Mythbusters cannot disprove scientific experiments that took years to complete. I like that show, but in the time they have they have disproved things that are actually true and proved things that are false. So I wouldn't take their word as the end all beat all.

I also know what episode you are talking about, when they played the different types of music in controlled groups of plants in separate greenhouses.

However with time lapsed photography they have shown how trees act when another tree close to them is getting cut down. First the trees tremble, then they lean in towards the tree that is being cut down, and right before it falls they lean back.

Also there was a study done about how plants communicate and what they might communicate, the whole movie "the Happening" was based on that study.