Even without nerves, plants can sense when something touches them and when it lets go, a study has found. In a set of experiments, individual plant cells responded to the touch of a very fine glass rod by sending slow waves of calcium signals to other plant cells, and when that pressure was released, they sent much more rapid waves. While scientists have known that plants can respond to touch, this study shows that plant cells send different signals when touch is initiated and ended.
Source: sciencedaily