Question

Which of the following is not a lateral meristem?
A. Intercalary meristem
B. Intrafascicular cambium
C. Interfascicular cambium
D. Phellogen

Answer 1

Meristems are specialised regions of unlimited growth; they show active cell divisions in their cells. They are divided according to the regions that they are present at like at the tips, sides or in between the plant tissues.

Complete answer:
The word meristems was coined by Carl Wilhelm Von Nageli in 1858. This word is derived from a Greek word called merizein which means to divide. Meristems are parts of the plants which consist of undifferentiated cells which are capable of cell division. Three types of meristems are found in the plants:
-Apical meristem – These meristems are present on the tips of roots (root apical meristem) and shoots (shoot apical meristem) of the plants.
-Intercalary meristem – These meristems are present in the middle of the plant's tissues. These meristems are found only in the stems of monocots
-Lateral meristems - These meristems are present on the sides of the plants and in the mature regions of roots and shoots of the plant mainly those regions which produce woody axis. These meristems include cork cambium (form the periderm of the plant), interfascicular cambium and fascicular vascular (form the vascular bundles xylem and phloem) cambium. All of these produce secondary tissues.

Apical meristem help to increase the length of roots and shoot whereas lateral meristems help in increasing the diameter of the stem. Interfascicular and intrafascicular are a part of fascicular vascular cambium that are present in between the vascular bundles and provide them support. Phellogen on the other hand is a part of cork cambium which is a lateral meristem and is responsible for the development of the periderm.

Hence, the correct answer is option (A).

Additional information:
-The cells present in the meristem can form any cell or tissue of the plants by cell division.
-Apical and intercalary meristems come under primary meristems and lateral meristem is a secondary meristem.
-After division the cells of primary and secondary meristems mature and lose their ability to divide thus forming permanent cells.
-Specialised regions of apical meristem play an important role in forming the primary body of the plant by forming vascular, ground and dermal tissues.

Note: Lateral meristem leads to secondary growth in the plants which develop thick cork cambium in the cells of roots and shoots to protect their surface from any physical injury and excessive loss of water. Cork cambium leads to the formation of cork which is a dead tissue.