Question

You are given a fairly old piece of dicot stem and a dicot root. Which of the following anatomical structures will you use to distinguish between the two?

• A. Secondary phloem
• B. Cortical cells
• C. Protoxylem
• D. Secondary xylem

Answer 1

The correct option is C

Protoxylem

The correct option is C.

Explanation of the correct option:

1. It is the primary xylem that develops during the primary growth of a plant.
2. One can distinguish between a stem and a root of a dicot plant by observing the position of the protoxylem.
3. In stems, the protoxylem is located towards the centre (pith) and the metaxylem is located towards the periphery of the organ.
4. This type of primary xylem is called endarch.
5. Whereas in roots, the protoxylem is located towards the periphery and the metaxylem is situated towards the centre.
6. This type of xylem is called exarch.

Explanation of the incorrect options:

Option A:

Secondary phloem is a type of phloem formed from the vascular cambium during secondary growth.

Option B:

Cortical cells are the cells that form a layer of cells forming cork.

Option D:

Secondary xylem is a type of phloem formed on the inner edge of cambium ring during secondary growth.

Final answer: If we are given a fairly old piece of dicot stem and a dicot root, protoxylem will be the anatomical structure to distinguish between the two.