To protect themselves from hungry caterpillars, a tomato plant was shown to release chemicals that make it taste terrible to the caterpillars. The chemicals are so upsetting to the caterpillars that they decide to eat other caterpillars instead.
The research team who discovered this, sprayed the tomato plants with methyl jasmonate (which the plants produce in response to stress) to trigger defense mechanisms. The chemical acts as a signal, causing the plant to alter its chemistry, resulting in a plant that was much less appetizing to the caterpillars. The methyl jasmonate also can attract enemies of caterpillars like predators and parasitoids which will eat the herbivores.
So a tomato plant is being eaten by caterpillars and releases a chemical to warn the other plants and the other plants respond by releasing toxins that cause the caterpillars to become cannibalistic and eat each other instead of the plant. So the plants are communicating with one another and working together to alter the behavior of the caterpillar. The result is apparently larger stressed caterpillars nibbling on smaller caterpillars nearby causing some disgusting oozing.
What’s especially disturbing is the caterpillars seem to still revert to cannibalism even when other plant options are nearby. Why disperse farther when you could just eat a closer, unlucky smaller caterpillar I suppose.
Also congrats to that lucky undergrad who helped conduct this research and already got his name on a nature paper.
Listening for munching
In more amazing ways plants are able to ward off caterpillars, some plants seem to even respond to the vibrations of herbivory. the cabbage butterfly caterpillar munching the leaves an Arabidopsis plant results in the leaf moving up and down a miniscule amount. These vibrations were able to be recorded and played back to the plants so the scientists could compare plants left in silence to plants exposed to munching sounds (but no actual physical damage). The plants that were in the presence of the recording of chewing vibrations created an increased amount of mustard oil. Mustard oil is used as a defense against herbivores.
So just listening to the munching even with no caterpillars present somehow makes the plants better able to ward off future attacks.
The plants were exposed to other vibratory sounds none of which triggered any response. They have absolutely no idea how this works but it definitely provides more evidence that plants are amazingly adept to responding to all kinds of stimuli and information in the environment despite having no brains and being underestimated by basically everyone in science who is not a botanist.
- John Orrock, Brian Connolly, Anthony Kitchen. Induced defences in plants reduce herbivory by increasing cannibalism. Nature Ecology & Evolution, 2017
- Plants respond to leaf vibrations caused by insect herbivore chewing. M. Appel, R. B. Cocroft. July 2014