Harsh Bais, a botanist at the University of Delaware, and a high school student collaborated to understand how plants behave when they feel threatened. They studied about a thousand Arabidopsis thaliana or mustard weed plants that were grown in the lab in petri dishes. It was found that when one plant in the petri dish was injured, the other plant grew more rapidly and developed more lateral roots in an attempt to beef up its defenses. The research team found that the plants did not communicate through soil bacteria; rather, they communicated through airborne chemicals released primarily from leaves. When an injured plant sent signals of distress the neighboring plants were observed to express more of auxin, the growth hormone, which corresponds to a malate transporter (ALMT-1) that draws beneficial bacteria from the soil. It is not known yet for how long these compounds remain in the air.
Read more in Science Daily.