The powerful scent – how plants defend themselves

[Translate to Englisch:] © BIOP

Monoterpenes, originally discovered in coniferes, not only deliver the popular smell of the forest. They also carry out a crucial role for plant survival. Scientists of the Helmholtz Zentrum München have described this role now and published the results in the scientific journal „The Plant Cell“.

For the first time, the team of group leader Dr. Corina Vlot-Schuster from the Institute of Biochemical Plant Pathology (BIOP) of the Helmholtz Zentrum München was able to prove that volatile compounds from coniferes can also activate an immune response in bacterial infested plants and that they can also function as warning signal for neighbouring plants. The work was done in the model plant Arabidopsis thaliana (small tale cress). „We found that the monoterpenes* α-Pinene and β-Pinene activate a cascade of defense reactions in plants which are infested by pathogens“, Vlot-Schuster explains. „Subsequently, an array of defense mechanisms is started: The Salicylic acid – dependend immune response of the plant is increased. More reactive oxygen species like oxygen radicals are produced, and pathogen-related genes are stronger transcribed.“. „These are clear systemic defense reactions of a plant“, Prof. Dr. Jörg-Peter Schnitzler, head of the research unit Environmental Simluation (EUS) of the HMGU, adds. „In the course of these analyses, we could also show that plant tissues situated far away from the pathogen, can still be alarmed and be prepared for an attack.“

The ‚Cry-for-Help‘-Principal

Related volatile organic compounds are well known from the plant defense against insects. For example, it is described that plants release a certain odor after caterpillar attack which attract ichneumon flies. Those will lay their eggs in the caterpillars and therby free the plants from the pathogens. „The principal known as ‚Cry-for-Help’ also works in the case of bacterial infection“, Marlies Riedlmeier, PHD student at the BIOP and, together with her colleague Marion Wenig and Andrea Ghirardo, a research scientist at EUS, first author of the study, explains. „The difference is that in this situation also the internal, systemic defense mechanisms are activated“, she continues. „And in addition, neighbouring plants will be in a state of alarm to be prepared optimally for a bacterial infection“, Andrea Ghirardo adds. „Our results etend the ‚Cry-for-Help‘ principal, until now only described for the interaction between plants and insects to the interaction between plants and their living environment.“

The future of plant protection

Herbs, known to contain a lot of etherical oils, also release monoterpenes and thereby may potentially activate the defense mechanisms of neighbouring plants in case of an infection. The resistance gained during these defense mechanisms can protect against a broad spectrum of pathogens and thus, it has the character of a vaccination. „We do believe that the principal of signal transduction will have an increasing role for plant protection in the future“, Vlot-Schuster says.

Further information

Original publication:
Riedlmeier, M. et al. (2017): Monoterpenes Support Systemic Acquired Resistance within and between Plants,  DOI: 10.1105/tpc.16.00898