Odor signals in plant communities are mediated by biodiversity
Plants communicate with other organisms by releasing volatile organic compounds into their environment through their flowers, leaves, and roots. These signaling molecules attract pollinators, repel herbivores, and enable plants to communicate with each other. A research team led by Sybille Unsicker at the Max Planck Institute for Chemical Ecology in Jena and the University of Kiel investigated how plant species diversity in a community influences the chemical communication of individual plants. "Understanding how a plant's chemical signals change with plant diversity in its environment helps us to see the loss of biodiversity as more than just a loss of species. It also changes the chemical communication of an entire ecosystem," says Sybille Unsicker, who led the Plant-Environment Interactions project group at the Max Planck Institute for Chemical Ecology ( https://www.ice.mpg.de/218345/chemical-ecology-in-poplar ) and is now a professor at Kiel University's Botanical Institute.
Field experiments with ribwort plantain in the Jena Experiment
The research team focused its investigations on ribwort plantain (Plantago lanceolata) because its ecological interactions have already been well studied. It is one of the most important research plants in the Jena Experiment ( https://the-jena-experiment.de/ ). The research was conducted in the context of this project. "In our experiments, we wanted to include more than one or two neighboring plants, as is common in laboratory or greenhouse conditions. In natural ecosystems, plants live in diverse communities and interact with many other plants, insects, and microorganisms. The Jena Experiment provided the ideal conditions for our research," says first author Pamela Medina van Berkum.
The biggest challenge in outdoor experiments is measuring the volatile compounds emitted by plants. Therefore, developing a method to measure plant odors in the field was of central importance. "We designed a system that traps these odors at the community level using a transparent cage. This cage is placed over the vegetation to concentrate the odors. At the individual plant level, we took a similar approach but enclosed the plants separately in small, transparent plastic bags," explains Pamela Medina van Berkum. Using state-of-the-art analytical methods, the scientists were then able to identify and measure the quantities of the various chemical compounds.
Diverse plant communities emit more complex chemical signals
The researchers found that the more diverse the plant community, the more complex the chemical signals. High species diversity leads to the release of more volatile compounds and a greater variety of odor molecules. This change affected both individual plants and the entire plant community in the experiments. The chemical signals of a single ribwort plantain (Plantago lanceolata) were indirectly altered by neighboring plants. Thus, the odors emitted by surrounding plants influenced how individual ribwort plantain plants communicated.
Disruption of invisible communication networks due to biodiversity loss
The identity and diversity of neighboring plants influence how plants send and receive chemical signals. Changes in odor profiles have consequences because odors play a key role in communication between plants, insects, and microorganisms.
"Plant diversity has a direct impact on the co-evolution of species, the stability of ecosystems, and nature conservation. The loss of biodiversity can disrupt visible interactions between species and invisible communication networks of plants," warns Sybille Unsicker. Increasing species diversity through sustainable agriculture, such as flower strips, crop diversification, and avoiding herbicides, could help restore these natural signaling systems. This would also support natural plant defenses and the attraction of pollinators.
A new perspective on the role of biodiversity
Led by Sybille Unsicker, the researchers want to conduct further experiments to better understand how changes in chemical communication resulting from species composition affect ecosystem function. Specifically, they aim to determine how biodiversity influences the interactions between plants and other organisms, particularly with regard to insect attraction patterns. The current study highlights the remarkable diversity of volatile compounds, particularly in species-rich grasslands. However, their ecological significance is largely unknown. The research team aims to address this knowledge gap.
