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Series of photographs for the book -The Art of acclimating plants, the garden of the Villa Thuret - by Catherine Ducatillion and Landy Blanc-Chabaud, published by Editions Quae. © INRA, SLAGMULDER Christian

Plants also feel, move and communicate!

External communication: odours

The cocktails of odours emitted by plants in response to aggressors may enable the early detection of attacks and the design of appropriate control strategies.

By Pascale Mollier, translated by Vicky Hawken
Updated on 09/05/2014
Published on 07/30/2014

Plants cannot flee when faced with an aggressor.  It is perhaps for this reason that they are like chemical factories, synthesising a wide variety of secondary metabolites that help to fight against insects or pathogenic agents.

The substances that serve as messengers are mainly VOC (volatile organic compounds) belonging to three main categories (terpenes, benzenoids and alcohols and aldehydes).

Defence against pests

VOC are involved in controlling a variety of insects, often by attracting their predators.

For example, it has been shown that cotton plants under attack from caterpillars will release VOCs which can attract wasps that are parasitoid to the caterpillars.

In other cases, VOCs stimulate the plant's defences and may even be transmitted to neighbouring plants in order to protect them.  Thus, using an experimental system made up of two communicating chambers, a Japanese team was able to show that bean plants attacked by mites used air currents between the two chambers to transmit to neighbouring healthy bean plants three terpenes which stimulated the defences of the latter, thus rendering them more resistant to the mites.  These defence mechanisms take the form of an increase in the synthesis of jasmonic acid and the expression of defence genes.

Bouquets of specific VOCs as pathogen detectors

Bouquets of VOCs often include several dozen detectable compounds.  The same species may emit slightly different bouquets as a function of the aggressor, while several species can emit similar bouquets versus the same stress.

In a given species, the specificity of the VOC relative to an aggressor is such that the detection of VOCs may provide information on the health status of commercial crops.  For example, it has been suggested that greenhouses could be equipped with VOC sensors to enable automatic detection of the presence of diseases before the symptoms appear.

Contact(s)
Scientific contact(s):

Associated Division(s):
Environment and Agronomy, Plant Health and Environment, Plant Biology and Breeding
Associated Centre(s):
Dijon

Odours to control cabbage maggot

INRA scientists in Rennes have studied the VOCs emitted by Brassicaceae (cabbage, broccoli, radish, turnip, rapeseed) against the larvae of cabbage maggot.  The research team selected ten or so volatile compounds: some of them modified the laying behaviour of the maggots, while others attracted their natural enemies.

These different compounds were tested successfully in the field under a push-pull strategy by means of diffusion sprayers: within cultivated plots, the compounds were sprayed to repel the flies (push), while along the margins, the devices sprayed compounds that both attracted the pests and stimulated the presence of their natural predators (pull).  This strategy proved its efficacy in protecting broccoli crops during several successive years.