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Question

Difficulty: MediumDirect Factual Retrieval

Passage:
In 1902, Austrian botanist Gottlieb Haberlandt formulated the principle of cellular totipotency, proposing that every somatic plant cell contains the complete genetic instructions necessary to regenerate a whole organism. To empirically demonstrate this concept, Haberlandt isolated fully differentiated palisade parenchyma cells from the foliar tissue of *Ornithogalum nutans* and placed them in a synthetic culture medium consisting of inorganic salts and sucrose. While these cultured cells maintained metabolic viability for extended periods—exhibiting active cytoplasmic streaming and synthesized localized cell wall thickenings—they consistently failed to undergo mitotic cell division. Haberlandt hypothesized that this developmental quiescence was not caused by an irreversible loss of cellular potency during differentiation, but rather by the absence of specific chemical signals normally supplied by adjacent vascular conduits. He posited that surrounding tissue complexes synthesized diffusible growth-promoting factors essential for triggering cytokinesis. Decades later, plant physiologists confirmed Haberlandt’s theoretical prediction by isolating auxins and cytokinins, demonstrating that exogenous supplementation of these phytohormones is required to induce proliferation in differentiated tissue. Furthermore, although Haberlandt’s initial attempts failed to achieve cell division, his rigorous implementation of sterile handling procedures established the foundational protocols for modern micropropagation and plant cell culture.

According to the passage, Haberlandt attributed the inability of his isolated parenchyma cells to undergo cell division to which of the following?

  1. A
    An irreversible loss of mitotic capacity that naturally occurs during cellular differentiation
  2. B
    The absence of essential inorganic salts and carbohydrates in the nutrient solution
  3. The lack of specific diffusible signaling substances normally provided by adjacent vascular tissuesAnswer
  4. D
    Contamination of the culture medium resulting from unsterile handling procedures
  5. E
    The complete cessation of cytoplasmic streaming and cell wall synthesis following isolation

Answer

Haberlandt attributed the failure of cell division to the absence of specific chemical signals normally supplied by neighboring vascular conduits.
The correct answer accurately restates the passage's explicit evidence. The text notes that Haberlandt believed the failure of isolated cells to divide was due to 'the absence of specific chemical signals normally supplied by adjacent vascular conduits,' which he described as growth-promoting factors synthesized by surrounding tissue complexes.

Step-by-Step Solution

1
Locate the explicit detail in the text addressing Haberlandt's attribution of developmental quiescence (failure to divide).
Found text: 'Haberlandt hypothesized that this developmental quiescence was not caused by an irreversible loss of cellular potency... but rather by the absence of specific chemical signals normally supplied by adjacent vascular conduits.'
Direct factual retrieval requires identifying explicit statements made by the author/subject in the text.
2
Match the explicit passage statement with the corresponding choice.
The statement directly corresponds to the option describing the lack of specific diffusible signaling substances provided by adjacent vascular tissues.
GMAT Reading Comprehension direct retrieval items paraphrase passage facts using semantic equivalents.

Key Concept

Direct Factual Retrieval
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Topics

Direct Factual Retrieval

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