Question

In a monocot root, vascular bundles are

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

Hint:

Remember that roots have radial vascular bundles. For monocot roots, the characteristic feature is a large number of xylem bundles (polyarch), whereas dicot roots have fewer xylem bundles (diarch to hexarch).

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks to characterize the arrangement of vascular bundles specifically in a monocot root.

Step 3: Detailed Explanation:
1. Root characteristics: In roots (both monocot and dicot), the vascular bundles are typically radial, meaning the xylem and phloem are arranged alternately on different radii. This distinguishes them from stems, where bundles are conjoint.
2. Monocot vs. Dicot roots:
* Dicot roots: Usually have fewer xylem bundles (diarch, triarch, tetrarch, or pentarch), typically 2 to 6.
* Monocot roots: Generally have more than six (often 8 or more) xylem bundles. This condition is described as polyarch. They also lack a vascular cambium, so they are 'closed' in that sense, but 'radial' and 'polyarch' are the defining characteristics of their arrangement.
3. Open/Closed: While monocot roots are 'closed' as they lack cambium and don't show secondary growth, this term is primarily used for stems. For roots, the arrangement (radial) and number of xylem bundles (polyarch) are more specific descriptors. Diarch refers to two xylem bundles.
Therefore, in a monocot root, vascular bundles are radial and polyarch.

Step 4: Final Answer:
The correct option is (C) Radial, polyarch.

Answer 2

The question is about the vascular bundle arrangement specifically in a monocot root, so each option needs to be checked against both the type of arrangement (radial vs conjoint) and the number of xylem groups (polyarch vs diarch).

1. Conjoint, collateral, open: Conjoint and collateral describe a stem, not a root. Roots never place xylem and phloem side by side on the same radius, so this option is describing the wrong organ from the start.
2. Conjoint, collateral, closed: This again applies the stem-type arrangement to a root, which is incorrect regardless of what "closed" adds to it.
3. Radial, polyarch: "Radial" correctly places the xylem and phloem on separate, alternating radii, which is how every root is built. "Polyarch" means many xylem groups - typically more than six - and this high number of xylem patches is a hallmark of monocot roots specifically, distinguishing them from dicot roots.
4. Radial, diarch: "Radial" is correct for a root, but "diarch" means only two xylem groups, which is a feature of some dicot roots, not monocot roots.

The arrangement has to be radial because it is a root, and the xylem count has to be polyarch because it is specifically a monocot root.

Therefore, the correct answer is Radial, polyarch.