Question

Differentiate between primary meristem and secondary meristem

Answer 1

The major difference between primary and secondary meristem is their origin. Primary meristems are derived from promeristem, and are responsible for primary growth. Example: Protoderm.
On the other hand, secondary meristems originate from primary tissues and are involved in secondary growth.
Example: Vascular cambium and cork cambium

Complete answer: The term meristem was given by C. Nageli (1858). Growth in plants is largely restricted to specialised regions of active cell division called meristems. Meristem shows totipotency. Meristematic tissue is self-perpetuating. On the basis of their origin meristems are of two types-primary & secondary meristems. They differentiate according to the following:

Primary meristems	Secondary meristems
It involved in the primary growth and thus it gives rise to the primary tissues of the plant	It involved in the secondary growth and thus it gives rise to the secondary tissues of the plant
It is responsible for a growth in length.	It responsible for growth in term of thickness
Cells are isodiametric i.e. having equal diameters	These cells are elongated barrel shaped or rectangular shaped
It arises from embryonic cells i.e. promeristem	It arises from permanent tissue
Vacuoles are absent in this type	Large no. of vacuoles is present
It is present in apical region of plant	It is present in lateral region of plant
Example: protoderm, procambium, etc	Example: vascular cambium and cork cambium

Note: Following divisions of cells in both primary as well as secondary meristems, the newly formed cells become structurally and functionally specialized and lose the ability to divide. They are now called permanent tissues.