A friend asked my view, so I read the recent article by Michael Pollan in the New Yorker, "The Intelligent Plant."
Many of the scientists in [Gagliano's] audience were just getting used to the ideas of plant “behavior” and “memory” (terms that even Fred Sack said he was willing to accept); using words like “learning” and “intelligence” in plants struck them, in Sack’s words, as “inappropriate” and “just weird.” When I described the experiment to Lincoln Taiz, he suggested the words “habituation” or “desensitization” would be more appropriate than “learning.” Gagliano said that her mimosa paper had been rejected by ten journals: “None of the reviewers had problems with the data.” Instead, they balked at the language she used to describe the data. But she didn’t want to change it. “Unless we use the same language to describe the same behavior”—exhibited by plants and animals—“we can’t compare it,” she said.I agree that we should use the same language to describe the same behavior, and applying the words 'behavior' and 'learning' to plants make sense to me. That we use these terms (appropriately, I think) for robots and computers points out that they are neutral with respect to mechanism. However, I don't think that 'intelligence' or 'consciousness' would be appropriate for anything described in this article. The prefix 'neuro' refers to neurons or the nervous system and we know for a fact that plants have nothing like neurons. It's pretty clear that multicellularity evolved independently in plants and animals, and there are important differences, so I find it highly unlikely that plant and animal behavior shares underlying mechanisms. Thus I very much doubt that there is “some unifying mechanism across living systems that can process information and learn.” While fundamental processes common to all life are no doubt shared, more sophisticated signaling is unlikely to be the same. Cell walls make it hard to see how information could be possibly be transmitted through synapses, which are specialized points of contact between neurons. On the other hand, plasmodesmata, channels that allow direct but reguated transport between cells, provide plant cells with the potential for mechanisms unavailable to animal cells. Thus, while communication between the parts of a plant is likely to be as sophisticated, if not more sophisticated, than comparable mechanisms in animals, it is very different, and much less well understood. We would do better to appreciate plants on their own terms. I hope that this article leads more young people into the exciting field of plant signaling. I fear that it may do so for the wrong reasons.