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."
I was hiking with my parents in the Shining Rock Wildnerness, an area in western North Carolina. Part of the wilderness was burned out sometime in the 1920's and the burn formed a long lasting grassland along several peaks. We hiked it sometime in the early 90's and it was the first time I saw dodder. It was this strange mat of oranged colored leafless vines, much like this growing on a particularly plant (very similar to what is in the photograph, I believe). The strange thing is that we had hiked this trail over many years and had never seen this before. So we wondered at first if it were some new invasive species from elsewhere. Turns out that this was native to the area, but for whatever reason it never had grown this prolifically before. Definitely one of the strangest plants I've ever run across.
Even *single-cell* flagellates have what can be considered a rusimentary sense of smell, and the capability of changing their locomotion in order to lead them to food. That sort of ability is present all the way up through the multicellular ladder, and "smell" (or response to airborne chemical signals) have been well-known for quite some time in plants.
Frankly, I'm susprised that they didn't start out with an assumption that smell was involved.
steve
Oh, you're not stuck, you're just unable to let go of the onion rings.