Question

Secondary xylem and phloem in dicot stem are produced by

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

Answer 1

The Correct Option is C

The question asks about the production of secondary xylem and phloem in a dicot stem. The correct answer to this is "Vascular cambium." Let's explore this concept and understand why this is the correct choice by examining the role of various meristems in plant growth:

1. Apical Meristems: These are located at the tips of roots and shoots and are responsible for the primary growth of plants, leading to an increase in length. They do not contribute to the production of secondary xylem and phloem.
2. Phellogen (Cork Cambium): This meristem is involved in the formation of the periderm, a type of secondary tissue that replaces the epidermis in plants, specifically in the formation of cork tissue. It is not involved in producing xylem and phloem.
3. Vascular Cambium: This is a lateral meristem responsible for secondary growth in plants. It leads to an increase in the thickness of stems and roots through the production of secondary xylem and phloem. The vascular cambium forms xylem on the inside and phloem on the outside of its layer, expanding the diameter of the plant.
4. Axillary Meristems: These are found in the axils of leaves and are responsible for the growth of lateral shoots. They play a role in branching but do not contribute to the production of secondary xylem and phloem.

The reasoning clearly shows that only the vascular cambium produces secondary xylem and phloem, making it the correct answer to the question.