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Difficulty: Very hardExplicit Details

In their study of the high-altitude plant *Ranunculus glacialis*, botanist Dr. Sylvia Vance and her team examined how cellular adaptations prevent freezing damage at extreme elevations. The researchers observed that while the accumulation of soluble sugars in vacuoles lowers the freezing point of intracellular fluids, it does not prevent extracellular ice formation. Instead, the plant relies on apoplastic proteins to safely template the crystallization of ice in extracellular spaces, thereby preventing ice crystals from penetrating the cell membranes. Crucially, the team noted that this apoplastic protein production remains constant across different elevations, whereas vacuolar sugar concentrations vary dynamically in direct response to local diurnal temperature fluctuations.

Based on the text, what is true of the apoplastic proteins produced by *Ranunculus glacialis*?

  1. A
    Their production levels fluctuate dynamically in response to daily temperature changes.
  2. B
    They prevent ice from forming in both intracellular and extracellular environments.
  3. They are produced at levels that do not vary across different elevations.Answer
  4. D
    They migrate into cell vacuoles to lower the freezing point of intracellular fluids.

Answer

The apoplastic proteins are produced at levels that do not vary across different elevations.
The correct answer is supported by the text's explicit statement that apoplastic protein production 'remains constant across different elevations,' which directly corresponds to the idea that these protein levels do not vary across different elevations.

Step-by-Step Solution

1
Locate references to apoplastic proteins within the text.
The text mentions that the plant relies on apoplastic proteins to safely template ice crystallization in extracellular spaces, and that this production remains constant across different elevations.
To identify the explicit details provided about the target entity.
2
Match the explicit detail about protein production constancy to the options.
The detail that production remains constant across different elevations matches the option stating they are produced at levels that do not vary across different elevations.
To find the correct option directly supported by the text.

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Explicit Details
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