[Campbell Biology P.448] Refer to the 'WHAT IF?' question in Figure 19.2: 'If Beijerinck had... | Practice Question

Refer to the 'WHAT IF?' question in Figure 19.2: 'If Beijerinck had observed that the infection of each group was weaker than that of the previous group and that ultimately the sap could no longer cause disease, what might he have concluded?'

  • A: The infectious agent was a replicating organism, but its virulence decreased over time.
  • B: The disease was caused by a finite amount of a toxin, not a replicating agent.
  • C: The filter used was ineffective and allowed bacteria to pass through, but the bacteria were slowly dying.
  • D: The plant's immune system was becoming stronger with each infection, eventually eliminating the pathogen.

Explanation

If the infection became weaker and eventually ceased, it would suggest that the infectious agent was not replicating within the plant. Instead, a finite amount of the disease-causing substance like a toxin would be diluted with each transfer until it was no longer potent enough to cause disease.