Come on, you can do better.

On the wikipedia page you linked, there is exactly zero occurrence of the word "pain".
The only part that could remotely be linked to your previous argument does not indicate pain at all.

The GLVs responsible for the smell of freshly cut grass play a role in plant communication and plant defence against herbivory, functioning as a distress signal warning other plants of imminent danger and, in some instances, as a way to attract predators of grass-eating insects.

This paragraph is a less sensational and more serious reformulation of the source material, an opinion piece stating the following without a single scientific reference

Trauma, that’s what. It’s the smell of chemical defenses and first aid. The fresh, “green” scent of a just-mowed lawn is the lawn trying to save itself from the injury you just inflicted.

This piece was posted in May 2012 on mentalfloss.com, so not really a scientific study.

Also, nothing in there speaks of the brocoli, which you first referred to.

Edit: spelling, formatting