Plants Smell Terpenes

Did you know that plants communicate with each other using small molecules, including the molecules called terpenes that make up the composition of essential oils? These small molecules are known collectively as Volatile Organic Compounds (VOCs). We’ve written about VOCs in previous articles: “Rose plant communication helps other plants,” “Evolution of spiders to take advantage of essential oils,” and “Terpenes in the air.” However, we haven’t talked about how the plants actually sense VOCs.

The study into how plants sense VOCs is still in its infancy. A theory by professor Kenji Matsui from Yamaguchi University in Japan is that plant “olfaction” actually happens during the regular process of photosynthesis. Photosynthesis is the molecular process by which plants create energy from sunlight. A crucial part of photosynthesis is gas exchange between the leaves and the outside air. As the plant “breathes” in air, airborne VOCs inevitably enter the leaves.

Leaves have small pores called stoma that allow air to enter the space between cells, called the intercellular space. From the intercellular space, and depending on chemical parameters, the VOCs can then enter the cells. Within the cells, VOCs are subject to several types of biochemical manipulation prior to their metabolism by the cell.  Many of these processes are still being discovered.

The final metabolism of VOCs is how the plant ultimately “smells” the aromatic cues, according to Matsui. VOC metabolism has varied effects on the plant, including serving as an early-warning signal for protecting neighboring plants from predators. This is but another example of the amazing natural effects of essential oils. 

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