Plant Talk: Peppers Dig Basil's Good Vibrations

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The Ents of the “Lord of the Rings” series and the flowers in “Alice in Wonderland” spoke with each other and people. In the real world, plants may have a much more subtle form of communication that borders on telepathy.

Some plants seem to use acoustic vibrations to communicate and gather information about their environment. For example, when physiologists at the University of Western Australia planted pepper seeds near basil, the seeds performed better than when planted alone. The beneficial effects continued even when sheets of plastic separated the seeds from the basil, thereby blocking any known form of communication, such as chemical or touch, as well as shared perception of the environment, such as light levels and moisture. The study was published in BMC Ecology.

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“Our results show that plants are able to positively influence growth of seeds by some, as yet, unknown mechanism,” said study author Monica Gagliano of the University of Western Australia. “Bad neighbors, such as fennel, prevent chili seed germination in the same way. We believe that the answer may involve acoustic signals generated using nanomechanical oscillations from inside the cell which allow rapid communication between nearby plants.”

Nanomechanical oscillations, or vibrations, cause sound waves to pass between the plants. The sound waves’ vibes are at a frequency inaudible to the human ear. Other research published by Gagliano in Trends in Plant Science found that corn roots produce sound in the 220-Hertz range.

Another of Gagliano’s studies found that chili peppers sprouted faster and grew faster when planted near fennel that had been blocked by a sheet of plastic. However, when the chili seeds were not blocked from the fennel, their germination rates decreased compared to peppers planted alone.

Gagliano suggested, “that light or volatile chemical signals from fennel plants must be hindering the chilli seeds’ germination rates,” in that study published in PLOS ONE. In her experiment, the plastic may have blocked the signals that hindered germination, but still allowed signals that warned the chili of the fennel’s presence, which encouraged the peppers to grow faster to avoid the fennel’s negative effects while in their weak seedling state.

Farmers and gardeners could benefit from digging the good vibrations of their floral friends. Placing mutually beneficial plants near each other, known as companion planting, may affect the vegetation in ways plant physiologists are still working to understand.

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Gardening lore holds that planting basil near crops, including peppers and tomatoes, repels some insect pests, such as white flies, tomato hornworms and aphids. Leafy basil also shades the soil and helps maintain high humidity that peppers like. Hence, evolving to grow well near basil could have survival advantages for peppers. However, basil originally evolved in India, whereas peppers sprouted first in Central and South America, so it seems unlikely that the plants evolved a specific relationship to each other.

On the other hand, gardening guides recommend against growing fennel near other crops. Gagliano seems be finding the biological basis for practices gardeners have known for years.

IMAGE: Garlic clove, red chilli pepper, basil leaves on square of white rice. (Clive Streeter and Patrick McLeavy/Getty Images)

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