In which of the vascular bundles xylem is surrounded by phloem

Options

A. Collateral
B. Leptocentric
C. Hadrocentric
D. Radial

Answer

To answer the question "In which of the vascular bundles is xylem surrounded by phloem?", we need to analyze the different types of vascular bundles mentioned in the options: collateral, leptocentric, hydrocentric, and radial.

### Step-by-Step Solution:

1. **Understanding Vascular Bundles**: Vascular bundles are arrangements of xylem and phloem in plants that facilitate the transport of water, nutrients, and food. The arrangement of xylem and phloem can vary in different types of vascular bundles.

2. **Identifying Hydrocentric Vascular Bundles**: Hydrocentric vascular bundles, also known as amphicrybral bundles, have a central strand of xylem surrounded by a ring of phloem. This means that in hydrocentric bundles, the xylem is indeed surrounded by phloem.

3. **Evaluating Other Options**:
- **Collateral Vascular Bundles**: In collateral bundles, xylem and phloem are located side by side on the same radius. This does not fit the criteria of xylem being surrounded by phloem.
- **Leptocentric Vascular Bundles**: In leptocentric bundles, phloem is surrounded by xylem on all sides, which is the opposite of what we are looking for.
- **Radial Vascular Bundles**: In radial bundles, xylem and phloem are separated from each other by non-conducting tissues, which also does not meet the requirement of xylem being surrounded by phloem.

4. **Conclusion**: After analyzing all the types of vascular bundles, we conclude that the correct answer is hydrocentric vascular bundles, where xylem is surrounded by phloem.

### Final Answer:
The correct type of vascular bundle in which xylem is surrounded by phloem is **hydrocentric**.

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