Question

Which of the following is absent in monocot stem? ____.

• A. Phloem
• B. Cambium
• C. Xylem
• D. Pith

Hint:

Remember: - Dicot stem = Open bundles = Cambium Present $\rightarrow$ Can form wood. - Monocot stem = Closed bundles = Cambium Absent $\rightarrow$ Cannot form wood.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Stem anatomy varies widely across seed plants, with monocotyledonous structures lacking specific lateral meristematic tissue required for secondary widening.

Step 2: Detailed Explanation:
In a monocot stem, the vascular bundles are conjoint, collateral, and closed. They are described as closed because they entirely lack cambium tissue between the xylem and phloem. Because this lateral meristemic cambium strip is absent, monocot stems are incapable of undergoing normal secondary growth (thickening), which keeps their stems uniformly slender over their lifespan (e.g., in Grass, Maize, Bamboo). Monocot stems also lack a distinct central pith, as the vascular bundles are scattered throughout the ground tissue, making cambium the primary anatomical layer absent from the vascular system.

Step 3: Final Answer:
Cambium is absent in the vascular bundles of a monocot stem.

Answer 2

Monocot stems have vascular bundles with a specific set of features, so checking whether each listed tissue is present or absent in that anatomy will reveal what is genuinely missing.

1. Phloem: is present in every vascular bundle of a monocot stem, since it is one half of the conducting tissue responsible for transporting food, so this tissue is not absent.
2. Cambium: A monocot stem's vascular bundles are described as "closed," meaning there is no strip of dividing cambium tissue between the xylem and phloem. Without cambium, the stem cannot add new vascular tissue over time, so it never undergoes secondary (thickening) growth. This absence of cambium is the specific anatomical gap the question is pointing to.
3. Xylem: is also present in every vascular bundle, forming the other half of the conducting tissue that transports water and minerals, so it cannot be the missing component.
4. Pith: while it is true that monocot stems have scattered vascular bundles rather than a clearly defined central pith region, some ground tissue is still present around the bundles; the more definitive, textbook-recognised absence in monocot stem anatomy is the missing cambium layer within the bundles themselves.

Working through each tissue confirms that the one genuinely and consistently missing from a monocot stem's vascular bundles is cambium.

Therefore, the correct answer is Cambium.