Look up elicitor in Wiktionary, the free dictionary.
Elicitors, in biology, are compounds that when introduced into a living organism signal the activation or synthesis of another compound. An example of such a molecule is jasmonic acid, which stimulates the biosynthesis of delta-viniferin in grapevine cell cultures. Another example is chitosan which is used in agriculture as a natural biocontrol agent. Effectors differ from hormones, compounds produced in one part of an organism to cause a change in another part of that organism, in that they do not have to be produced within the organism that they are eliciting a response in, and are usually not naturally occurring in the organism.
^Effects of Elicitors on the Production of Resveratrol and Viniferins in Cell Cultures of Vitis vinifera L. cv Italia. Anna Rita Santamaria, Nadia Mulinacci, Alessio Valletta, Marzia Innocenti and Gabriella Pasqua, J. Agric. Food Chem., 2011, 59 (17), pages 9094–9101, doi:10.1021/jf201181n