Scent messages

Plants constantly release small amounts of volatile organic compounds (VOCs) through their leaves. These substances can deter predators, but can also attract them. If a plant is injured by a predator, for example, the plant changes the composition of the substances released. This new mixture can then attract the predators' enemies (herbivore-induced plant volatiles, HIPVs).

Research into biocommunication offers exciting opportunities, particularly for biological plant protection. With the knowledge of plant scents, researchers can develop new methods to recognise plant diseases at an early stage or ward off pests in a targeted manner.

At the University of Zurich, Prof Meredith Schuman's team is researching how fragrances can be used as diagnostic biomarkers to detect diseases in plants at an early stage. The research group is developing a drone with which they can collect odours in the field. If their project is successful, the method could be used to build a sensor. If this sensor registers alarm odours in the field, the farmer can combat the pest at an early stage and in the right place.

Another exciting area of research is dedicated to the question of how quickly plants can adapt to changing environmental conditions. Prof. Florian Schiestl and Dr. Sergio Ramos from the University of Zurich were able to show that the effects of pollinator insects and those of herbivores are strongly interrelated. For their study, they used turnip rape (Brassica rapa), a close relative of oilseed rape, as well as bumblebees and butterfly caterpillars as interaction partners. Over six generations, they treated the plants in four different groups: with bumblebees alone or together with caterpillars, and hand-pollinated without or with caterpillar feeding. This “experimental evolution” showed that the plants pollinated by bumblebees without caterpillars were the most attractive for the pollinators - they were more fragrant and had larger flowers. Plants treated with bumblebees and caterpillars, on the other hand, were less attractive. They had higher concentrations of toxic repellents, less flower fragrance and tended to have smaller flowers. Instead of investing energy in showy flowers, they focused more on defence. At the same time, they showed an increased tendency to self-pollinate.

These results emphasise how important the interactions between plants and their environment are for their development. If the composition of the interaction partners changes - whether due to habitat loss, climate change or the disappearance of pollinators - rapid evolutionary adaptations in the plants can be triggered. The diversity of plants and their odorants still harbours many undiscovered possibilities that could be used for agriculture and nature conservation in the future.