The type of arrangement of xylem and phloem on alternate radii is described as

Options

A. Radial
B. Diagonal
C. Pyramidal
D. Tangential

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the arrangement of xylem and phloem in a plant. Specifically, it refers to their positioning on alternate radii.

2. **Defining Radii**: A radius is a line segment that connects the center of a circle to its outer edge. In the context of plant anatomy, "alternate radii" means that the xylem and phloem are arranged in such a way that they alternate around the center of the vascular bundle.

3. **Visualizing the Arrangement**: To visualize this, imagine a circular cross-section of a plant. If you were to draw lines from the center to the edge (the radii), you would place xylem on one radius and phloem on the next, continuing this pattern around the circle.

4. **Identifying the Type of Arrangement**: This specific arrangement, where xylem and phloem are positioned on alternate radii, is known as the "radial arrangement" of vascular bundles.

5. **Context of the Arrangement**: This radial arrangement is commonly observed in the anatomy of dicot roots, where the vascular bundles are organized in such a manner to facilitate efficient transport of water and nutrients.

6. **Conclusion**: Therefore, the answer to the question is that the type of arrangement of xylem and phloem on alternate radii is called the "radial arrangement of vascular bundles."

---