Allelopathy is the release of organic chemicals that help or harm plants growing nearby by a plant. What is really interesting is that these allelochemicals are not used by the plant except to influence other plants.
One of the best known cases of this happens with walnut trees. Walnut trees produce hydojuglone. When hydrojuglone is exposed to oxygen it causes anything from wilting to death in plants near the walnut tree.
While digging around the net learning about allelopathy I started to wonder just how smart plants might be and stumbled upon: Aspects of Plant Intelligence a paper published in the Annals of Botany in 2003
The more we learn about plants and the chemical signaling inside and sent out from the plant, the less like vegetables they appear to be.
The paper is very readable, you won’t need a science degree to dig through it and worth a read. You’ll not look at your plants the same way again.