Etude de la cinétique de pénétration foliaire et de l'activité systémique des huiles essentielles de citronnelle et de cannelle sur Arabidopsis thaliana (L.) Heynh., Lolium perenne L. & Trifolium incarnatum L.

Abstract

In the space of a century, the world's population has quadrupled, leading not only to an increase in global food production, but also to a rise in the use of plant protection products. Aware of the harmful effects of synthetic products on the environment and public health, many products have been withdrawn from the market in Europe since the 1990s. However, the use of synthetic pesticides cannot be restricted without finding alternatives. As far as weed control is concerned, essential oils (EOs) represent a promising alternative for the development of new biobased herbicides. Indeed, studies have shown that cinnamon and lemongrass EOs have herbicidal activities comparable to those of glyphosate. Nevertheless, the literature provides little documentation of their modes of action as bioherbicides. In order to fill these gaps, this work first provided a better understanding of how HEs penetrate the leaves of target plants after foliar application. The leaf penetration kinetics of Ceylon cinnamon (Cinnamomum verum from the bark) and Java lemongrass (Cymbopogon winterianus from the aerial part of the plant) EOs were studied in the model plant A. thaliana. Follow-up quantification by gas chromatography coupled to a flame ionization detector (GC-FID) demonstrated the ability of the majority compounds of both EOs to penetrate the various leaf tissues. In addition, the results showed the ability of trans-cinnamaldehyde, citronellol, citronellal and geraniol to penetrate the inner leaf tissues in less than three hours. In addition, this work demonstrated for the first time the systemic activity of cinnamon and citronella EOs in T. incarnatum and L. perenne, following root and leaf penetration. A quantitative method based on gas chromatography-mass spectrometry (GC-MS) was developed and used to analyze hydroponically grown plants to study root penetration, as well as soil-grown plants to assess foliar penetration. This approach revealed the predominant essential oil compounds in plant organs to which the EOs had not been directly applied. In particular, cinnamon EO showed significant herbicidal action via root penetration on hydroponically grown plants. In the case of lemongrass, no herbicidal action was observed by this route. Nevertheless, the potential presence of a geraniol detoxification pathway by the plant is envisaged. In addition, both EOs showed a contact herbicidal action a few minutes after foliar application on soil-grown plants. In conclusion, this work confirms the potential of Ceylon cinnamon and Java lemongrass EOs as bioherbicides.