Companion Plants Communicate by Sound

By: Ann Northrup

Ann Northrup spent her undergraduate years at the University of Michigan, where she earned a Bachelor of Science in microbiology….

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Whether good ones or bad, it’s helpful for plants to know what kind of neighbors they have. Long established ecological theories have focused mainly on competitive interactions. Facilitation—where plants help each other—is increasingly recognized to be as important as competition in shaping plant communities. Examples of facilitation involving light, chemical, or touch signals are well known, but there is now evidence of another mode of communication, particularly among heterospecific plant companions.

Australian researchers devised an experimental chamber where they could block the known modes of communication between pepper seeds and test plants. When basil—anecdotally deemed to be a good neighbor to peppers—was grown in this special chamber, the germination rate of pepper seeds was better than when no plant was present, whether the known channels of communication were blocked or accessible. This suggests that a previously unknown mode of communication is being employed to detect the neighbor. When pepper plants were grown next to pepper seeds, seed germination rate was higher than the no-plant control only when the known modes of communication were accessible. These findings indicate the identity of neighbors as like or different influences germination timing and success. The existence of a subtle communication mode, hypothesized to be sound, allows a plant seed to detect its neighbors and its future competitive environment. It may be able to regulate its developmental responses early on so as to not waste energy on unnecessary growth or defense strategies.

BMC Ecology, 13:19