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A Plant That Can Smell
BlueCup writes "The question of how a dodder finds a host plant has puzzled researchers. Many thought it simply grew in a random direction, with discovery of a plant to attack being a chance encounter. But the researchers led by Consuelo M. De Moraes found that if they placed tomato plants near a germinating dodder, the parasite headed for the tomato 80 percent of the time. And when they put scent chemicals from a tomato on rubber, 73 percent of the dodder seedlings headed that way. Turns out, it sniffs out it's prey."
A dodder is also known as a Cuscuta.
Be relentless!
Somehow I think that plant pathologists have probably noticed this for decades. It a pretty useful lab plant for moving pathogens between plants in interesting ways. Dodder is grown in plant path greenhouses commonly and usually near host plants.
The way I heard it was: Two plants of the same species were placed in a room with the sensors attached. A man walked in and brutally hacked one of the plants apart and then left. After that, the surviving plant gave off the 'fear' signal whenever people walked in the room. Or something like that.
http://www.npr.org/templates/story/story.php?story Id=6160709
Plants send all kinds of signals. The problem is that this urban legend has to interpret those signals without much of any interaction from the plant. When I first heard of it, it was being used by people trying to counter vegetarian's arguments about how animals feels when they are butchered(sometime in the 70's).
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The story goes that scientist conected an EKG machine and watched for signs of brian patterns. When the plant apeared excited they interpreted it as emotion. I didn't think it was actualy true but i found a few posts about it.
http://skepdic.com/plants.html
http://forums.teamphoenixrising.net/showthread.ph
Take them with a grain of salt.
Hmmm, nice that the article doesn't mention the actual author of the paper (published in Science). Also not surprisingly, the actual paper doesn't talk about 'smell'. Oh and for the person going on about sample size, of course the paper gives sample sizes.
6 4.pdf
Here's the abstract:
Volatile Chemical Cues Guide Host Location and Host Selection by Parasitic Plants
Justin B. Runyon, Mark C. Mescher, Consuelo M. De Moraes*
The importance of plant volatiles in mediating interactions between plant species is much debated. Here, we demonstrate that the parasitic plant Cuscuta pentagona (dodder) uses volatile cues for host location. Cuscuta pentagona seedlings exhibit directed growth toward nearby tomato plants (Lycopersicon esculentum) and toward extracted tomato-plant volatiles presented in the absence of other cues. Impatiens (Impatiens wallerana) and wheat plants (Triticum aestivum) also elicit directed growth. Moreover, seedlings can distinguish tomato and wheat volatiles and preferentially grow toward the former. Several individual compounds from tomato and wheat elicit directed growth by C. pentagona, whereas one compound from wheat is repellent. These findings provide compelling evidence that volatiles mediate important ecological interactions among plant species.
And here's the actual paper for those with access to Science articles:
http://www.sciencemag.org/cgi/reprint/313/5795/19
Si hoc legere scis nimium eruditionis habes.
Actually, IIRC, plants don't actually follow strong light. Light inhibits growth strangely enough. So plants don't follow the sun, it's just that the lighted side of the plant grows at a slower rate than the darker side, thus causing the plant to curve toward the light. At least, that's how I've always understood it.
While I might agree that plant's "grow" at a slower rate in more intense sunlight, I don't believe it's proper to say that sunlight inhibits growth. What happens is that when a plant is in sufficient sunlight, it can devote its nutrients to growing heartier rather than "bigger." Plants in sufficient sunlight tend to be short, but also have thicker stalks and fuller (though fewer) leaves. Plants in low light grow taller and lankier, because they are a) trying to maximize their surface area to most efficiently absorb as much sunlight as possible, both through sheer size and by producing more leaves, and b) potentially grow taller than whatever is obstructing their ability to get to the light (think of a bunch of plants all in close proximity on the ground. The taller the plant, the less likely it is to be oovered up by another plant. So if a plant is not getting enough sunlight, it's possibly because all the other plants around it are taller than it. Therefore the best response is to get even taller still).
I don't have any studies, but I believe I've seen plants that shifted significantly after a change in the direction of the source of light (such as if you turn the plant 180 degrees after being in front of a window), a shift that occurred much too quickly to be explained away by the speed at which different sides of the plant grew.
Ok flame-proof suit on, but "it's" is short for either "it is" or "it has". In this case the apostrophe isn't needed to denote ownership any more than you need an apostrophe in the words 'his' or 'hers'. More info at the Apostrophe Protection Society.
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