>inb4 post>>11960796This study of glowing shows that there is an increase in calcium levels moving as a wave through the plant and being sensed by GFP protein modules attached to sensor proteins. Ca2+ moves through the phloem and through direct contact points from cell to cell (plasmodesmata) and activates jasmonic acid (JA) production in connected leaves. JA and other molecules act as defense hormones, and Ca2+ itself, electric signals and reactive oxygen species trigger this kind of responses in plants.
Don't forget that the same response that you see here to the caterpillar also takes place when the leaf is treated with the transmitter glutamate, which is the molecule related to the process, and not the simple pumping of water. The fact of being a defense signal is obvious here, as connected leaves start to prepare the molecular mechanisms to prime their defense responses.
It's not funny nor strange that plant responds the same way to touch, cut, and being eaten. In fact, human neurons transmit signals by sodium, and depending on the amount of neurons implied and other factors the brain interprets it as "pain". Calcium is one of the main molecules functioning as messengers in the cytoplasm of cells of any organism. You don't need different molecules for different levels of the same stimulus, but different levels/concentrations of the transmitter molecule itself.
And... no, plants do not like to be eaten. Also, plants need calcium the same way as animals. Precisely is for this kind of mechanisms functioning correctly that they need it, as long as for many other functions that calcium has in both taxonomic groups.
Please anons, I encourage you to read the article so you can understand what is really happening here:
http://science.sciencemag.org/content/361/6407/1112 
