Don't plants move their leaves to follow the sun?
Yes. This indicates that plants have the ability to react to an outside stimulus. However, a simple response to an outside stimulus does not, in and of itself, indicate the ability to feel pain. As an example, an electric doorbell can also respond to an outside stimulus. It detects the pressure of a human finger, and it responds by ringing. However, the fact that the doorbell can react this way to the presence of your finger does not imply that the doorbell is conscious. Similarly, the ability of plants to move their leaves to follow the sun does not, in and of itself, indicate consciousness.