Q.Which part of the plant is best suited for making virus-free plants and why?
Meristem culture — using the shoot apical meristem — is the most reliable method for producing virus-free plants because meristem cells are free from viral infection.
In plant tissue culture, the goal of producing virus-free plants is critical, especially for crops like potato, sugarcane, banana, and many ornamentals. Viruses are systemic pathogens — they spread through the plant’s vascular tissues, but they do not invade every cell equally. The key lies in understanding where viruses cannot reach.
The shoot apical meristem — the tiny dome of actively dividing cells at the tip of a shoot — is the part of the plant best suited for this purpose. Why? Because meristem cells divide so rapidly that viruses, which replicate more slowly, cannot keep up. Moreover, these cells lack well-developed vascular connections (xylem and phloem) through which viruses typically travel. As a result, the meristem remains virus-free even when the rest of the plant is heavily infected.
This technique is called meristem culture or shoot-tip culture. It is a standard method in plant biotechnology for disease elimination.
The process is straightforward: a tiny piece of the shoot tip (often just 0.1–0.5 mm) is excised under sterile conditions and cultured on a nutrient medium. The meristem then develops into a plantlet, which can be multiplied and tested for virus absence. This method is especially valuable for vegetatively propagated crops, where viruses accumulate generation after generation.
The smaller the meristem explant, the higher the chance of obtaining a virus-free plant — but also the harder it is to culture. A balance must be struck between size and survival.
Other plant parts like leaves, stems, or roots are unsuitable because they contain differentiated cells with mature vascular connections, making them vulnerable to viral infection. Even if a leaf appears healthy, it may harbour latent viruses. Only the meristem’s unique combination of rapid division and poor vascular connectivity guarantees freedom from viruses.
In short, the shoot apical meristem is the best part for making virus-free plants because its cells are naturally free from viral infection due to rapid division and lack of vascular connections, and this is the basis of meristem culture used in plant biotechnology.
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