Plants talk to each other
If you missed the last post about bacteria communicating and acting together like a wolfpack using underground systems to coordinate attacks, then check it out over at Wired.
But going with the theme, plants do a similar thing. They use mechanisms underground for communication and talk to each other, sort of like in Avatar. In this case, the plants are using a fungi that lives in the soil to relay messages of impending danger. A fungal-phone line.
Considering plants can’t fight, they use the fungus to send messages like “Aphids! Watch out!” and they all start secreting a scent that brings something which can fight. The sent lures wasps over which help fight off the aphids. Pretty cool right? Now you know there are tons of underground communication systems happening without you even realizing because evolution is freaking awesome.