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Difficulty: MediumLogical Inferences

In temperate forests, common mycorrhizal networks (CMNs) of fungal mycelia connect the roots of adjacent trees, enabling the subterranean transfer of carbon, water, and warning signals. When a host plant is attacked by herbivores, it releases volatile organic compounds into the atmosphere and transmits chemical warnings through the CMN, triggering defense responses in neighboring plants. However, ecologist Dr. Clara Vance demonstrated that if neighboring trees are already experiencing mild drought stress, the defense signals received via the CMN instead prompt them to conserve water by closing their stomata rather than synthesizing chemical defenses. Which choice most logically completes the text?

  1. A
    atmospheric volatile organic compounds are less effective at initiating defensive behaviors in neighboring trees than subterranean signals are.
  2. under drought conditions, receiving warnings about herbivory via mycorrhizal networks leads neighboring trees to prioritize water conservation over defensive chemical synthesis.Answer
  3. C
    mycorrhizal networks fail to transmit chemical warning signals when the host plant is undergoing drought stress.
  4. D
    neighboring trees experiencing drought stress are more vulnerable to herbivore damage than trees that are completely disconnected from the mycorrhizal network.

Answer

under drought conditions, receiving warnings about herbivory via mycorrhizal networks leads neighboring trees to prioritize water conservation over defensive chemical synthesis.
The correct option is supported because the passage states that warning signals received via the mycorrhizal network prompt neighboring trees to close their stomata and conserve water rather than synthesize defenses if those neighbors are experiencing drought stress. This directly supports the inference that drought conditions lead to prioritizing water conservation over defense synthesis when warned of herbivore presence.

Step-by-Step Solution

1
Identify the primary mechanism of plant communication described in the passage.
Host plants attacked by herbivores warn neighboring plants via chemical signals sent through mycorrhizal networks, triggering defenses in those neighbors.
This establishes the default relationship and baseline behavior under normal conditions.
2
Analyze how the introduction of drought stress alters this communication outcome.
Drought-stressed neighbors receiving the signal prioritize water conservation (closing stomata) instead of synthesizing chemical defenses.
This identifies the specific response shift described in the researcher's findings.
3
Evaluate the choices to find the one that directly matches this shift without making external assumptions.
The correct answer accurately states that under drought conditions, herbivore warnings lead neighboring trees to prioritize water conservation over chemical defense synthesis.
This matches the premises directly and avoids speculation.

Key Concept

Logical Inferences
Estimated Time:1m 30s
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Topics

Logical Inferences

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