Over billions of years, thanks to natural selection and a beautiful and peaceful neighbourhood – symbiosis* – plants have adapted to the conditions of their habitat, coexisting and complementing each other: protecting against diseases and pests, providing shade and even nutrients. And we humans can use these plant properties wisely to reduce environmental pollution from synthetic chemical plant protection products.

*Symbiosis – various forms of coexistence between different types of organisms. The word derives from the Greek word symbiosis – coexistence. Two closely related organisms in symbiosis benefit each other.

Thanks to their essential oils, aromatic plants have repellent, insecticidal, fungicidal and anti-sprouting properties, which have been successfully used to protect plants from insect pests. The role of essential oils in plant metabolism is multifaceted. Of course, one of the functions that essential oils play in a plant is as a defence against insects. As insecticides, essential oils act through the respiratory organs of pests, stopping the spread of aphids and ticks. In addition to all the properties listed above, they help defend against pathogens and other micro-organisms.

Bioactive protective substances synthesised by individual plant parts can help protect other plants from diseases and pests. As a rule, the harsher and poorer the growing conditions, the stronger the protective effect of the plant’s bioactive substances.

This unsightly inhabitant of desert and poor soils, the wormwood or bitter kite (Artemisia abisinthium L.), has insecticidal properties thanks to its active ingredient, the bitter glycoside absinthe. Bitter sorrel also contains up to 2% essential oil, which is predominantly terpenoid – oxygenated derivatives of terpenes: sabinyl acetate and thujone[1,2]). Terpenoids are the chemical communicators in plants, from pheromones to highly effective defence agents.

Based on literature:

• Judžentienė, A. and D. Mockutė, 2004. Chemical composition of essential oils of Artemisia absinthium (wormwood) growing wild in Vilnius. Chemistry, 15: 64-68.
• Estonian Acad. Sci. Chem., 2006, 55, 3, 155-165 Composition of the essential oil of Artemisia absinthium L. of different geographical origin Anne Orava* , Ain Raalb , Elmar Arakb , Mati Müüriseppa , and Tiiu Kailasa a Institute of Chemistry, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia b Institute of Pharmacy, University of Tartu, Nooruse 1, 50411 Tartu, Estonia Received 1 November 2005, in revised form 21 November 2005