Question

Arrange the following in centripetal manner in woody dicot stem:
I. Phellum
II. Secondary Phloem
III. Phellogen
IV. Secondary Xylem
V. Phelloderm
VI. Vascular Cambial ring

• A. IV, VI, II, V, III, I
• B. IV, III, II, I, IV, V
• C. I, III, II, IV, V, VI
• D. I, III, V, II, VI, IV

Hint:

In woody dicot stems, from outside to inside: Phellum → Phellogen → Phelloderm → Secondary Phloem → Vascular Cambium → Secondary Xylem.

Answer 1

The Correct Option is D

Step 1: Understanding centripetal arrangement.
Centripetal arrangement refers to the order of tissue layers from the outside (periphery) toward the center of the stem in woody dicot plants.

Step 2: Identify tissues from periphery to center.
- Outermost layer: Phellum (cork)
- Beneath phellum: Phellogen (cork cambium)
- Beneath phellogen: Phelloderm (produced inward by cork cambium)
- Next: Secondary Phloem (produced outward by vascular cambium)
- Vascular Cambial ring: produces secondary xylem inward and secondary phloem outward
- Innermost: Secondary Xylem (wood)

Step 3: Arrange tissues centripetally.
From periphery to center: \[ \text{Phellum (I)} \rightarrow \text{Phellogen (III)} \rightarrow \text{Phelloderm (V)} \rightarrow \text{Secondary Phloem (II)} \rightarrow \text{Vascular Cambium (VI)} \rightarrow \text{Secondary Xylem (IV)} \]

Step 4: Conclusion.
Hence, the correct centripetal arrangement is: I, III, V, II, VI, IV