Question

Why is the apical meristem tissue usually lacking the presence of plant viruses?
A. High metabolic activity in meristematic cells
B. Absence of vascular system in the meristem
C. Low endogenous auxin level
D. High concentration of sugar
Choose the correct answer from the options given below:

• A. B and D only
• B. A and B only
• C. D and A only
• D. B and C only

Hint:

The Meristem is a "Fast-Moving Target." It grows faster than the virus can travel, and it has no "Roads" (Vessels) for the virus to drive on!

Answer 1

The Correct Option is B

Concept: The distribution of viruses within an infected plant is not uniform. The shoot apical meristem is famously "sanitized" or free from viruses, a property that biotechnologists exploit to produce healthy plants from diseased ones.

Step 1: The Role of the Vascular System (B).
Viruses primarily move systemically through the plant via the phloem (vascular tissue). The apical meristem is composed of young, undifferentiated cells where the vascular system is not yet fully developed. Without these "highways" for transport, viral particles cannot easily reach the growing tip.

Step 2: Metabolic Competition (A).
Meristematic cells are characterized by high metabolic activity and extremely rapid rates of cell division. In many cases, the speed at which the plant produces new cells at the apex outpaces the rate at which the virus can replicate and spread cell-to-cell through plasmodesmata.

Step 3: Other Contributing Factors.
While not listed as the primary answers in this specific combination, high endogenous auxin levels (unlike option C) and RNA interference (RNAi) mechanisms also help the meristem defend against viral invasion. However, based on the provided choices, the combination of high metabolism and lack of vascularization is the most accurate explanation.