Question

The youngest layer of secondary phloem in woody dicot stem is located____________

• A. Just outside the vascular cambium
• B. Just on the inner side of cambium
• C. Between periderm and primary cortex
• D. Just outside pith

Answer 1

The correct option is A Just outside the vascular cambium

• The cambial ring exhibits mitotic activity on both sides. The mitotic activity on the inner surface results in the formation of cells, which differentiate into a set of xylem.
• It represents the secondary xylem. Similarly, the mitotic activity on the outer surface results in the formation of cells, which differentiate into a set of phloem. It represents the secondary phloem.
• Due to the formation of secondary xylem, the primary xylem becomes pushed more towards the pith and the pith gets slightly reduced. However, the secondary phloem grows and completely masks the primary phloem. Hence, it is not visible.

Therefore, the correct answer is option A