book review

Communica­tion in Plants:
Neuronal Aspects of Plant Life
F. Baluška, S. Mancuso, D. Volkermann, eds.
Springer, 2006 (438 pages)
Reviewed by
book cover image

I f only we could understand plants better, say the editors of this fascinating and provocative book, they might reveal to us something of the great mystery of life. Scientists have discovered that plants are not just passive green things, but they are complex organisms whose functions we barely understand. At the biochemical level, plants have intricate signaling pathways with many of the same elements as neurons in the brain, including neurotransmitters. At the cellular level, too, they have a system for sending signals to other parts of the plant to control their physiology. As the editors of this book remind us, action potentials, which are the electrical signals that convey information through our brains, were first discovered in plants, "Oh no, not again." -- petunia plant in Douglas Adams' Hitchhiker's Guide to the Galaxy where they control basic plant functions such as photosynthesis and phototropism. The idea that plants might have a rudimentary nervous system has met a great deal of resistance from biologists. Only now, say the authors, is the field of "plant neurophysiology" beginning to be recognized as a legitimate discipline.

Some of the authors also compare the roots of plants to the human brain. Plant roots can also recognize certain types of bacteria, and adapt them to provide nitrogen to the plant--a form of "domestication". When plant roots are attacked by insects, the roots release volatile chemicals that attract a particular species of nematodes that kill these predators. Plants even warn their neighbors, using volatile chemical signals, when they are injured. Different types of injury produce different signals, and the recipients of these messages adjust their physiology to protect themselves against the danger. This is unquestionably a form of communication. It's not too much of a stretch to call it a language.

As psychologists tell us, all behavior is communication, if another organism perceives it; but not all communication is behavior. If our plant brethren possess a nervous system, can they feel pain? Could plants even be conscious? The editors of this book, František Baluška, Stefano Mancuso, and Dieter Volkmann, are not new age cranks, but respected professors of botany at major universities, as are the many contributors. This is not the work of a bunch of new age neo-pagan tree-hugging Druids, but a serious scientific work. The articles are highly technical and require a background in biochemistry to fully understand. But the subject matter--green plants as intelligent organisms, trees using a complex chemical language to warn their comrades of danger, and so forth--seems like the stuff of science fiction.

However, despite the hype from the editors and some of the authors, calling the roots of a plant a "nervous system" would be considered by most scientists to be an exaggeration. Plants do not really learn, except in the most rudimentary sense. If learning were just a long-term change in response to the environment, as the book describes for plants, practically everything on the planet could be said to be capable of "learning". The articles describe some interesting experiments, and the authors strain mightily to fulfill their task of comparing plant signaling to animal nervous systems, at the expense of biochemical detail. The hype about plants having a nervous system may help keep non-biologist readers from falling asleep, but researchers interested in plant biochemistry, and lay readers who are just curious about whether plants are conscious beings will have to look elsewhere.