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ForgetmenotsA Brief Stroll Down Memory Lane

Previously, we delved into the subject of “long-term” (weeks to months) plant “memory” by exploring what’s new on the subject of vernalization, that is, how some plants “remember” that they have experienced winter.

In this case, a “cold” treatment of some plant species over the course of weeks leads to the suppression of the expression of a gene that codes for a protein that inhibits flowering. Because this gene suppression is due to an actual physical, but epigenetic, modification of the plant cells’ DNA, it remains in place even after multiple cell divisions, though not after meiosis.

I’ve also recently posted about how plants may erase their “memories”.

But in my wanderings through the recent plant scientific literature on the subject, I bumped into a old, but familiar, title: Secret Life of Plants. (Please see ref. 1 below)

If you were a college student in the 1970’s, then you probably are familiar with the book and the documentary film (if not, please see here and here, respectively).

Probably the most notable thing about the movie is that the soundtrack is by Stevie Wonder.

If you’d like to watch the whole movie on YouTube, please go ahead. We’ll still be here after you finish…..

….welcome back!

Short-Term Memory

The latest incarnation of the “secret life of plants” is courtesy of Prof. Stanisław Karpiński and colleagues at the Warsaw University of Life Sciences, Warsaw, Poland. They published a paper in 2010 (ref. 2 below) providing experimental evidence that Arabidopsis plants are able to “remember” and “react” to information contained in light, at least over the short-term (hours).

Well, these experiments got noticed by the BBC, which published an online article entitled Plants “can think and remember”. And, of course, this story went sort of viral on the internet.

Fortunately, the whole topic was more intelligently discussed a few days later on the Scientific American blog network by Ferris Jabr entitled “Plants cannot “think and remember,” but there’s nothing stupid about them: They’re shockingly sophisticated”, which I highly recommend. It’s an excellent post.

Anyway, Prof. Karpiński and colleague Dr. Magdalena Szechynska-Hebda followed up this paper a few months later with a review entitled “Secret life of plants” (please see ref. 1 below). There’s even a YouTube video of Prof. Karpiński presenting a talk called “Do Plants Think” at the 2011 TED conference in Warsaw. (But all of us who can not understand Polish are out of luck.)

ThinkerBriefly, the gist of the new “Secret life of plants” (ref. 1 below) is summarized by the authors in their Discussion section: “Our results suggest that plants are intelligent organisms capable of performing a sort of thinking process (understood as at the same time and non-stress conditions capable of performing several different scenarios of possible future definitive responses), and capable of memorizing this training. Indeed leaves in the dark are able to not only “see” the light, but also are able to differently remember its spectral composition and use this memorized information to increase their Darwinian fitness.”

Like many plant scientists, I get a bit uncomfortable with the terms “plant intelligence” and “plant thinking” because it sort of confers a level of sentience to plants, analogous to animals, which plants certainly don’t possess. (And, let’s face it, an iPhone may be more “intelligent” than most plants.)

Perhaps the most thoughtful discussion of “plant intelligence” has been provided by Prof. Tony Trewavas from the University of Edinburgh (please see ref. 3 below).

But a more concise take on the subject is from Jabr’s Scientific American blog post mentioned above: “A big mistake people make is speaking as if plants ‘know’ what they’re doing,” says Elizabeth Van Volkenburgh, a botanist at the University of Washington. “Biology teachers, researchers, students and lay people all make the same mistake. I’d much rather say a plant senses and responds, rather than the plant ‘knows.’ Using words like ‘intelligence’ or ‘think’ for plants is just wrong. Sometimes it’s fun to do, it’s a little provocative. But it’s just wrong. It’s easy to make the mistake of taking a word from another field and applying it to a plant.”

See also: The Roots of Plant Intelligence. (Video of TED talk by Stefano Mancuso.)

References

1. Karpiński S. and M. Szechyńska-Hebda (2010) “Secret life of plants: from memory to intelligence.” Plant Signaling & Behavior, Vol. 5, pp. 1391-1394. (Full Text)

2. Szechyńska-Hebdaa, M., J. Krukc, M. Góreckaa, B. Karpińskaa and S. Karpińskia (2010) “Evidence for light wavelength-specific photoelectrophysiological signaling and memory of excess light episodes in Arabidopsis.” The Plant Cell, Vol. 22, pp. 2201-2218. (Full Text)

3. Trewavas, A. (2003) “Aspects of plant intelligence.” Annals of Botany, Vol. 92, pp. 1-20. (Full Text)

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