Question

Formation of which tissue is an example of dedifferentiation:
a) Interfascicular cambium
b) Apical meristem
c) Intrafascicular cambium
d) Intercalary meristem

Answer 1

Hint: When meristematic tissue divides and ‘differentiate’ into primary permanent tissue and gets specialized to perform a particular function, that is, it loses its capacity to divide further. ‘Dedifferentiation’ is the ability of the cells to regain its capacity of cell division under certain circumstances such as during healing of a plant tissue or formation of cambium during secondary growth of plants.

Complete answer:
a) Interfascicular Cambium: It is formed during the secondary growth (increase in girth of plant). Formation of interfascicular cambium occurs from fully differentiated parenchymatous cells. It is found in adjacent vascular tissues.
b) Apical meristem: It is present at the root, shoots apex and is always a meristematic tissue and not dedifferentiated and is responsible for primary growth.
c) Intrafascicular meristem: This is a primary lateral meristem, present in between xylem and phloem.
d) Intercalary meristem: This helps in the growth of side branches-leaves, axillary buds. This is surrounded by permanent or mature tissue. Grasses grow mainly through this meristem.

Hence the correct answer is option (a).

Note:
In dicot stem, the cells of cambium present between primary xylem and primary phloem form the Intrafascicular cambium. The cells of medullary rays, adjoining these Intrafascicular cambium become meristematic (dedifferentiation) and form the interfascicular cambium, thus a continuous ring is formed. This cambial ring is responsible for the formation of secondary xylem (towards inside) and secondary phloem (towards outside).
Another ex. of dedifferentiated tissue is the cork cambium or phellogen, that develops in the cortex region while secondary growth forms cork or phellem on outer side and secondary cortex or phelloderm towards the inner side.