Do plants suffer when bitten (but not when slapped)?

A nice meeting I recently attended reminded me the common question if plants suffer or not when eaten. What follows should be somehow interesting for the vegetarian people crowding this blog. Interestingly, today we were shown how plants can tell the difference between a wind slap and a caterpillar bite. Yes, no joke. Strong rain or wind or other abiotic events damaging the plant body will not rise the same responses caused by cows or parasites (or human beings) chewing their leaves. If we define pain as the information that something is going wrong in our body, well, plants do feel pain too when chewed.