Q.Virus free plants are developed from

Meristem culture -- growing just the virus-free apical dome of a shoot tip -- is the standard technique for producing virus-free plants.

Working

Plant viruses spread systemically through the plant mainly via the vascular tissue (phloem), and their movement into the actively-dividing shoot apical meristem is comparatively slow and often incomplete, because this region lacks mature vascular connections and has a very high rate of cell division that tends to 'outrun' the virus. As a result, even in a plant that is visibly and systemically virus-infected, the extreme tip of the shoot apex (the meristematic dome, typically 0.1-1.0 mm) is frequently free of virus particles.

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Viruses spread through a plant's vascular tissue, but the actively-dividing meristem itself has no vascular connections, so it stays virus-free.

In meristem culture (a form of micropropagation), a very small piece of the actively dividing apical or shoot-tip meristem is excised from a plant and grown in vitro on a suitable nutrient medium to regenerate a complete new plant. Although a plant may be systemically infected with a virus that has spread through its vascular tissue (xylem/phloem), the meristematic dome itself is not yet connected to this vascular system, because vascular tissue differentiates only behind the actively growing tip. As a result, virus particles cannot reach the meristematic cells, and plantlets regenerated from meristem-tip explants are consistently virus-free, even when taken from an infected parent plant. This technique is …