Researchers Find Discriminating Plants

The "sea rocket" shows preferential treatment to plants that are its kin. Evolutionary plant ecologist Susan Dudley of McMaster University in Ontario discusses her discovery.

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MADELEINE BRAND, host:

This is Day to Day. I'm Madeleine Brand.

ALEX COHEN, host:

And I'm Alex Cohen.

Coming up, the question of who wrote a famous religious poem turns into a very unchristian battle.

BRAND: First, remember the 1970s? People talked to their houseplants, played them classical music. They were convinced plants were sensuous beings and there was that 1979 movie, "The Secret Life of Plants."

(Soundbite of movie "The Secret Life of Plants")

Unidentified Male: Only a few daring individuals, from the scientific establishment, have come forward with offers to replicate his experiments, or test his results. The great majority are content simply to condemn his efforts without taking the trouble to investigate their validity.

BRAND: Well, some thirty years later, things may have changed. Scientists now report that a weed known as the Sea Rocket makes animal-like decisions. Susan Dudley carried out the study. She's an Evolutionary Plant Ecologist at McMaster University in Ontario, Canada and what did you discover that the Sea Rocket was doing?

Professor SUSAN DUDLEY (Biology, McMaster University): Well, what I discovered is that the plants made a different shape. They changed how much they put into roots when they were grown with strangers sharing the same pot, but not when they were growing with their siblings. So, their whole, how they grow - their morphology - depends on who they are growing with and basically it shows that they can recognize their kin. And we think that this is an indication that they are competing less with their kin.

BRAND: They can recognize their relatives?

Prof. DUDLEY: Or maybe recognize strangers, we don't know?

BRAND: Well, this must have been pretty astonishing?

Prof. DUDLEY: It was astonishing. I mean it was - there's a lot of good scientific reasons to look for it, but it is always astonishing when you think something is happening, and it turns out - or you look for it and it turns out that it actually is there.

BRAND: Well, plants don't have a brain. They don't have eyes. They don't have a sense of smell, I don't think? So how are they able to do this?

Prof. DUDLEY: Well plants have a lot of ways of sensing the environment. They sense all sorts of things about the environment. And they while they don't have eyes, for example, they have photo receptors which let them sense things about the color of the light. And that is actually a really well-known way the plants can sense whether or not there are other plants around them. We think that this is probably a chemical cue. Some research I'm doing in collaboration with someone at the University of Delaware, Harsh Bais, shows that there's something - they put something in the liquid surrounding the roots that illicits this stranger response.

BRAND: And what good does it do the plant? Does it make it better able to live? To succeed?

Prof. DUDLEY: Well, what we think is that - you know, our hypothesis, working hypothesis, is that competition is costly for plants and that if that they can agree not to compete, they will all do better. But the only ones that they can basically agree with would be their relatives. So, it's a kind of...

BRAND: It sounds familiar.

Prof. DUDLEY: Yeah, no, that's why it's not sensitive new age guy kind of plants, but you know, plants that are out to get what they can. And in fact, this kind of agreement not to compete goes away when resources are scarce. You know, we had one study where we are writing up, that shows when resources are scarce, they'll compete as strongly with relatives as they will with anyone else.

BRAND: So, they are not actually thinking, they are just reacting to chemical inputs?

Prof. DUDLEY: Yeah, I don't - I don't feel any more guilt about eating salads then I ever did. I definitely don't think that they are conscious, but I think that they are sensing things about the environment and responding to those things and perhaps even taking multiple cues from the environment into account as they respond. So the presence of competitors, the nutrients, whether those competitors are kin or strangers.

BRAND: So, this was the humble Sea Rocket, which is basically a weed. Do you think that other plants do the same thing and maybe plants that are a little fancier? Or more advanced than the weed could actually do more things?

Prof. DUDLEY: Well, we've done this in a few other plants and what we are finding is that in three other plants that we looked for it, we did find it. Mind you we've looked in species where we thought we would find it. Species that are kind of weedy, that grow with their relatives very often, that are, you know, sort of set up where you would expect an evolutionary biologist to find that you grow with relatives and favoring relatives so therefore it'd be to the plants advantage.

BRAND: Susan Dudley, thank you very much.

Prof. DUDLEY: OK. Thank you.

BRAND: That's Susan Dudley. She's an associate professor of biology at McMaster University in Hamilton Ontario. She discovered that there is a social life of plants.

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