It is well known that plants not only respond to their environment by manipulate it as well. They aim toward the light, they put out chemicals that inhibit the growth of competing plants, carnivorous plants respond to prey touching the "hairs", they put out sweet smelling flowers and nectar to bring in insects to assist with pollination, etc. It would be a bit of a stretch to label responding to vibrations as actual pain sensation though. Interesting research but not really a surprise as I see how the weeds in my fields are so well adapted for controlling their world.