Question

Who proposed the tunica corpus-theory?
(a) Hanstein
(b) Nageli
(c) Hofmeister
(d) Schmidt

Answer 1

Hint: In 1924, a theory was postulated based on the studies done on apices of shoots in angiosperms. It is called the ‘tunica- corpus theory’. It considers the different planes of cell division at the apex.

Complete answer:
Tunica corpus-theory was proposed by Schmidt. He distinguished two different zones in the shoot apex and named them as ‘tunica’ and ‘corpus’. Shoot apex in the majority of angiosperms presented with tunica which consists of two layers of cells and corpus. Researchers have designated these layers as L1, L2, and L3 denoting the outer layer of tunica, the inner layer of tunica, and corpus respectively. Plasmodesmata are located between the cells of tunica and Corpus. Plasmodesmata is believed to control the gene expression that results in the formation of protoderm, ground meristem, and provascular tissue.
Other important theories of shoot apical meristem are:
- Apical cell theory: According to this theory a single apical cell (often called apical initial) constitutes the apical Meristem. It is considered the structural and functional unit of the apical meristem.
- Histogen theory: This theory says that the tissues of a plant body originate from a mass of meristem where three histogens can be distinguished; Dermatogen, periblem, and plerome
- Tunica corpus theory differs from apical cell theory and histogen theory in its application. It applies only to the shoot apex and not to that of the root.
So, the correct answer to this question is, “Schmidt”.

Note:
- ‘Plasmodesmata’ (singular: plasmodesma) are microscopic channels that traverse the cell walls of plants and some algal cells. They, therefore, are responsible for enabling transport and communication between cells.
- Apical cell theory was advocated by Nageli in 1944.
- Histogen theory was put forward by Hanstein in 1868.