Question

How many shoot apical meristematic zones are expected in a twig of a plant possessing 9 branches, 39 leaves?
A. 9
B.39
C. 10
D. 8

Answer 1

Hint: The word apical means apex or tips.Shoot apical meristematic zones are present at the tip of stems and branches. Number of shoot apical meristematic zones depends upon the number of branches a plant possesses.

Complete answer:
Plant tissues are of two types:- meristematic tissue and permanent tissue. Meristematic tissues are growth tissues and are present in the growing region of the plant. Cells of the meristems divide continuously and help in increasing the length and girth (thickness) of the plant. According to their position in the plants, meristematic tissues are of three types:- apical meristems, lateral meristems and intercalary meristems.
Apical meristems are located at the growing tip of stems and roots. It brings about the elongation of the root and stem. It results in an increase in the height of the plant, which is called primary growth. Based on their position, apical meristem are of two types:- Shoot apical meristem (SAM) and Root apical meristem (RAM). They consist of undifferentiated cells or meristematic cells. They are capable of cell division both SAM and RAM divide rapidly and increase the length of stems and roots.

A twig of a plant possessing 9 branches and 39 leaves is expected to have 10 shoot apical meristematic zones. As discussed above, shoot apical meristem (SAM) is a group of dividing cells, present at the tip of stem as well as the tip of each branches, so in the given question there are 9 branches in a twig of a plant hence 9 shoot apical meristematic zones are likely to be present. Besides branches, a twig (main stem) itself has 1 shoot apical meristematic zone. Hence, the total number of shoot apical meristematic zones is 10.
So, the correct answer is “Option C”.

Additional Information:
To understand well, we can take another example:- If a twig of a plant has 4 branches and 26 leaves, then how many shoot apical meristematic zones are likely to exist? The answer will be 5 shoot apical meristematic zones. This is because the total number of branches is 4 and a twig itself is a main stem. All of them have shot apical meristematic zones at their tips.

Note:
Lateral meristems are found beneath the bark and in vascular bundles of dicot roots and stems. It is mainly responsible for increasing the girth and diameter of roots and stems. This is called secondary growth.
Intercalary meristems are located at the base of leaves or internode. It increases the length of organs such as leaves and internodes.