Question

The vascular bundle in a dicot stem is

• A. Conjoint, collateral, closed
• B. Conjoint, collateral, open
• C. Radial, closed
• D. Radial, open

Hint:

Remember the key features:
- Stem (Dicot): Conjoint, collateral, open (for secondary growth).
- Stem (Monocot): Conjoint, collateral, closed (no secondary growth).
- Root (Both): Radial.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
The question asks to describe the characteristics of vascular bundles found in a dicot stem.

Step 3: Detailed Explanation:
Vascular bundles are complex tissues that contain xylem and phloem. Their arrangement and structure vary among different plant parts (stems, roots) and plant types (monocots, dicots).
1. Conjoint vs. Radial: In a dicot stem, xylem and phloem are located on the same radius, which is termed conjoint. Radial bundles (xylem and phloem on different radii) are characteristic of roots.
2. Collateral vs. Bicollateral: In a dicot stem, the phloem is located towards the periphery and xylem towards the center, with no phloem internal to the xylem. This arrangement is called collateral. Bicollateral bundles have phloem on both outer and inner sides of the xylem.
3. Open vs. Closed: Dicot stems exhibit secondary growth (increase in girth), which is facilitated by the presence of a vascular cambium. Vascular bundles with cambium are called open vascular bundles. Closed bundles lack cambium and thus cannot undergo secondary growth (typical of monocot stems).
Therefore, vascular bundles in a dicot stem are conjoint, collateral, and open.

Step 4: Final Answer:
The correct option is (B) Conjoint, collateral, open.