Biologist Natacha Bodenhausen and colleagues analyzed the naturally occurring bacterial communities associated with leaves and roots of wild Arabidopsis thaliana, a small flowering plant. The researchers found many of the same bacterial genera in both the plants’ leaves and roots. To explain this, the researchers pointed to the general proximity of A. thaliana leaves to the ground and noted that rain splashing off soil could bring soil-based bacteria into contact with the leaves. Alternatively, the researchers noted that wind, which may be a source of bacteria in the aboveground portion of plants, could also bring bacteria to the soil and roots. Either explanation suggests that ______
Which choice most logically completes the text?
Explanation
Context: Same bacterial genera found in BOTH leaves and roots of A. thaliana. Explanation 1: rain splashes soil bacteria onto leaves. Explanation 2: wind brings bacteria both to aboveground leaves AND to soil/roots. EITHER explanation suggests something about the source. The blank states what both explanations share.
Answer: B) some bacteria in A. thaliana leaves and roots may share a common source...
Why? In explanation 1, rain carries soil bacteria to leaves — same source (soil) for both root and leaf bacteria. In explanation 2, wind serves as a common vehicle for both locations. Either way, B captures the shared-source implication.
Traps:
- A) wind-carried bacteria less beneficial than soil bacteria → neither explanation makes claims about relative benefit
- C) many leaf bacteria deposited by means other than rain → explanation 1 proposes rain; explanation 2 proposes wind; neither says non-rain means are predominant
- D) leaves and roots especially vulnerable to harmful bacteria → neither explanation discusses harmful bacteria or vulnerability