Abundant surface resins present on Middle Devonian land plants

Plant resins, serving various essential ecological functions, have traditionally been associated with conifers and angiosperms. Previously, the oldest known resin was identified in the late Carboniferous. Here we reveal that substantial amounts of diterpenoid resins were already present on the surfaces of Middle Devonian land plants. These surface resins, preserved alongside plant cuticles, are rich in nonvolatile tetracyclic diterpenoids and likely played a crucial role in facilitating terrestrial colonization by forming an antitranspirant barrier on the surfaces of early herbaceous plants. These findings not only markedly push back the timeline for the emergence of the earliest resin-producing plants, but also provide valuable insights into the adaptive strategies of early terrestrial flora. Moreover, our results suggest an evolutionary transition from surface to internal resins, revealing a more complex history of resin biosynthesis than previously recognized. Analysis of Middle Devonian plant cuticles reveals abundant surface resins, markedly pushing back the origin of plant resin production and demonstrating that these resins played a key role in early plant adaptation to terrestrial environments.