Plant tissue culture terminology — In micropropagation and in vitro culture, what does “organogenesis” specifically refer to?

Introduction / Context:
In plant tissue culture and micropropagation, organogenesis describes the developmental process by which discrete organs such as shoots and roots are induced to form under controlled conditions. It is a core route for clonal propagation and regeneration after transformation.

Given Data / Assumptions:

• Explants or callus are grown on media with defined auxin/cytokinin ratios.
• Callus refers to an undifferentiated cell mass.
• Organogenesis yields recognizable organs (shoots, roots) rather than whole embryos.

Concept / Approach:
Organogenesis can be direct (organs arise from the explant without an intervening callus phase) or indirect (organs arise from prior callus). The hormonal balance concept is key: high cytokinin relative to auxin favors shoot organogenesis, whereas higher auxin favors root organogenesis.

Step-by-Step Solution:

Verification / Alternative check:
Protocols demonstrate that altering the auxin:cytokinin ratio switches between callusing and organ formation. The presence of meristematic centers and subsequent organ primordia confirms organogenesis.

Why Other Options Are Wrong:

Common Pitfalls:
Equating callus induction with complete regeneration; forgetting that direct organogenesis can bypass callus.

Final Answer:
Formation of new roots and/or shoots from callus or directly from explant tissues.