Question

Open vascular bundle and secondary growth are present in:

• A. Monocot stem
• B. Monocot root
• C. Dicot stem
• D. Dicot leaf

Hint:

Remember the sequence: Open vascular bundle $\Rightarrow$ Cambium present $\Rightarrow$ Secondary growth possible $\Rightarrow$ Typical feature of dicot stems.

Answer 1

The Correct Option is C

Concept: Vascular bundles are the conducting tissues of plants and consist of xylem and phloem. Depending upon the presence or absence of cambium between xylem and phloem, vascular bundles are classified as open or closed. An open vascular bundle contains cambium, whereas a closed vascular bundle lacks cambium. Since cambium is a meristematic tissue capable of producing new vascular elements, open vascular bundles can undergo secondary growth. Secondary growth is the increase in the girth or thickness of plant organs due to the activity of lateral meristems such as vascular cambium and cork cambium.

Step 1: Understanding Open Vascular Bundles
In an open vascular bundle, a strip of cambium is present between xylem and phloem. The cambium continuously divides and forms secondary xylem towards the inner side and secondary phloem towards the outer side. Therefore, open vascular bundles are directly associated with secondary growth.

Step 2: Analysis of Monocot Stem
Monocot stems possess scattered vascular bundles. These bundles are closed because cambium is absent. Since cambium is absent, secondary growth generally does not occur. Hence, Option (A) is incorrect.

Step 3: Analysis of Monocot Root
Monocot roots generally do not show significant secondary growth because vascular cambium is either absent or poorly developed. Therefore, Option (B) is incorrect.

Step 4: Analysis of Dicot Stem
Dicot stems possess open vascular bundles arranged in a ring. The cambium remains active and produces secondary vascular tissues. Consequently, secondary growth occurs and increases stem thickness. Thus, Option (C) is correct.

Step 5: Analysis of Dicot Leaf
Leaves generally do not undergo secondary growth like stems. Hence, Option (D) is incorrect. Conclusion: Open vascular bundles and secondary growth are characteristic features of dicot stems. \[ \boxed{\text{(C) Dicot stem}} \]