Question

If there is more than one tunica layer in a stem apex.
Which among the following is most likely to happen?
A. All the layers will develop into epidermal cells
B. Only the outer layer will develop into epidermis cells
C. All the layers will develop into cortex
D. Inner layer develops into cortex

Answer 1

Hint: The terminal meristem at the basis of the stem and its branches is called shoot apex. It is found either at the plumular tip of the embryo or in the axil of a leaf. The shoot apex lies immediately above the uppermost primordial leaf. It is readily symmetrical and appears like a cone with rounded apex. It varies in shape and size and different plants are in different branches of the same plant.

Complete answer:
From the tunica corpus theory of Schmidt, we know that leaf primordia protects the dome-shaped shoot effects which can be differentiated into:
-Tunica: It is an outer zone that gives rise to the epidermis or protoderm. Cell division occurs at the right angle to the surface of the effects finally giving rise to surface growth.
-Corpus: It is the lower multilayered finally gives rise to procambium and ground meristem. Procambium forms vascular tissues and ground meristem gives rise to ground tissues. Procambium gives rise to primary xylem, primary phloem and intra fascicular cambium. The ground meristem forms the ground tissue that is cortex pith, endodermis and pericycle.
The epidermis is the outermost layer of the main plant body. The epidermal cells are a long gated arrangement to form a continuous layer. This layer is interrupted by stomata. Sometimes they are separated by intercellular spaces. Epidermal system forms the outermost covering of the whole plant body.
So, it can be concluded that, if there is more than one tunica layer in a stem apex, then only the outer layer will develop into epidermis cells.

Hence, the correct answer is option (b).

Note: Some other theories have also been put forward to describe the structure and organization of shoot apex, for example, histogen theory which was proposed by Hanstein. The theory describes dermatogen, periblem and plerome as three distinct meristematic zones of shoot apical meristem.