I read a short story long ago about a scientist experimenting with plants.
The scientist found that plants would react to murder or torture being carried out on people, and used that effect to help catch at least one murderer.
The short story is obviously intended to be humorous.
The scientist is explaining how he helped catch the killer, and explains that he needed a very long plant to make a directional detector.
The story ends with a play on words. The scientist caught the killer because he "heard it through the grapevine."
This is science fiction - scientist using cutting edge technology to carry out a task.
It would have been written/published in the 1960s or 1970s.
I'm pretty sure it was inspired by Cleve Backster's experiments using a polygraph on plants.
The story may also tie in with the song "I Heard It Through The Grapevine" that was popular in the late 1960s.
Does anyone know the title of the story, who wrote it, and in what collections it was published? I'd like to read it again.