpus shows both the divisions. Periclinal divisions are the ones that take place parallel to a tissue or surface of an organ.