Practice question

Dedifferentiation represents reversal of differentiated cell to meristematic, less specialized state capable of renewed division and subsequent redifferentiation into alternative cell types. In vivo, mature specialized cells such as leaf mesophyll or phloem parenchyma that have exited cell cycle and acquired secondary walls, vacuoles, and specific metabolite profiles are induced by wounding or growth regulators to lose specialization traits: they reduce vacuolation, enlarge nucleus, regain dense cytoplasm, and reactivate cell cycle genes cyclin-dependent kinases and cyclins D. In tissue culture, high auxin to low cytokinin ratio triggers this transition forming callus from differentiated explant within days. Dedifferentiated cells express stem-cell markers and become pluripotent intermediate that can be reprogrammed into new organs via organogenesis. Process involves epigenetic resetting including DNA demethylation, histone acetylation, and downregulation of differentiation genes, enabling plants to regenerate after injury and forming basis for vegetative propagation, graft wound healing, and tissue culture morphogenesis and clonal multiplication for crop improvement and conservation.