The smell of fresh-cut grass is a chemical alarm. The episode follows airborne plant signals, including green leaf volatiles, terpenoids that summon a herbivore's enemies, and the hormones methyl jasmonate and methyl salicylate that prime defenses. It holds a careful line between plants actively signaling and neighbors merely eavesdropping, and between lab and wild forest.
Who's who
- Ian BaldwinChemical ecologist; co-author of the 1983 talking-trees paper
- Jack SchultzChemical ecologist; Baldwin's co-author on the 1983 study
- Richard KarbanUC Davis ecologist known for field studies of sagebrush signaling
- Ted Turlings+1 more episodeChemical ecologist who showed attacked plants recruit herbivores' enemies
- Marcel Dicke+1 more episodeResearcher who helped establish indirect plant defense
Timeline
- 1983Baldwin and Schultz report damaged plants trigger defense changes in neighbors, dubbed "talking trees"
- 1990sTurlings, Dicke and others establish indirect defense via predator-attracting volatiles
- 2000Karban and colleagues report wild tobacco near clipped sagebrush suffers less damage
- 2005Maize roots shown to release a compound recruiting insect-killing nematodes
- 2006Karban and Baldwin show airborne priming between plants in the field
- 2023Science study details how methyl salicylate is perceived and converted to salicylic acid
Still debated
Whether airborne signaling is true communication or neighbors simply eavesdropping is the central dispute, with most careful researchers leaning toward eavesdropping. How much any of it matters in complex wild forests, and whether plants favor relatives, remain open.