Callus biology — The reversion of mature, specialized plant cells to a meristematic, dividing state that leads to callus formation is called what?
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ARedifferentiation (specialized cells forming specialized tissues)
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BDedifferentiation (mature cells reverting to a meristematic state)
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CEither a or b (they are synonymous)
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DNone of these
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ETransdifferentiation (direct switch between mature cell types without a progenitor state)
Answer
Correct Answer: Dedifferentiation (mature cells reverting to a meristematic state)
Explanation
Introduction / Context:Dedifferentiation and redifferentiation are paired concepts in plant regeneration. Dedifferentiation first produces callus from mature tissues; subsequent redifferentiation gives rise to organs or embryos.
Given Data / Assumptions:
- Explants originate from mature organs.
- Hormone regimes trigger cell cycle re-entry and loss of specialized features.
- Later stages direct formation of shoots/roots or somatic embryos.
Concept / Approach:Define terms precisely: dedifferentiation = specialized to unspecialized; redifferentiation = unspecialized to specialized. The phenomenon described (mature cells returning to a meristematic state and forming callus) matches dedifferentiation.
Step-by-Step Solution:
Map description: mature → meristematic → callus.Select the term that fits: dedifferentiation.Note that redifferentiation occurs later during organ or embryo formation.Verification / Alternative check:Histological sections of induced callus show small, isodiametric, actively dividing cells typical of dedifferentiation.
Why Other Options Are Wrong:
a) Redifferentiation is the opposite stage.c) The terms are not interchangeable.d) Incorrect; a precise term exists.e) Transdifferentiation skips the callus-like stage.Common Pitfalls:Using “redifferentiation” for early callus; reserve it for organ/embryo formation.
Final Answer:Dedifferentiation (mature cells reverting to a meristematic state).