Today’s must-read: the social life of plants

by Caroline Brown

Did you see this article in the NYT yesterday? (Warning-registration may be required.) Canadian researchers are examining the ability of plants to distinguish members of its own species from “outsiders.” Last summer scientists at McMaster University in Hamilton, Ontario published a study on the sea rocket (Cakile edentula), a native member of the mustard (Brassicacaea) family that grows above the high tide line on sandy beaches.

Yet scientists have found evidence that the sea rocket is able to do something that no other plant has ever been shown to do.

The sea rocket, researchers report, can distinguish between plants that are related to it and those that are not. And not only does this plant recognize its kin, but it also gives them preferential treatment.

If the sea rocket detects unrelated plants growing in the ground with it, the plant aggressively sprouts nutrient-grabbing roots. But if it detects family, it politely restrains itself.

The finding is a surprise, even a bit of a shock, in part because most animals have not even been shown to have the ability to recognize relatives, despite the huge advantages in doing so.

If an individual can identify kin, it can help them, an evolutionarily sensible act because relatives share some genes. The same discriminating organism could likewise ramp up nasty behavior against unrelated individuals with which it is most sensible to be in claws- or perhaps thorns-bared competition.

Pretty cool that sea rocket can distinguish between its family members! (That’s a photo of it at right.) Dr. Dudley and his colleagues have since then discovered evidence that three other species can do the same thing, but in different ways.

Plants’ social life may have remained mysterious for so long because, as researchers have seen in studies of species like sagebrush, strawberries and thornapples, the ways plants sense can be quite different from the ways in which animals do.

Some plants, for example, have been shown to sense potentially competing neighboring plants by subtle changes in light. That is because plants absorb and reflect particular wavelengths of sunlight, creating signature shifts that other plants can detect.

Reserachers also studied a certain parasitic weed called dodder (genus Cuscuta, absolutely terrible vampire-like plant, maybe I’ll do a post on it one day). Dodder can “sense” chemicals released in the air by nearby plants and use it to “sniff out” its victim:

Scientists also find plants exhibiting ways to gather information on other plants from chemicals released into the soil and air. A parasitic weed, dodder, has been found to be particularly keen at sensing such chemicals.

Dodder is unable to grow its own roots or make its own sugars using photosynthesis, the process used by nearly all other plants. As a result, scientists knew that after sprouting from seed, the plant would fairly quickly need to begin growing on and into another plant to extract the nutrients needed to survive.

But even the scientists studying the plant were surprised at the speed and precision with which a dodder seedling could sense and hunt its victim. In time-lapse movies, scientists saw dodder sprouts moving in a circular fashion, in what they discovered was a sampling of the airborne chemicals released by nearby plants, a bit like a dog sniffing the air around a dinner buffet.

Then, using just the hint of the smells and without having touched another plant, the dodder grew toward its preferred victim. That is, the dodder reliably sensed and attacked the species of plant, from among the choices nearby, on which it would grow best.

“When you see the movies, you very much have this impression of it being like behavior, animal behavior,” said Dr. Consuelo M. De Moraes, a chemical ecologist at Pennsylvania State University who was on the team studying the plant. “It’s like a little worm moving toward this other plant.”

The movie that she’s referring to? YOU HAVE TO SEE IT! Go to the NYT article link and scroll down until you see the link for the movie. It’s worth getting an account to see it if you don’t have one (it’s free). The movie a time-lapse of a dodder seedling putting the moves on a tomato plant that it’s in the pot with it. (A still from the movie is at the top of the page). It truly looks like it’s sniffing the tomato plant out as it looks for its next victim.

Plants sure is crazy peoples!


6 Comments to “Today’s must-read: the social life of plants”

  1. How interesting is that! Goes to show our little green pals are smarter than perhaps we gave them credit for. G 🙂

  2. I wonder if we can recruit a whole bunch of these plants to attack GM Monsanto products….

  3. That is absolutely fascinating. I had no idea although now, come to think of it, I get the feeling that creeping jenny has the same ability. It always tries to strangle out neighbouring perennials. Finally removed it from around the pond.

    And to think the research was undertaken in the NWT. Cool!

  4. If this is true it will change the way we look at plants forever. Thanks for linking to the article.

  5. Is this the same principle behind why plants and flowers tend to grow towards sunlight? It’s curious that they’d be able to tell the difference between plant species, considering they have no senses to be able to do that.

    Robert (“Bobby”) from How To Build Greenhouse

  6. Interesting article. This will really change the way we look at our plants. Thanks!

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