Plant-tastic Chemical Signals


During this time of year, I often find boxes and boxes of fruits and vegetables on the kitchen counter as I come home from school. My parents are both avid gardeners, and I often hear them discussing methods in which they can improve their garden. They have attempted everything from hanging CDs on the peach tree to scare off birds, to wrapping plastic around the bases of young trees to protect them from animals. Unfortunately, my parents are often unable to protect them from their greatest threat: insects. (Dun dun dun…)

Plants, however, may be able to fortify themselves against insects to an extent. An interesting article in Scientific American suggests that a plant is able to “warn” its neighbors when that plant has been infested with harmful insects. One study involved testing caterpillar preference on several willow trees. Researchers observed that caterpillars were less likely to feed on the leaves of willow trees that were near trees already infested with caterpillars. I was surprised by this, as the trees nearby should be the next nearest food source. Since the trees were not physically connected or related in any way, it was proposed that they emitted some sort of signal. Later findings suggested that the damaged plant releases a gas to unharmed plants, which results in an increased defense against dangers.

For the past few years, Martin Heil and his research team at the Center for Research and Advanced Studies have been studying the behavior of lima bean plants. When lima bean leaves are being eaten by beetles, the plant releases both a chemical signal and produces nectar that attracts other beetle-eating insects. In order to observe the chemical signals more closely, the researchers devised an experiment in which infested lima bean plants interacted with lima bean plants. After choosing specific leaves to monitor, they used gas chromatography and mass spectrometry techniques that allowed them to identify the chemicals in the released into the air. The researchers found that the healthy and half-eaten leaves of the same plant produced the same chemical, while the control, a leaf from a plant isolated in the experiment, had no scent. Strangely enough, the leaves of the healthy plant also produced the same chemicals, and were less likely to be eaten by the beetles!

Are plants “selfless” enough to warn other plants against attack? Or is the chemical signal produced by an “injured” leaf meant for the remaining leaves of the same plant, and this signal just happens to be picked up by a neighboring plant? This was the question that researchers hoped to answer in a second experiment, one in which the leaves were isolated from one another in plastic bags. This time, only the attacked leaf produced the scent. When the scent was blown towards the other leaves on the plant, those leaves began producing the scent as well. The results demonstrated that the chemical signals were meant for the other leaves of the same plant, not other plants. However, nearby plants take advantage of this warning to maintain their own wellbeing.

Even if my parents find a new way to solve the insect problem, our garden will still be filled with a variety of plants, insects, animals, and microorganisms. In this way, our garden is like a community, a mini-ecosystem in which all of these organisms can coexist. As we learned in our reading, this interdependency is what enables each species to survive. Insects and animals depend on plants, just as plants depend on insects and animals. Plants also depend on other plants, and this article made me realize the extent to which they can communicate.

About Mr. Mohn

Biology Teacher

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32 Responses to Plant-tastic Chemical Signals

  1. Helen P. says:

    What a fascinating topic! Though your parents may not be able to *squash* the insect problem, I can testify first hand that their vegetables are top notch. Great blog!

  2. Tammy M. says:

    Thank you berry much!

  3. Shafaa M. says:

    Tammy, lettuce hope that over thyme the plants in your garden will be able to overcome this obstacle! And nice job on your blog, I enjoyed reading this unique perspective of plants that I previously never would have thought of before.

    • Mr. Mohn says:

      You ladies are a bushel of fun! Too bad all these garden puns don’t work as a natural pest control. We’d have enough to supply the entire Johnson County area.

      Just don’t start making soil puns. They’re too dirty.

  4. Helen P says:

    I have to say, weed make a great gardening team! I’d love to stick around, but I’ve had a long day, I’m beet!

  5. Shafaa M. says:

    Now Mr. Mohn, that would be a pretty rootless thing to do if you ask me…

  6. Mr. Mohn says:

    This has been a fertile discussion, but is it time to bury it?

  7. Helen P says:

    Well, I sure wouldn’t want to leaf anyone hanging..

  8. Shafaa M. says:

    Exactly Helen! And we’re having such a grape time with this, I mean, it is afterall further blossoming the scientific process.

  9. Lauren M says:

    Chive got a feeling these comments could go on forever…

  10. Helen P says:

    Chive got a feeling that we could harvest these puns all night!

  11. Shafaa M. says:

    It would seem a-pear-rantly so!

  12. Tammy M. says:

    Wow I carrot believe I missed out on all the fungis! You really beet me to it.

  13. Helen P says:

    I’m seriously digging these puns. Glad you could join us to help cultivate this discussion, Tammy.

  14. Tammy M. says:

    Thanks Helen. We’re really raisin the bar for garden puns 🙂 Any idea how long dill we stop?

  15. Shafaa M. says:

    It’d be a pit-i-ful shame if this wondrous blog strand would ever stop.

  16. Helen P says:

    In my op-onion, Mr. Mohn should get a raise in his celery for having to deal with all these puns!

  17. Tammy M. says:

    Luckily, there are planty of puns leaft!

  18. Tammy M. says:

    True, he has bean dealing with these radish puns for quite a long thyme.

  19. Shafaa M. says:

    Yeah, our mango-nificent use of punnery is definitely outnumbering Mr. Mohn, he’s speachless it appears so.

  20. Helen P says:

    I have to say, this pun adventure has been a chloro-blast!

  21. Mr. Mohn says:

    This has been a fruitful diversion from grading exams, but the last few puns are over-ripe. They’re just getting so corny.

  22. Shafaa M. says:

    Oh whoa, a connection to the cell unit! And to think I thought there was not mushroom for that…

  23. Tammy M. says:

    Yeah, thanks shallot for bringing that up. We don’t have mushroom for artichoke-worthy puns…

  24. Mr. Mohn says:

    Then again, it was nice to see all of you turnip for some actual conversation. We need to orange another “punny” topic in the future.

  25. Tammy M. says:

    Shafaa, we used the same pun! You know as they say, grape minds think alike.

  26. Helen P says:

    It is unfortunate to see this experience draw to a (glu)close, what an enlightening experience this has bean!

  27. Mr. Mohn says:

    Peas out, everyone!

  28. Shafaa M. says:

    Aha Tammy, Indeed. And yes Mr. Mohn, that needs to be done as people take these blog opportunities for pomegranted when they really could be having a cherry good time.

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