Question

Conjoint, collateral, closed vascular bundles present in:
I. Monocot stem
II. Dicot leaf
III. Monocot leaf
IV. Roots

• A. I, II, III
• B. I, II, III, IV
• C. I only
• D. II, III only

Hint:

Conjoint collateral closed bundles = no cambium, no secondary growth.

Answer 1

The Correct Option is A

Three terms describe a vascular bundle here: conjoint (xylem and phloem on the same radius), collateral (phloem to one side of xylem, not surrounding it), and closed (no cambium, so no secondary growth). The question asks where all three apply together.

1. Monocot stem: Vascular bundles here are scattered through the ground tissue, each one conjoint, collateral, and lacking cambium, which makes it closed. This is a textbook example.
2. Dicot leaf: Leaves, whether from monocots or dicots, do not undergo secondary growth, so their bundles never develop cambium either. A dicot leaf's bundles are conjoint, collateral, and closed, same as the monocot stem.
3. Monocot leaf: For the same reason, a monocot leaf's vascular bundles are conjoint, collateral, and closed, with no cambium present.
4. Roots: Root vascular tissue is arranged radially, with xylem and phloem sitting on alternating, separate radii rather than side by side on the same radius. That is a radial arrangement, not conjoint collateral, so roots do not belong on this list.

Since monocot stems and both kinds of leaves all share the conjoint, collateral, closed arrangement, while roots use an entirely different radial layout, the combination should include I, II, and III but exclude roots.

Let's summarize:

• Conjoint collateral closed bundles: monocot stems, and leaves in general (monocot or dicot), since none of these do secondary growth.
• Roots: radial vascular arrangement, a different pattern entirely.

So the correct combination is I, II, III.