Question

Secondary xylem and phloem in dicot stem are produced by

• A. Axillary meristems
• B. Apical meristems
• C. Phellogen
• D. Vascular cambium

Answer 1

The Correct Option is D

The question asks about the origin of secondary xylem and phloem in the dicot stem. Let's explore the relevant botanical concepts to identify the correct answer.

In dicot stems, secondary growth occurs due to the activity of the vascular cambium, a type of lateral meristem. The primary function of the vascular cambium is to produce secondary xylem (toward the inside of the stem) and secondary phloem (toward the outside of the stem). This process is essential for increasing the girth of the plant, allowing it to support more weight and transport nutrients and water more efficiently.

Let's examine each option to determine its relevance:

1. Axillary meristems: These are responsible for the growth of lateral branches and are not involved in the production of secondary xylem and phloem.
2. Apical meristems: These are involved in the growth of the plant in length (primary growth) and not in the secondary thickening of the stem.
3. Phellogen: Also known as cork cambium, phellogen is responsible for producing the periderm (bark), not secondary vascular tissues.
4. Vascular cambium: This is the correct answer as it is responsible for producing secondary xylem and phloem in dicot stems.

Therefore, the correct answer is Vascular cambium.