Question

Cambium ring consists of
A. Interfascicular cambium
B. Intrafascicular cambium
C. Both A and B
D. Phelloderm

Answer 1

Hint: In dicotyledonous stems, during intra stelar secondary growth, intra-fascicular cambium (primary meristem) and interfascicular cambium (secondary meristem) join together and form into a ring of cambium is called vascular cambium.

Complete answer:
Cambium is a layer of actively dividing cells found between the xylem (forms wood) and the phloem ( forms bast) tissues. It is also responsible for the secondary growth of stems and roots (secondary growth results in an increase in thickness). The cambium present between the xylem and the phloem in the vascular bundles is known as fascicular or intra-fascicular cambium. Besides this, some cells of medullary rays (i.e., between vascular bundles) also become meristematic and form interfascicular cambium. Both of these cambia collectively make a complete ring of vascular cambium or intra-stellar cambium. This ring of vascular cambium starts cutting off cells both on the outer side and inner side. The cells that cut off on the outer side are secondary phloem and on the inner side are secondary xylem. The cambium is usually less active on the outer side than on the inner side.
Among the given options above:
Phelloderm is defined as the secondary cortex, produced by the phellogen (or cork cambium) towards the inner side.

Hence, the correct answer is option (C).

Note: The secondary growth of plants increases the thickness of the stem and it is because of the activity of the lateral meristems. There are two types of lateral tissues mainly involved in secondary growth, vascular cambium and cork cambium.