In the Swedish University of Agricultural Sciences laboratory, barley plants are holding quiet conversations through the air—and their neighbors are listening. Dr. Velemir Ninkovic and his team have discovered that healthy, undamaged plants continuously release their own chemical "fingerprint" into the air, and neighboring plants actively read these signals to adjust not only their defenses but their entire growth strategy, a finding that fundamentally expands our understanding of plant communication.
Until now, most research on plant-produced volatile organic compounds—carbon-based chemicals that evaporate easily into the air—focused on damaged plants releasing alarm-like chemical signals to warn neighbors to activate anti-herbivore defenses. But this new study, published in the Journal of Experimental Botany, describes a previously unrecognized role for healthy plant VOCs in competitive growing environments. These aromatic compounds, responsible for iconic fragrances like lavender and citrus, carry information far more nuanced than distress calls.
To understand this phenomenon, Ninkovic's team conducted laboratory experiments using three distinct cultivars of barley that grow at different rates: the slow "Fairytale," the intermediate "Luhkas," and the fast "Salome." Each cultivar expresses its own VOC profile. The researchers exposed the slow-growing Fairytale and fast-growing Salome cultivars to VOCs from all three types and measured the effects on their growth and defense strategies by analyzing physical properties and gene expression after 25 days.
The results revealed something striking: exposure to different VOC profiles triggered shifts in total plant biomass. Plants adjusted their growth to match the competitive pressure signaled by their neighbor's scent. They grew more when exposed to a fast-growing neighbor and less when exposed to a slow-growing one. This effect appeared consistently across all parts of the plant—leaves, stems, and roots—rather than the plant simply reshuffling resources between its parts.
Genetic analysis showed the mechanism behind this adaptation. Shifts toward the slow-growing Fairytale VOC profile were associated with an upregulation in stress-response genes that protect against herbivores and a downregulation in cellular transport and DNA replication genes. The opposite pattern held true for shifts toward the fast-growing Salome VOC profile. In other words, plants don't just hear their neighbors—they actively recalibrate their genetic priorities in response.
The specific VOCs most strongly associated with these growth signals include benzyl nitrile, linalool, and octanal—compounds that create some of nature's most beloved fragrances, alongside more metallic and earthy scents. These are everyday chemicals in plant biology, suggesting this type of communication is far more widespread than previously understood.
"Plants release a rich blend of volatile compounds as a normal part of their biology, and it would make evolutionary sense for neighbors to have developed the ability to pick up on each other's chemical signals over millions of years of co-existence," Ninkovic explains. While this study focused on barley—one of the world's most important cereal crops—the researchers believe this constitutive VOC interaction may be widespread across the plant kingdom, though the specific compounds involved and the strength of the response will likely vary greatly between species.
What emerges from this work is a portrait of plant communities far more aware and responsive than previously imagined: not broadcasting alarm to strangers, but negotiating their growth in real time with neighbors, adjusting their investments in growth versus defense based on the chemical signatures of those around them.