Theories of Shoot Apex MCQ - Practice Questions with Answers

Shoot Apex and the Theories related to Shoot Apex

• The shoot apex is derived from the meristem present in the plumule of the embryo.
• It is present at the tip of the stem.
• The axillary bud represents the left behind cells of the shoot apical meristem. It is present in the axil of the leaves.
• The shoot apex is dome-shaped and the base of the meristem divides to form flanks of leaf primordia.

Theories Related to Shoot Apex

1. Apical Cell Theory: It was given by Nageli in 1858. It provides for a single apical meristematic cell at the shoot tip. This theory holds true for higher algae, bryophytes, and pteridophytes.

2. Histogen Theory: It was given by Hanstein in 1870. It provides for layers of meristematic cells giving rise to specific sets of tissues as follows:
a) Dermatogen: it forms the epidermal tissue system.
b) Periblem: it forms the cortex.
c) Plerome: it forms the vascular tissues.

3. Tunica Corpus Theory: It was given by Schmidt in 1924. It provides for two distinct zones in the shoot apex:
a) Tunica: It gives rise to the epidermis. It divides into anticlinal divisions.
b) Corpus: It is the central core and divides to give volume to the plant body. 
 

Types of Shoot Apex:

1. Monoplex Type: In this type of shoot apex, there is only a single apical cell that represents the shoot apical meristem. It is seen in higher algae, bryophytes, and pteridophytes.

2. Simplex Type: In this type of shoot apex, there is a single layer of meristematic cells that represent the shoot apical meristem. It is seen in gymnosperms.

3. Duplex Type: In this type of shoot apex, there are multiple layers of meristematic cells that represent the shoot apical meristem. It is seen in angiosperms.