Waft

Pulse draws a real signal traveling inside one plant. This room draws a different signal: airborne, and between two plants that share no roots, no soil, no wire of any kind. When something bites, cuts, or otherwise wounds a leaf, the wound doesn't only hurt that plant — it releases a cloud of volatile organic compounds into the air, and a neighbor downwind picks them up without ever being touched.

Engelberth, Alborn, Schmelz & Tumlinson exposed intact corn seedlings to the green leaf volatiles a damaged neighbor gives off — the same six-carbon compounds behind the smell of a fresh-cut lawn — and found the exposed seedlings didn't fully activate their own defenses on the strength of the smell alone. What changed was readiness: seedlings exposed first, then actually damaged afterward, produced substantially more jasmonic acid and defensive volatile sesquiterpenes than seedlings meeting the same attack cold. The airborne signal doesn't defend a plant. It primes it.

That's not only a lab result. Karban, Baldwin and colleagues clipped wild sagebrush growing beside wild tobacco in the field and watched the unclipped, untouched tobacco raise its own defensive enzyme activity within days — and across three separate field seasons, tobacco with a clipped neighbor suffered measurably less real damage from grasshoppers and cutworms than tobacco left with an unclipped one. Different plants, a different airborne signal, the same shape: a wound nobody shared still changed what happened next door. Try both halves of that story below.

Honest gap: real volatile transit and the defense response it primes both run on the order of minutes to hours, not the couple of seconds this room takes — and neither paper publishes a continuous curve of how fast readiness actually builds, so the ramp you watch is a plain illustrative shape, not digitized data, the same liberty thaw and touch already take with their own slower mechanisms. Priming is drawn here as a switch, on or off, when the real effect is graded — it scales with how much volatile a plant actually absorbs and for how long — and it never fades in this room, though a real primed state almost certainly doesn't last forever either, since neither citation says how long it holds. The two seedlings pictured aren't the pairing either paper actually studied: Engelberth's mechanism comes from corn exposed to green leaf volatiles in a lab; Karban's field evidence comes from wild sagebrush and wild tobacco, signalling with a jasmonate relative instead, not a green leaf volatile at all. Both are real evidence for the same phenomenon — airborne priming between plants — but neither paper is the source for the other half of this room.

Sources: Engelberth, Alborn, Schmelz & Tumlinson, Airborne Signals Prime Plants Against Insect Herbivore Attack, Proceedings of the National Academy of Sciences 101(6):1781–1785, 2004. Karban, Baldwin, Baxter, Laue & Felton, Communication Between Plants: Induced Resistance in Wild Tobacco Plants Following Clipping of Neighboring Sagebrush, Oecologia 125(1):66–71, 2000.