SAT Reading & Writing · Command of Evidence (textual)
Parasitic dodder plant seedlings have been observed growing directionally toward nearby host plants before making any physical contact…
Parasitic dodder plant seedlings have been observed growing directionally toward nearby host plants before making any physical contact with them. A researcher proposes that the seedlings are responding to airborne chemical cues released by the host plant. Which finding would most directly support the researcher's proposal?
Answer and explanation
Answer: B: In controlled experiments, dodder seedlings grew directionally toward a source of tomato plant volatile chemicals even when no physical tomato plant was present at all, ruling out physical or visual…
The researcher's proposal specifically requires that airborne chemicals alone, without any physical plant present, can direct the seedling's growth. B directly supports that by isolating the chemical cue from the physical plant entirely and still observing directional growth, ruling out competing explanations like physical contact or visual cues. A describes a later stage of the interaction, not the mechanism behind initial directional growth. C and D are general background facts about dodder that don't address the specific cue-detection mechanism.
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