Q.54 Determine the correctness or otherwise of the following Assertion [a] and the Reason [r]
Assertion [a]: It is possible to regenerate a whole plant from a single plant cell.
Reason [r]: It is easier to introduce transgenes in to plants than animals.
(A) Both [a] and [r] are true and [r] is the correct reason for [a]
(B) Both [a] and [r] are true but [r] is not the correct reason for [a]
(C) Both [a] and [r] are false
(D) [a] is true but [r] is false

Answer: (B) Both [a] and [r] are true but [r] is not the correct reason for [a]

Assertion [a] holds due to plant cellular totipotency, enabling a single cell to dedifferentiate and form a complete plant via tissue culture. Reason [r] reflects practical advantages in plant genetic engineering from this totipotency. However, [r] does not causally explain [a], as regeneration precedes and enables transgene introduction but stands independently.​

Option Analysis

• (A) Both true, [r] correct reason: Incorrect; [r] describes a downstream benefit, not the cause of totipotency-based regeneration.​

• (B) Both true, [r] not reason: Correct; totipotency allows regeneration (e.g., protoplasts to plants), and it facilitates transgenesis, but ease of transgenes does not enable regeneration.​

• (C) Both false: Incorrect; both statements are biologically accurate in plant biotechnology contexts.​

• (D) [a] true, [r] false: Incorrect; transgene delivery is indeed simpler in plants via Agrobacterium or regeneration post-transformation, unlike complex animal methods.​

Plant regeneration from a single cell showcases cellular totipotency, a cornerstone of plant biotechnology making whole plant regeneration possible through tissue culture pathways like somatic embryogenesis. This assertion-reason question tests understanding of why introducing transgenes into plants surpasses animal systems, yet without direct causation. Key phrase “regenerate whole plant from single cell” highlights totipotency’s role in genetic engineering efficiency.​

Core Concepts

Totipotency means any plant cell retains full developmental potential, forming callus, embryos, or organs under auxin-cytokinin cues. Examples include carrot protoplasts yielding plants, proving [a]’s truth. Transgene introduction leverages this: transform cells via particle bombardment or Agrobacterium, then regenerate transgenics—simpler than animal embryonic stem cell targeting.​

Why [r] Succeeds in Plants

Plants permit stable germline transmission post-regeneration, avoiding animal challenges like mosaicism or ethical embryo limits. This makes [r] true, but it stems from totipotency rather than explaining it.​

Exam Relevance

Common in GATE/NEET biotech, such questions link cell biology to applications. Option (B) fits as regeneration enables transgenesis, not vice versa.​