Plant Trivia : Communication of plants

Is it true that plants also communicate each other?



There are some plants which release a certain kind of material from the leaf eaten by insects, etc. It seems plants send harmful insect warning to plants around by releasing material. 
The material = harmful insect warning is transmitted to the surrounding plants, and the substance bug doesn't like in the surrounding plants comes to become a high density.


Poplar and white birch are known as such plants which release some kind of materials and are communicating.